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Garage => Mechanicals => Topic started by: Jan S on 29 September 2020, 04:04 PM

Title: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 29 September 2020, 04:04 PM
I have a 1975 USA model 450 SE with an 6.9 engine (normally, the car comes with the 4,5 liter engine).

I'm having trouble with my k-jetronic. The car won't start.

I have tested the fuel flow return to tank (0 liter/ minute), the fuel flow to the distributor (about 3 liter per minute), the system pressure and control pressure with cold engine and 15 deg C ambient temp. (both 2,4 bar).

The pressures should be 5,2-5,8 bar and 1,1-1,5 bar respectively.

My hypothesis is that the pump is not delivering the required pressure, hence I need to replace the pump. But it's quite suspicious that the two pressures are identical.

Any idea why that is? Coincidence? Or is the WUR playing its game hear?

Help much appreciated. 
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: TJ 450 on 29 September 2020, 10:12 PM
Off the top of my head, 3L / min sounds ok for the pump. I’d be focusing on the FD, maybe a stuck metering piston? Blocked inlet screen?

Was the car running recently, or sitting for years?

Tim



Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 01 October 2020, 07:42 AM
I have a 1975 USA model 450 SE with an 6.9 engine (normally, the car comes with the 4,5 liter engine).

I'm having trouble with my k-jetronic. The car won't start.

I have tested the fuel flow return to tank (0 liter/ minute), the fuel flow to the distributor (about 3 liter per minute), the system pressure and control pressure with cold engine and 15 deg C ambient temp. (both 2,4 bar).

The pressures should be 5,2-5,8 bar and 1,1-1,5 bar respectively.

My hypothesis is that the pump is not delivering the required pressure, hence I need to replace the pump. But it's quite suspicious that the two pressures are identical.

Any idea why that is? Coincidence? Or is the WUR playing its game hear?

Help much appreciated.
Let's clarify some more.  You're saying that
1.  the fuel pump is delivering 3 L/min and,
2.  There is zero fuel being returned to the tank?

Can you elaborate on #2 more specifically?  The way I'm reading it is that the fuel return line is blocked.  If that's the case then you need to fix that before anything else.  Maybe look over this thread too.  The troubleshooting process is covered in some detail.
https://forum.w116.org/mechanicals/exact-fuel-pressure-test-hookup-help-needed-for-a-california-6-9/ (https://forum.w116.org/mechanicals/exact-fuel-pressure-test-hookup-help-needed-for-a-california-6-9/)
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 01 October 2020, 09:04 AM
Thanks to both of you for responding to my message - it's highly appreciated!

The car has been running and starting since I bought it (April 2019). I noticed a change in the pump over the summer 2020. With ignition on the pump started and after ca. 5-10 sec the pump's sound changed ... as if the downstream system was filled with fuel and the pump operating at a higher pressure (resistance in the system). When the sound changed I could go ahead and start the car with no problems. Without the change in sound the car wouldn't start. Over the summer I drove close to 3000 km and the change in pump sound went from 5 sec to 30 sec to 60 sec to "never". Currently I have no change in pump sound and the car won't start.

The 3 liters/ minute comes from the feeder that goes to the FD inlet. The pump delivers this amount through the accumulator (?), damper cage, fuel filter and pipes, i.e. resistance is fairly low I believe. Pressure of 2,4 bar is probably sufficient to deliver that amount.

When measuring the return-to-tank flow I measured at the FD-outlet, right after the main pressure regulator. A system pressure of 2,4 bar is probably not sufficient to activate the main pressure regulator, hence no return flow.

I believe the pump is ready for the bin?

And, the fact that system pressure and control pressure are identical makes me suspicious. Is the WUR not doing its job here?

I'm not experienced with k-jet. Learning as I go forward. It's all hypotheses at this stage.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 01 October 2020, 09:31 AM
If the pump is old/original to the car I would replace it for sure.  They are pretty cheap and this then gives you a baseline from pump perspective.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 01 October 2020, 10:01 AM
If the pump is old/original to the car I would replace it for sure.  They are pretty cheap and this then gives you a baseline from pump perspective.
Yeah, I agree.  But if that doesn't do the trick then get yourself a gauge and start down the path described in the other thread.  It's a sequential and systematic process.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 01 October 2020, 10:28 AM
Thanks to all of you for encouraging messages and tips!

I'll start with the pump (buy a cheap used one) and start testing the whole system (I have bought a gauge). I might even have to look inside the tank. Start back and work forward. When I know the general condition of the system I will start cleaning the tank (maybe?), replacing pump, filter, accumulator, ........ all depending on test results.

Look forward to going through the link above from Raueda1.

I'll keep you posted. Cheers.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 01 October 2020, 11:11 AM
With respect, buying a "cheap used" pump is false economy.  To have a true baseline you need a brand new pump.  How do you know if the used one is any good?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 01 October 2020, 03:39 PM
Yes, you have a point. It's just an option on the table to sort things out (e.g. tank inspection, system testing) before the new pump is installed.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 01 October 2020, 04:55 PM
Yes, you have a point. It's just an option on the table to sort things out (e.g. tank inspection, system testing) before the new pump is installed.
You're not the first person to go through all this and you won't be the last.  It seems like this fuel system stuff is always the same in the end, and you'll wind up checking/cleaning everything, start to finish.  If you haven't cleaned out the tank you might as well do it now.   Odds are remote that it won't have a lot of crap in it unless somebody already did it.  And replace all the rubber hoses back there.  The fuel return hose is often NG and can restrict backflow even if you can blow through it.  then you can start moving down the chain....    Good luck!
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: John Moore Sr on 01 October 2020, 06:22 PM
When is the last time the fuel filter was changed?  It could be restricting flow if partially plugged up. Another possibility (if the pump package is so equipped)  is the "Pressure Compensator" as MB terms it. This is a little inline device with a small metal line added into the filter inlet connection that connects to said "compensator",  then ties into the accumulator leak off line that connects to the inlet damper on suction side of fuel pump. It is my opinion that failure of this little device would cause a recirculation of fuel pressure back to pump intake.  There is no mention of this device, nor of it's intended function in any printed MB Service literature that I have seen.  It is possible that it may be referenced in the M100.985 engine service micro fiche.  Another possible low pressure inducing part could be the in tank strainer located in the bottom of the fuel tank. The inlet pipe to the fuel pump connects to the strainer. It has a hex head to facilitate removal with a 23??mm socket. Of course you have to unscrew the hose connection out of it, and if you are lucky the strainer will turn out with it also. Sometimes they will. Sometimes they don't. The tank has to be completely drained of fuel to perform this, and as usual use extreme caution while working with flammable fuel.  JMSr.
 
