Author Topic: K-jetronic pressure testing (troubleshooting)  (Read 4267 times)

Jan S

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #45 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  :-\
1975-mod W116 450 SE with 6.9 engine

daantjie

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #46 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.
Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #47 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).
1975-mod W116 450 SE with 6.9 engine

raueda1

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #48 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.
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

TNNBENZ

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #49 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 ???

Jan S

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #50 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.
1975-mod W116 450 SE with 6.9 engine

raueda1

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #51 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.
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

TNNBENZ

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #52 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...
« Last Edit: 25 November 2020, 05:07 PM by TNNBENZ »

TNNBENZ

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #53 on: 25 November 2020, 05:02 PM »
Raueda1, is your great photo similar to a 4.5L engine ?

raueda1

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #54 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.
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

raueda1

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #55 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?
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Jan S

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #56 on: 26 November 2020, 10:50 AM »
raueda1; thanks for this safety advice. Another item on my to-do list.
1975-mod W116 450 SE with 6.9 engine

Jan S

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #57 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.
1975-mod W116 450 SE with 6.9 engine

raueda1

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #58 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/ .  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,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Jan S

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Re: K-jetronic pressure testing (troubleshooting)
« Reply #59 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.
1975-mod W116 450 SE with 6.9 engine