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: revilla on 01 October 2020, 10:16 PM
Wait a minute. Am i getting something wrong here?
There’s 3 l/min flow out of the pump. Why are we talking about replacing pump, filter, etc?
The car was recently running. Cleaning the tank???
If I understood well you have an engine that doesn’t start and your objective is to get it running, not to replace parts left and right for the fun of it, right?
If that’s the case, and ONLY if that’s the case simply remove, check and clean your main pressure regulator. You have 2,4 bars when it should be at 5,8. I bet you one or all of the 3 o-rings there are either broken or missing. No need to buy a full (expensive) unit. Nothing to do with the wur to answer your previous question.  Or, your return line might be clogged.
I would start there until you get fuel returning freely back to the tank and your system pressure is at 5,8.
Good luck
Ps.: sure, cleaning the tank is always a good thing. Replacing every part no doubt is a good idea too. But all depends on your own scope in your adventure with the car. You did a fuel flow test, was the fuel clean? If yes, leave the tank alone for now and put it in your ‘continuous improvement’ bag. Magic doesn’t exist with these systems, thinking you replace a part and BINGO your engine will start. There’s rather understanding of the functioning principles and TONS of fine tuning. Specially with the KJet, plug-and-play like modern semi-mechanics won’t get you there and your bill and frustration will reflect just that.
Robert
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 03 October 2020, 03:43 AM
Raueda1; thanks for good wishes. Yes, I guess I will go down that route - ending up cleaning and testing the whole thing.

John; the filter hasn't been changed in my ownership (since April 2019). The plan was to do it summer 2019, but no. I will change it for sure, but as long as the pump delivers 3 liter/minute at FD input, I believe the filter and the tank strainer is not the culprit (working hypothesis). Although the strainer is also on the list to be replaced. I need to read a bit more about the "pressure compensator", that's new to me. And yes, working with fuel requires certain measures, e.g. removing plugs to battery and avoiding electrical tools.

Revilla; the flow at FD input is ok (3 liter/minute), but the system pressure is too low (2,4 bar). Isn't that pressure too low for the main pressure regulator to be "activated"? As soon as the pressure reaches let's say 5,5 bar, the main pressure regulator will "move" and allow fuel to go back to the tank? That's why i believe the pump needs to be replaced.

My objective is to get the car started, then test and inspect the entire system. Then I will assess and decide which route to go.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: revilla on 03 October 2020, 04:20 AM
Hi Jan,

Yes, you’re correct.  But that’s assuming your main pressure regulator is in working condition.  If your main pressure regulator is missing or has broken o-ring(s) it will allow more fuel flow thus giving you a reading of 2,4 instead of 5,8.  That’s why I suggest to focus on the MPR until you reach your 5,8. I have never seen a pump capable of delivering 3 l/min and not able to develop 5,8 pressure. But this could be a 1st time (?).
Removing, checking and cleaning your MPR is much easier than changing the pump that could be perfectly operational.  That’s why I always start there. You might be also missing shims in the MPR, true, but again I have never seen an MPR even missing all shims that gives a pressure drop all the way down to 2,4.  I think a MPR with no shims (usually 2-5) gives you about 5 bar of pressure. 2,4 is definitely too low.
One more thing, it’s odd that your control pressure and your system pressure are both at 2,4. Too much of a coincidence. Please make sure your gage valve is positioned on the WUR side and not the other way around. This mis-connection will make your gage always read control pressure regardless of the valve operation (open or closed).
Please let us know your findings. We’ll get there.
Regards
Robert
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: revilla on 03 October 2020, 04:44 AM
The spec calls for 1 l/30 secs, or 2 l/min minimum. The pump demonstrated flow is 3 l/min thus I believe your pump is OK. 
Again, all depends on your own personal objective. If you just want to replace parts with new that’s ok too. I just thought you wanted to start the engine.  Changing the filter doesn’t hurt either. But I doubt that’s the problem causing the difficulties to start the engine. I could be wrong of course.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 03 October 2020, 10:50 AM
Revilla; thanks so much for swift reply and good advice.

Valve is on WUR-side. I agree - it's too much of a coincidence that the system pressure is equal the control pressure. Something is going on there ....

I measured the flow of 3 liter/minute when de-connecting the fuel supply at the FD inlet. That means flow is coming directly from the rear system without passing through the FD. The pump works against less resistance, hence higher fuel flow can be delivered at lower pressure (pump curve - pressure as a function of volume - high pressure and low volume vs. low pressure and high volume). I assume ...

The flow at the FD-outlet "return-to-tank" is zero. Nothing is going passed the MPR at 2,4 bar. I would assume the pump would reach its "dead-end" pressure which is probably 6-7 bar if the flow back to the tank was close to zero. But no - it's 2,4 bar.

Is taking out the MPR straightforward? Anything special to be aware of? O-rings that has to be changed etc.?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: revilla on 03 October 2020, 11:16 PM
Hi Jan,

The most interesting observation is the zero return at FD outlet. I want to be optimistic, thinking your FD internal organs aren’t damaged.  But first, let’s remove the MPR. It’s quite simple actually.  The hypothesis is the following. Injectors opening pressure is between 3-3,5 bars depending on their condition. You have only 2,4 so they won’t open. Thus engine can’t start.  Later when possible can you please take a picture of your gage connections?

It’s not at all difficult to remove the MPR.   On the front/upper side of your FD you’ll see a 16mm (or 17?) nut. That’s your MPR. Reconnect the return line. Run the pump until you have your 2,4 bars. Unscrew the MPR but VERY slowly while watching the gage. What does it measure while you unscrew it? The assembly should come out after 5-7 turns. Do not unscrew it completely. Now your gage should be at zero as you have lost some fuel.  Right? If not at zero stop immediately.  Then unscrew the inlet line a few turns until you have zero in your gage.  Re-tight. Back to MPR, unscrew completely. Delicately remove it from slot. Sometimes the piston comes out and sometimes it doesn’t.  If piston (not magnetic) doesn’t come out give the pump a MICRO pulse keeping a rag close enough to the opening. You should now see the piston.
Take a picture of the MPR and share please.  Reinstall the MPR but WITHOUT the piston. Disconnect the return line. Give the pump a short pulse while keeping a rag and suitable container under the FD outlet.  Fuel coming out now? I hope so! If not, we have a major situation unfortunately. Remove the MPR again. Reconnect the outlet line. Micro pulse to the pump. Capture the exiting fuel. Observe. Any rubber or particles coming out? Do you have clean fuel flowing out of your (removed) MPR slot?

Please report back.  We’ll get into the MPR itself at the right time, but FIRST it’s key to understand the zero return flow and the 2,4 system pressure.

Regards

Robert

Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 04 October 2020, 03:05 PM
Thanks a lot, Revilla!

It may take a few days before I can test according to your advice. I will get back to you on that.

It's interesting that you think the pump is not at fault or at least not the first thing to attack, when zero return flow and 2,4 bar system pressure. Can you elaborate on that?

Back in a few days.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: revilla on 04 October 2020, 11:43 PM
Hi Jan,

The pump might be faulty, certainly. But based on your flow test it demonstrated 3 l/min which is beyond the spec value of 2 l/min. I understand your test was done so fuel didn’t go through the FD (measuring at inlet hose rather than at return line). Still 3 l/min sounds like a healthy pump. The fact you’re getting zero flow at the return line indicates there’s a problem with the FD itself.  It could be your MPR or the internals. I share with you it’s a mystery why you’re getting 2,4 bars with no flow at the return line. That’s why we need to understand how you connected the gage and also the condition of your MPR.  The test recommended before without piston will tell us a lot.  Another easy test you could perform to rule out a faulty pump is to connect one end of your gage (valve closed of course) to the inlet hose at FD and briefly run the pump to measure her ability to raise and maintain pressure.  This test will tell us whether the problem is with the pump (which I doubt) or rather with the FD. Again, this test is more practical than buying and replacing the pump. But if you want to buy/install a pump to check if your car would start that’s valid too.  It’s just a dart in the dark based on the fact it showed 3 l/min.  I prefer always to do the most practical tests first before buying/replacing parts and crossing my fingers.  A pump capable of producing of 2,4 bars of flow pressure is MORE THAN SUFFICIENT to get fuel out of the outlet port. That’s why I believe the issue is rather the FD/MPR than the pump.

Please let us know your findings. We’ll get your engine started. I’m confident.

Regards
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 10 October 2020, 08:09 AM
Finally I managed to squeeze in some garage time today.

I had to rebuild my fuel pressure tester in order to test the fuel pressure (system pressure) at the feeder (input to the fuel distributor).

The result: as I expected the pressure was 2,4 bar - identical to the system pressure I measured between FD and WUR when valve closed on WUR side of gauge.

The system pressure should be 5,2-5,8 bar.

My hypothesis is that the fuel pump must be replaced. What do you think?

An observation: the fuel pressure dropped from 2,4 bar to 0 bar immediately after ignition and pump off. Accumulator shot as well?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: revilla on 10 October 2020, 08:44 AM
Hi Jan,

Well done. Confirmed, pump must be replaced. Nothing like real life test/data to drive smart decisions.

Regarding the accumulator question. As your pump is kaput you MIGHT be loosing pressure back to the tank through the bad pump itself. It acts as check valve to prevent fuel return to the tank. It doesn’t necessarily mean your accumulator is bad. It rather means it can’t do its job if the pump doesn’t hold the back pressure. But it could be leaking internally in which case you would have to replace it too.
My suggestion is that as you’re disassembling the fuel pack to remove the pump, you should take advantage and test the accumulator to confirm/rule out its condition before buying a new one. Unless you want to replace it together with the pump as a preventive measure because you might not know when was it last changed. That’s totally acceptable and up to you, again depending heavily on your personal scope with the car. BTW, change the filter too as they really inexpensive these days. That wouldn’t hurt.  One area to be VERY CAREFUL is the tubes/banjo connections linking pump/filter/accumulator assembly. They are notorious to bend under tool pressure  which will certainly lead to a MUCH BIGGER leaking problem.  Washers as cheap/simple as they look are an important piece if the puzzle. Replace all with new please.

Good luck.

Robert

Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 10 October 2020, 09:47 AM
Thanks for your advice, Robert

Yes, I will disassemble the entire fuel pack and replace pump and filter and all rubber hoses (also in engine bay) , clamps, washers and maybe accumulator. I'm not sure about the inner life of the damper cage ... need to read a bit before I replace that as well.

How about installing a small fuel filter before pump? A filter with a glass/plastic housing to see what is coming out of the tank.

I'm even considering emptying the fuel tank, replacing strainer and inspecting tank. If tank is bad I probably need a new one. One step at a time.

 



 
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 10 October 2020, 12:39 PM
I would say draining the tank and checking it out is a very good idea, if your fuel supply is compromised then your system will never run right.  A pre - filter of sorts I would say is not really neccessary if your tank is nice and clean, those things are usually of plastic and that would make me a bit nervous to have it exposed to the elements.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 10 October 2020, 03:16 PM
A valid point, Daniel, regarding "the elements".

I have never emptied a tank before, looking forward to the mess, but even more so a clean fuel supply.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 12 October 2020, 10:41 AM
Since the whole back-end of the fuel system (pump, filter, etc.) is being replaced, I can add a fuel hose to the feeder in the engine bay and let the old pump do its last job. That should empty the tank, I assume  .
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Big Tiny on 17 October 2020, 07:17 PM
I have had a quick read through this thread.

Pump sounds fine, 3l a min is right on a new K jet pump. Also rules out tank blackage, filter, one way valve, supply line.

Something else is up, and that is likely the fuel distributor. FPR and WUR are ruled out with pressure test.

Check inlet fitting the FD ?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 22 October 2020, 10:59 AM
Hi Big Tiny,

I measured the flow 3 liter/min and pressure 2.4 bar at the feeder that goes into the FD, before it goes into the FD. The same pressure 2.4 bar (system pressure) I measured between FD and WUR when valve closed on the WUR side of the gauge.

The pump should produce 5.2-5.8 bar system pressure. According to my understanding the pump must be replaced - it can only "produce" 2.4 bar

I emptied the tank the other day. I will squeeze a few more drops out at the weekend before I start disassembling. I have to find a 46 mm socket to get the strainer out.

I look forward to looking inside the tank with a borescope.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 22 October 2020, 12:42 PM
Hi Big Tiny,

I measured the flow 3 liter/min and pressure 2.4 bar at the feeder that goes into the FD, before it goes into the FD. The same pressure 2.4 bar (system pressure) I measured between FD and WUR when valve closed on the WUR side of the gauge.

The pump should produce 5.2-5.8 bar system pressure. According to my understanding the pump must be replaced - it can only "produce" 2.4 bar

I emptied the tank the other day. I will squeeze a few more drops out at the weekend before I start disassembling. I have to find a 46 mm socket to get the strainer out.

I look forward to looking inside the tank with a borescope.

Please remember safety ;)  Do this in well ventilated space, even better with respirator.  Also have fire extinghuiser handy.  As one of my other Benz buddies would say:"the entertainment value of a car fire should not be dismissed out of hand" ::)
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Big Tiny on 22 October 2020, 05:44 PM
Hi Big Tiny,

I measured the flow 3 liter/min and pressure 2.4 bar at the feeder that goes into the FD, before it goes into the FD. The same pressure 2.4 bar (system pressure) I measured between FD and WUR when valve closed on the WUR side of the gauge.

The pump should produce 5.2-5.8 bar system pressure. According to my understanding the pump must be replaced - it can only "produce" 2.4 bar

I emptied the tank the other day. I will squeeze a few more drops out at the weekend before I start disassembling. I have to find a 46 mm socket to get the strainer out.


I look forward to looking inside the tank with a borescope.

OK, I missed that part.

Are you sure Gauge is working, just a thought.

Yes pulling tank and cleaning is a good maintenance item either way.

I use a low profile 46mm socket, like this.
 https://www.ebay.com.au/itm/Draper-Tools-Expert-46mm-3-8-Sq-Dr-ADblue-Filter-Socket/164087710912?hash=item263463c4c0:g:GAEAAOSwh7RfC7LA

Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 08 November 2020, 09:34 AM
The gauge is new, but I have not tested it/ calibrated it. Some uncertainty there, yes.

I emptied the tank by using the fuel pump and disconnecting the feeder at FD inlet. Went smooth. Jacking the car up and down completely emptied the tank.

I also disassembled the entire fuel system at the back. I expected a messy job, but not a drop landed on the floor. Hoses had started to crack on the edges, but the system in general looked clean and fairly ok but old. Damper cage was spotless, internally. I will reuse that one. All the rest will be replaced.

The strainer caused me some problems. It was tight. I used a standard 46 mm socket - which I had machined to remove the tapered edge on the socket and to get enough space for a breaker bar. But the strainer sat tight - I had to use a car lift jack to put enough pressure on the breaker bar. Finally it gave in.

And the strainer looks fairly ok after 45 years. But I will replace it.

Next is to use a borescope to inspect the tank.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 08 November 2020, 12:11 PM
Looking at the bottom of this tank screen I would say you have a "rust - o - rama" in that tank of yours :o
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 09 November 2020, 08:24 AM
Looking at the bottom of this tank screen I would say you have a "rust - o - rama" in that tank of yours :o
Sure enough.   More strongly than ever, based on this long adventure and that of countless others (including myself), I'm convinced that there's really just one way to deal with these old cars:  Remove, test &/or replace everything related to fuel, starting at the rear.  Just fixing/rebuilding/replacing one element is almost never enough, and it will just reveal a problem someplace else. 

Remain calm and carry on!
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Big Tiny on 10 November 2020, 02:15 PM
Yes tank screen is terrible.

No point even attempting anything else until this is fixed.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 10 November 2020, 03:28 PM
Borescope inspection tomorrow. Sleepless nights in front of me? We'll see ......

I cleaned the bracket today. I have ordered all the parts including new rubber buffers, bolts, washers, pump, filter, accumulator, hoses, strainer ....... everything.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 14 November 2020, 03:26 PM
Put the borescope inspection on hold, unfortunately - the equipment I borrowed was not EX-certified. Risk is too high. Shit can happen .......

I will probably go for this inline filter between tank and pump inlet, it's 14 mm or probably 9/16". Perfect for the hose.

https://mercedessource.com/store/1978-1985-bosch-gasoline-fuel-pump-protection-pre-filter

Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 22 November 2020, 02:06 PM
Things are moving slowly forward. Waiting for parts for the fuel system.

Yesterday I removed all fuel hoses in the engine bay. New ones will be SAE J30 R9 standard.

I have a non-original engine, and for some reason the previous owner has cut the metal fuel line between Fuel distributor/pressure damper and warm-up regulator and connected them with a 8 mm fuel hose with length 9 cm.

Inside the metal line one can see a hard-plastic hose.

- does anybody know the purpose of this hard plastic hose?
- what is the consequences of both the metal line and hard plastic hose being cut? Fuel will probably end up between the metal line and hard plastic hose along the entire length of the line .....

I might have to buy a new one .....
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 22 November 2020, 02:08 PM
See pic
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 23 November 2020, 10:52 AM
I am not clear what you mean, do you mean you now have a non - metal line running between the WUR and FD?  And then the cut metal pipe you show is what the previous owner did?  As far as I know that metal line has a sort of "baffle" inside.  This metal line is no longer available, and they are notorious for shearing off at the WUR because the line thins out a lot at the connector, so if it's rusty as is often the case most folks unfortunately shear off the line in an affort to remove the connector at the WUR.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 23 November 2020, 02:11 PM
I still have the metal line between FD and WUR, but a piece in the middle - approx 20-30 mm long - has been cut out (see pic). Hence the previous owner put in a fuel hose and two clamps to connect those two ends.

Inside the metal line you see a hard-plastic hose. Is that what you call a baffle?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 23 November 2020, 02:17 PM
... somehow I struggle posting pics .... an error occurs ....
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 23 November 2020, 03:48 PM
Inside the metal line you see a hard-plastic hose. Is that what you call a baffle?

Yes that would be the baffle.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 23 November 2020, 04:09 PM
Do you know the purpose of the baffle?

Any consequences of both the metal line and the baffle being cut?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 23 November 2020, 04:47 PM
Do you know the purpose of the baffle?

Any consequences of both the metal line and the baffle being cut?

Not sure really.  Perhaps to smooth out pressure variation in the line ???
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 24 November 2020, 07:25 AM
Do you know the purpose of the baffle?

Any consequences of both the metal line and the baffle being cut?
More pictures would help, to be sure.  I'm having hard time visualizing what's what.  Regardless, just curious, what year is the engine?  And what's the orientation of the WUR?  Most seem to face upwards, though some early ones (like mine) face sideways.  Significantly, the  fuel line constructions for the different WUR orientations aren't the same.  One of mine is nylon with a thick RUBBER sheath on the outside.  I  can't remember which one and car is in storage so I can't look.  But that line corresponds to your tube-inside-metal version. Maybe the tube-inside-metal version is just an upgrade from what I have.  I've wondered why one WUR line is so thick on the newer cars.  Maybe a fire precaution?  But then why the tube, not just metal?  This all seems to support the baffle idea.  But maybe we'll never know.  It's amazing to me how many dampers, baffles, etc there are on these cars.  Clearly there are lots of things going on that I can't comprehend.

Anyway, based on all that it seems like the tubing is there for some purpose.  Just connecting the metal tubing by splicing in fuel hose would seem to defeat that purpose. Under the circumstances I think I'd try to fashion a proper replacement for the whole thing.  Or, better still, find the real part someplace.  Good luck.  Eventually all this will get solved!  Cheers,
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 24 November 2020, 12:27 PM
Thanks to both of you for your assessment.

Engine is 100.985 (6.9), US version, left the production facility 7 Nov 1977. I will post a pic to show the WUR orientation.

Yes, I will try to find a used one. Won't be easy. At least fix properly.

1-2 weeks before I can assemble the new fuel system, hopefully (still waiting for some parts).
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 24 November 2020, 12:30 PM
See pic with fuel hose close to WUR.

I believe the WUR and FD and fuel pressure damper is next on my list of things to check/fix  :-\
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 24 November 2020, 01:57 PM
Not to confuse the issue at hand too much, but in the pic it looks like the plug connector on the WUR has been snipped off?  Maybe the pic is not clearly showing this.  Also, looking at the vacuum line connections on the WUR they look incorrect to me, but I am not sure if your WUR also has the altitidue compensating function, so maybe you have 2x vacuum connections on the bottom, in additon to the large vacuum connector at the top (currently in your pic there is no vacuum line connected here).  Also I see a plugged off orifice in the contour hose, so there seems to have been some tweaks in the vacuum connections.

As to the fuel pipe, yes I would source a good used one, I am not 100% sure if the rubber section will influence your fuel delivery but better to put the whole system back to baseline as much as you can.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 24 November 2020, 02:56 PM
Well spotted, daantjie!

The WUR is not the correct one (currently I have one for the W126 380-series and not W116 6.9, i.e. 0 438 140 056 instead of 0 438 140 010), and yes the plug connector on WUR has been snipped off and the vacuum lines are dubious, to say it mildly.

This will be the next area to focus on - WUR, FD, air valve and vacuum lines and fuel pressure damper with vent hose. But first I would like to start the car with the new "overhauled" fuel system (new pump, filter, tank strainer accumulator, hoses, washers, bolts, clamps).

Must be said: The car was running fairly nice - both cold and warm - before the pump failed (the accumulator had probably given up a long time ago).
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 24 November 2020, 04:36 PM
Wow, a picture's worth 1000 words.  Yes, everything Danielle said.  It also looks like the plug on the fuel cutoff switch isn't there either.  That's a real safety issue.

To be honest, I'd fix all that stuff before trying to start it.  It might start, it might not.  But if not you might just waste time and starter life by cranking it.  Also, the fact that it did run doesn't necessarily mean much, odd as that sounds.  These systems can sometimes be tweaked to run but that doesn't mean that they're running right.  Example:  when I got my car it seemed to run fine, more or less.  Sometimes a bit hard to start, but didn't seem major.  It turned out that the WUR wasn't working at all and somebody set the primary system pressure to = hot control pressure to get around the nonworking WUR.  It drove me crazy for some time.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: TNNBENZ on 25 November 2020, 09:00 AM
Hello,hello...........the plastic tube inside steel fuel line is for dampening the vibration from the fuel pressure, If you use an inline filter I would secure it very well because there is about 70lbs of fuel pressure minimum much of the time. I assume that is why filters r so big & metal.
I have a 1977 4.5L  and lots of stuff is the same but not all of course...there have been several revisions to the M117 fuel system,  I do not know if that pertains to ur 6.9. I was told to search in forum search "fuel Assembly" to find posts and it revealed no results 4 me.  Do you plan to rebuild ur fuel distributor & WUR ???
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 25 November 2020, 11:35 AM
Fantastic, thanks to both of you!

Raueda1; do you have a picture of "the plug on the fuel cutoff switch"? Where do I find it? What is the purpose? I expect the system to be tweaked and a situation similar to your previous situation i.e. WUR not working at all. I will do a new pressure test when the new rear fuel system is assembled.

TNNBENZ; great to know regarding the tube inside the steel line. I need to find a new-used one. Will be hard I guess. I have only one filter after the pump. Do you mean an inline filter between FD and WUR?

Yes, I'm planning on buying a new-rebuilt WUR and probably rebuilding the FD. And the vacuum lines need to be checked. And the air valve ....... but before all that I would like to hear the engine run.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 25 November 2020, 04:47 PM
Fantastic, thanks to both of you!

Raueda1; do you have a picture of "the plug on the fuel cutoff switch"? Where do I find it? What is the purpose? I expect the system to be tweaked and a situation similar to your previous situation i.e. WUR not working at all. I will do a new pressure test when the new rear fuel system is assembled.

TNNBENZ; great to know regarding the tube inside the steel line. I need to find a new-used one. Will be hard I guess. I have only one filter after the pump. Do you mean an inline filter between FD and WUR?

Yes, I'm planning on buying a new-rebuilt WUR and probably rebuilding the FD. And the vacuum lines need to be checked. And the air valve ....... but before all that I would like to hear the engine run.
I refer to the socket in pic below.  Yours is in the pic of your engine without anything plugged into it.  If I remember right it's connected to the fuel pump circuit, so that if the engine stops then the fuel pump shuts off.  If you crashed AND the engine stops AND there's a leaking fuel line, you don't want the pump running.  Below is the 6.9 engine wiring harness (or at least my harness).  All that stuff needs to be there for stuff to work right.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: TNNBENZ on 25 November 2020, 04:58 PM
I am awaiting a rebuild kit for my fuel dist. & WUR from this man at https://k-jet.biz/. He has impressed me with lots of information.  He sells rebuilt WURs 4 around $500. I think that is high but I am new to Mercedes. He has some good guides on his site.
The fuel filter comment about inline is in response to a post I just hurriedly skimmed and thought u said you were going to hook up a plastic see through filter, this why I said connect it extra securely !!! I may have read the post wrong........
My service manual states that between 77- 79, 4.5L fuel system changed the position of accumulator in front of fuel filter, added a compensating valve via an added hose. Light alloy dist. has it already installed. Also added a check valve, and capped center connection of accumulator, and increased hose to damper  fuel pump to 13mm from 10mm. This info is 4 a 4.5L, I do not know if it pertains to 6.9. I think it does but I am a novice learning quickly (Trying Hard) I want to find the post in this form but no one seems to help me much, and it does seems site does not have many active members as other forums I have been on... Do you have 13mm part numbers for hoses in the fuel assembly, that may work on 4.5L M117 engines...
I saw you mention 14mm somewhere on an earlier post...
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: TNNBENZ on 25 November 2020, 05:02 PM
Raueda1, is your great photo similar to a 4.5L engine ?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 25 November 2020, 05:07 PM
Fantastic, thanks to both of you!

Raueda1; do you have a picture of "the plug on the fuel cutoff switch"? Where do I find it? What is the purpose? I expect the system to be tweaked and a situation similar to your previous situation i.e. WUR not working at all. I will do a new pressure test when the new rear fuel system is assembled.

TNNBENZ; great to know regarding the tube inside the steel line. I need to find a new-used one. Will be hard I guess. I have only one filter after the pump. Do you mean an inline filter between FD and WUR?

Yes, I'm planning on buying a new-rebuilt WUR and probably rebuilding the FD. And the vacuum lines need to be checked. And the air valve ....... but before all that I would like to hear the engine run.
I refer to the socket in pic below.  Yours is in the pic of your engine without anything plugged into it.  If I remember right, it's connected to the fuel pump circuit, so that if the engine stops then the fuel pump shuts off.  If you crashed AND the engine stops AND there's a leaking fuel line, you obviously don't want the pump running.  Below is the 6.9 engine wiring harness (or at least my harness).  All the sockets/plugs/etc need into something or other for stuff to work right.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 25 November 2020, 05:10 PM
Raueda1, is your great photo similar to a 4.5L engine ?
Probably, but I can't say for sure.  It's just K-jetronic stuff and temp sensors I think.  Need wiring diagram....  But your car is 6.9 engine transplant to 450SEL, right?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 26 November 2020, 10:50 AM
raueda1; thanks for this safety advice. Another item on my to-do list.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 26 November 2020, 11:21 AM
TNNBENZ; thanks for the rebuilding tip. I need to assess the way forward when the fuel system is working.

Correct, I'm planning on installing an inline filter between tank and damper cage to avoid particles/dirt entering the pump. I'm waiting for this part to arrive: https://mercedessource.com/store/1978-1985-bosch-gasoline-fuel-pump-protection-pre-filter

This filter is for the 14 mm hose from tank to damper cage. I also bought a new 14 mm hose with part number 123 4700 875 to fit the inlet on the damper cage. See pic. The hose length is 225 mm. I believe you can also get a similar 12 mm hose. I believe part number is 116 4701 575.

I will cut out a 50 mm long piece of that hose (to install the inline filter) and use that piece from damper cage to pump inlet (also requires a 14 mm hose).

I have a 1975 4.5-chassi but with a 1977 6.9 hence I'm not familiar with the changes you refer to. Sorry.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 26 November 2020, 01:02 PM
I am awaiting a rebuild kit for my fuel dist. & WUR from this man at https://k-jet.biz/. He has impressed me with lots of information.  He sells rebuilt WURs 4 around $500.
1.   I think that is high but I am new to Mercedes. He has some good guides on his site.
The fuel filter comment about inline is in response to a post I just hurriedly skimmed and thought u said you were going to hook up a plastic see through filter, this why I said connect it extra securely !!! I may have read the post wrong........
My service manual states that between 77- 79, 4.5L fuel system changed the position of accumulator in front of fuel filter, added a compensating valve via an added hose. Light alloy dist. has it already installed. Also added a check valve, and capped center connection of accumulator, and increased hose to damper  fuel pump to 13mm from 10mm. This info is 4 a 4.5L, I do not know if it pertains to 6.9. I think it does but I am a novice learning quickly (Trying Hard) I want to find the post in this form but
2. no one seems to help me much, and it does seems site does not have many active members as other forums I have been on... Do you have 13mm part numbers for hoses in the fuel assembly, that may work on 4.5L M117 engines...
I saw you mention 14mm somewhere on an earlier post...
1.  Rebuilding the WUR yourself isn't too bad if you're slow and careful.  The FD is another matter.  The consensus seems to be that the cast iron FD can be a DIY rebuiild job, usually, if you're slow, careful and don't force things.  I did it and (now) it works great.  There are still dangers however, and if you make a mistake you can wreck your engine surprisingly easily.  I did that too.  :o
The aluminum FD is said to be much harder or impossible to do yourself.  Each port has it's own adjustment which can really only be set on a dedicated test bench.  Be prepared, at a minimum, to do fuel flow rate testing.  Frankly I'd have one of the pros do it.  I think most folks here in N America have used http://www.cisflowtech.com/ (http://www.cisflowtech.com/) .  But your guy may well fine, I dunno.  BTW, go out and get a fuel system pressure gauge if you haven't already.  You'll need to get the WUR (and everything else) set up right.  Do some searching here.  There's tons of info on it.

2.  As for the forum, activity goes up and down, like any other.  To be sure, the activity isn't like Benzworld or some others.  That said, it's been my experience that the technical level here is heads and shoulders above the other MB forums.  But the culture sometimes isn't as newby-friendly as some other sites might be.  It isn't that people aren't helpful, I think it's just assumed that everybody has all the manuals (or used the ones on this site), has read everything there is to read and is at their wits end.  That includes spending a lot of time searching and reading old posts.  There aren't many issues that somebody else hasn't already had so there might be a little stubborness about reinvneting the wheel.  But no worries, keep at it and keep posting.  You'll get there.  :)  Cheers,
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 14 December 2020, 03:58 PM
Things are moving slowly forward ..... today I received a new fuel line between the fuel pressure damper and WUR with intact inner plastic tube! Great stuff. See pic #1. You also see the damper -- by the way it was full of fuel and small particles). I probably need to buy a new one, it looked old.

The vent line from the fuel pressure damper was laying on top of the engine in the area under the FD. That seems a bit hazardous from the previous owner, I need to fix that.

Is this vent line supposed to go to the rubber hose that is connecting the air inlet with the valve cover? There is a small plugged opening (see pic).

Which way will the fuel go - to the valve cover or to the air inlet? I would guess to the air inlet .......

Any advice would be much appreciated.

Still waiting for other fuel assembly parts, it takes ages.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: rumb on 14 December 2020, 04:39 PM
The vent line can go either place. The rubber fitting or under the intake manifold.  There is a drain hole in the block to let anything that get in there out beneath the car.  Draining to the rubber hose it will either put gas in your oil or make your car run rich, neither things I would want. The EPA has different opinions.....
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 15 December 2020, 12:15 AM
Rumb; thanks for quick response. This is interesting.

Can you tell me a bit more about the drain hole in the block? Where do I find it? The idea is to guide the hose into this hole, or let the leaked fuel flow find its way into the drain hole?

Do you by chance have a picture of this drain hole?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 15 December 2020, 09:31 AM
Rumb; thanks for quick response. This is interesting.

Can you tell me a bit more about the drain hole in the block? Where do I find it? The idea is to guide the hose into this hole, or let the leaked fuel flow find its way into the drain hole?

Do you by chance have a picture of this drain hole?
It's about 1 cm dia and at the low point at the rear of the block in the "valley" of the V.  It's very close to the oil pressure gauge fitting.  It's very difficult to see with the intake manifold in place.  It's even more difficult to see if it has been obscured by years of junk, dirt, etc.  Mine was completely blocked with fuzz from what seemed to be an old mouse nest.  I was horrified.  Good luck!
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 15 December 2020, 10:49 AM
Thanks, raueda1

I will search for the drain hole at the weekend. I have currently access to a borescope, maybe that helps.

So the solution is to put the hose a few inches into the hole, and make sure it stays there? No fire hazard associated with this alternative?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 15 December 2020, 09:58 PM
Rumb; thanks for quick response. This is interesting.

Can you tell me a bit more about the drain hole in the block? Where do I find it? The idea is to guide the hose into this hole, or let the leaked fuel flow find its way into the drain hole?

Do you by chance have a picture of this drain hole?
It's about 1 cm dia and at the low point at the rear of the block in the "valley" of the V.  It's very close to the oil pressure gauge fitting.  It's very difficult to see with the intake manifold in place.  It's even more difficult to see if it has been obscured by years of junk, dirt, etc.  Mine was completely blocked with fuzz from what seemed to be an old mouse nest.  I was horrified.  Good luck!

Nice one Dave!  I did not even know about this drain hole.   I went and checked mine and it was gunky of course :o
The drain exits just aft of the sump on the driver side.  I saw this hole before and thought it was a bolt hole, who knew 8)
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 16 December 2020, 07:41 AM
Rumb; thanks for quick response. This is interesting.

Can you tell me a bit more about the drain hole in the block? Where do I find it? The idea is to guide the hose into this hole, or let the leaked fuel flow find its way into the drain hole?

Do you by chance have a picture of this drain hole?
It's about 1 cm dia and at the low point at the rear of the block in the "valley" of the V.  It's very close to the oil pressure gauge fitting.  It's very difficult to see with the intake manifold in place.  It's even more difficult to see if it has been obscured by years of junk, dirt, etc.  Mine was completely blocked with fuzz from what seemed to be an old mouse nest.  I was horrified.  Good luck!

Nice one Dave!  I did not even know about this drain hole.   I went and checked mine and it was gunky of course :o
The drain exits just aft of the sump on the driver side.  I saw this hole before and thought it was a bolt hole, who knew 8)
And you just completed the puzzle!  I never figured out exactly where the exit was, there was just dripping of solvents etc from someplace under the engine.  The whole damper design seems pretty cockeyed to me given that failure seems to risk hydrolock or engine fire.  Cheers,
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 17 December 2020, 01:48 PM
I searched for the drain hole today, without luck. I need to use a camera with USB to the pc, I guess.

Another try at the weekend.

raueda1; is it possible to take a photo and point in the right direction?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 17 December 2020, 02:10 PM
A great day today - all parts have arrived. The whole assembly is new - except damper cage, large bracket, small bracket for the tank hose and metal connection from accumulator to feeder hose/fuel line.

Notice the little pre-pump inline filter 14 mm next to the tank hose. Will keep the pump clean.

A few more things to check and clean and then we will fire up the old man. Exciting times .....
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 17 December 2020, 03:10 PM
Took some borescope pictures of the damper cage today (the inside).

It's an old Bischoff 116 470 0516". It's hollow :-)

Pic 1 shows the zylinder wall and the round surface. One piece of metal that is bend. Fairly clean.

Pic 2 shows the opposite side. Two metal pieces are connected. We can see some rust. Confirms that stainless steel can rust, as expected :-)

Pic 3 shows the 14 mm inlet port. Fairly clean.

Pic 4 shows the leak port from accumulator. Full of particles that will go straight into the pump.

I'm considering ultrasonic cleaning. The damper is not that bad, but I have never tried it before, and this might well be an interesting opportunity to test it.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 17 December 2020, 06:47 PM
I searched for the drain hole today, without luck. I need to use a camera with USB to the pc, I guess.

Another try at the weekend.

raueda1; is it possible to take a photo and point in the right direction?
This is the best pic I have and is the best I can do right now (car is in storage).  I'm pretty sure it was taken with engine removed from car.  Anyway, you can identify the oil pressure gauge line, circled in yellow, which is snapped off at the top.  The other larger tube is the brake booster line.  The red line follows the border between the block and transmission flange.  The plugged blue hose is where the heater hose would normally be.  Finally, the green scribble shows approximately where the drain is - except that it's under the intake manifold so not visible.  Again, it's very close to the rear of the block at the low point.  Very, VERY difficult to see.  I didn't even know it was there till I had the heads off and the block totally exposed for cleaning.  The bottom of the block "V" just collects dirt, grime, rust flakes, mouse nests and all manner of garbage.  The layer on my car was about 0.5 cm thick back there!  I guess the point is, that it might not be visible at all if it's clogged like mine was. Maybe a stiff, bent wire to probe around?  Good luck and cheers,
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 18 December 2020, 07:20 AM
Fantastic, thanks a lot!
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: ADV_rider on 26 February 2021, 01:54 PM
A great day today - all parts have arrived. The whole assembly is new - except damper cage, large bracket, small bracket for the tank hose and metal connection from accumulator to feeder hose/fuel line.

Notice the little pre-pump inline filter 14 mm next to the tank hose. Will keep the pump clean.

A few more things to check and clean and then we will fire up the old man. Exciting times .....

Neat!

JanS, could you please confirm the OD diameter of the damper and the fuel pump? the damper to fuel pump connection.
Mine is 15mm OD on fuel pump and 12mm on damper, which I find very strange and I cant find how to connect both.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 01 March 2021, 11:27 AM
Sorry, I didn't see this before now.

My damper with number 116 470 0516 has both inlet and outlet 14 mm. The leak is 6 mm.

My pump is Bosch for K-jetronic (the 6.9) with number 002 091 9701. Also 14 mm inlet.

See also my comments in your post.

I'm a small hose nipple away from firing up the system :-)
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: ADV_rider on 01 March 2021, 06:38 PM
Sorry, I didn't see this before now.

My damper with number 116 470 0516 has both inlet and outlet 14 mm. The leak is 6 mm.

My pump is Bosch for K-jetronic (the 6.9) with number 002 091 9701. Also 14 mm inlet.

See also my comments in your post.

I'm a small hose nipple away from firing up the system :-)


thanks
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 10 April 2021, 03:06 PM
PROBLEM SOLVED

W116 450 SE with non-original 6.9 and K-jetronic AND STARTING PROBLEMS.

Today was a great day - I finally installed the new fuel assembly (every piece is new except for the pressure damper and the bracket) and the car started immediately (after 7 months not running) with no leaks!

The reason why it took so long was that I wanted to install a pre-pump fuel filter (not original), and to do that I needed a 14mm 90 degrees double hose nipple. Not easy to get (I ordered this in early January).

Before starting the car today, I did some testing:

- Fuel flow out of the feeder from the rear that connects to the fuel distributor: 4 liter per minute
- Fuel flow at return to tank (after main pressure regulator): 1.75 liter per minute (spec says at least 1.5 liter/ minute I believe)
- System pressure: 5.2 bar (5.2-5.8 bar is the design spec)
- Control pressure cold at around 10 deg C: 1,0 bar (spec says 0.7-1.1 bar)
- Control pressure fairly warm: 3.2 bar (spec says 2.8-3.2 bar NO vacum and 3.4-3.8 bar WITH vacum)
- Control pressure 45 min after stop: 2.8 bar (from 3.2 to 2.8 in 45 min, accumulator is also new)

SO, the reason I couldn't start the car back in september 2020 was fuel pump failure (it only delivered 2.4 bar)

AND, warm start seems to be much easier now, probably due to the new accumulator.

Test drive tomorrow!
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: daantjie on 10 April 2021, 05:09 PM
Nice one  8)!
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: raueda1 on 10 April 2021, 05:26 PM
Nice work!  It's a great feeling when it all comes together you're back on the road.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: UTn_boy on 11 April 2021, 06:47 AM
Took some borescope pictures of the damper cage today (the inside).

It's an old Bischoff 116 470 0516". It's hollow :-)

Pic 1 shows the zylinder wall and the round surface. One piece of metal that is bend. Fairly clean.

Pic 2 shows the opposite side. Two metal pieces are connected. We can see some rust. Confirms that stainless steel can rust, as expected :-)

Pic 3 shows the 14 mm inlet port. Fairly clean.

Pic 4 shows the leak port from accumulator. Full of particles that will go straight into the pump.

I'm considering ultrasonic cleaning. The damper is not that bad, but I have never tried it before, and this might well be an interesting opportunity to test it.


These damper cages are not stainless steel.  They are regular stamped steel, and were painted black when new.  And stainless steel does not rust.  It will stain, it can have deposits grow on the surface of it, but will never rust. 
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 11 April 2021, 11:42 AM
UTn_Boy: interresting that the damper was black when new. All gone now  :)

Are you saying the damper will eventually rust?
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 11 April 2021, 11:54 AM
Great day today!

Tested the system pressure and control pressure during warm-up again. All good!

1. system pressure 5.2 bar (design spec says 5.2-5.8 bar)
2. Control pressure:
- Cold: 1.3 bar (design spec at 10 deg C 0.7-1.1 bar)
- after 10 min: 2.25 bar
- after 20 min: 2.90 bar
- after 30 min: 3.10 bar

Will probably go up to 3.2-3.4 bar when engine is really warm.

Also installed a new fuel hard-line between pressure damper and WUR. A bit tricky but worked out fine.

The car is transformed after the new fuel assembly! Engine starts immediately both cold and warm and idle is very good, although a bit high (approx 850-900 u/min, would love to have 750 u/min). AND, after the test drive today, I believe the car has more power, this is subjective  :)

On to next maintenance item.
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: UTn_boy on 13 April 2021, 12:14 AM
UTn_Boy: interresting that the damper was black when new. All gone now  :)

Are you saying the damper will eventually rust?

If left bare with no paint, then yes, it'll rust just from the moisture in the air.  Since it's already put together maybe brush some paint on it?  Just throwing out an idea. 
Title: Re: K-jetronic pressure testing (troubleshooting)
Post by: Jan S on 13 April 2021, 11:54 AM
Strange .... this damper has been out in the wet for 46 years and no signs of rust (nor paint).