Author Topic: Engine problems  (Read 309 times)

mercw116

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Engine problems
« on: 23 February 2019, 01:26 PM »
Hi, I recently bought a 1980 w116 350se k Jetronic which was a non runner when I got it (been off the road around 7 years) I put a fully charged battery on it and some fresh fuel, but it would not start, I then put some fuel directly down the intake and it started up, but would not rev, once the engine was warmed up it idles good and will rev if I press the accelerator slowly, if I try to rev it at normal speed, it will rev fine up to about 1500rpm and then will start to cough and splutter. When the engine is warm it idles good and can be turned off and will  start again instantly while its warm. I am thinking its maybe fuel starvation? or a air leak?  and I know there must be a problem with the choke, if there was a problem with the warm up regulator would that cause the symptoms i'm describing? or does the WUR only effect the start up? any help will be much appreciated.

djenka018

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Re: Engine problems
« Reply #1 on: 23 February 2019, 03:37 PM »
after 7 years problem could be everywhere but warm running being good is a positive sign.
No choke, WUR will add more fuel for up to 4 minutes for a cold start (outside temp dependent) and Cold Start valve will assist for a few seconds in total, whilst cranking with temp below 15*C
WUR also sets the fuel to rpm AFR slope through control pressure at warm and assists in WOT enrichment (vacuum goes below threshold and WUR enriches the AFR)
If you can start it but cannot maintain the run until warm it can be rich (black smoke), lean (obnoxious smell, maybe) or it can be poor ignition and/or ignition timing.
I'd start with replacing cam oiler pipe plastic fittings and cleaning the oiler nozzles, inspecting the timing chain and guides at the same time, followed by replacing all the injector and sleeve seals, even sleeves if cracked.Next is to check for other vacuum leaks and address leaks.Ignition can be checked by confirming 4-5V on one side and 0.5-1V on the other side the coil bobbin terminals with ignition on and engine not running. Timing is usually 0deg at warm idle.
After that, check the System and WUR fuel pressure for the specs for the engine variant you have.Did I mention spark plugs? Replace or clean with the carby cleaner, wire brush and re-gap.
This is common knowledge and a starting point.If you're lucky, the fault will be within above.Vacuum leaks all over and WUR pressures are common culprits.Adjusting the CO screw should be the very last thing done.
Origin of the car and your location can help the tuning of the response to the engine variant you have
Vitamin C for SL... the SLC

Diesel 617

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Re: Engine problems
« Reply #2 on: 23 February 2019, 07:08 PM »
You can save you self some hassle by going to the fuel source. Remove the first aid kit and remove the fuel sender underneath and have a good look in that tank, sounds like it could be varnish. You issues sound like my issue. Can runs great when the fuel system is bypassed and starting fluid or fuel goes through the intake. The socket is a size 46mm or 1 13/16th. If there in any varnish in you tank, your fuel distributor is probably clogged (the port sizes are in the micro millieters, think grain of sand, where fuel has to go through) and warm up regulator seals are probably shot, and clogged as well.

If you issue is indeed varnish, (black stuff, anything but whistle clean) drain all the fuel. have the tank professionally cleaned, replace all the hose and lines around the fuel tank, new fuel filter, accumulator would be a good idea. All new hoses connecting the accumulator, pump and filter.
In the engine bay, pull of the Fuel distributor and Warm up regulator, and the injectors send them in to cisflowtech in fairhope, AL. Excellent work and the exact right people to send you parts to.
Clean that vanish out of the lines. Buy two new fuel filters. Hook one up in the engine bay (fuel feed and return lines together, and get two cans of carb cleaner and empty them in a a clean bucket put the feed and return lines from the fuel pump into the bucket and power the fuel pump to flush the lines of all the varnish. Run it for about an hour

1980 300SD
2 OM617.950 complete with transmissions
1980 450SEL Transmission (for sale 150kmi 100$ + freight)

In my imaginary garage
European 1974-76 450SEL 6.9 Green Velour

mercw116

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Re: Engine problems
« Reply #3 on: 24 February 2019, 11:26 AM »
Thanks guys that gives me plenty of things to go at. I am in the united kingdom and it has the 3.5L engine. When I bought the car the seller said it was running, but when the recovery guy collected and asked to start the car, the seller said it was out of fuel!! when I got it home I removed the fuel cap to gauge the condition of the fuel, but it didn't smell bad, so I put a couple of gallons in just to try and get it started. A few days later I fitted the dash gauges(as they had been removed to fit a new ignition barrel) and when I connected it up the fuel registered half a tank, so there must have been a good bit of fuel in it when I got it. Regarding the fuel distributor, is it possible to put one in a ultrasonic cleaner as a complete unit? or is that a bad idea? as it sounds like its a lucky dip if they work again after being disassembled.

Diesel 617

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Re: Engine problems
« Reply #4 on: 25 February 2019, 07:16 AM »
Regarding the fuel distributor, is it possible to put one in a ultrasonic cleaner as a complete unit? or is that a bad idea? as it sounds like its a lucky dip if they work again after being disassembled.

Quote
your fuel distributor is probably clogged (the port sizes are in the micro millieters, think grain of sand, where fuel has to go through)
The whole unite must be disassembled, as the orings as almost guaranteed to be dry rotted and could also be falling apart leaving debris in the unit, along with gasket material and what ever else snuck it was through the fuel lines over the decades. When I had the opportunity to see  one of these units apart for cleaning, the slots where the fuel had to go through was sliver thin to the point where the naked eye could only see the opening with a flashlight underneath the piece. It was less than 0.5mm.

Give the gas tank a check inside and report back from there. If there is any varnish in the tank, cleaning up and fixing anything in teh engine bay will be all to waste as the vanish breaks off and plugs the system again, requiring another complete fuel system refurb.
1980 300SD
2 OM617.950 complete with transmissions
1980 450SEL Transmission (for sale 150kmi 100$ + freight)

In my imaginary garage
European 1974-76 450SEL 6.9 Green Velour

mercw116

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Re: Engine problems
« Reply #5 on: 04 March 2019, 11:46 AM »
Bit of a update, I decided to drain the fuel from the tank and it was brown!! I then got a couple of gallon of fresh fuel and some fuel injector cleaner and put that in the tank and run the engine for around a half hour, with no noticeable change. I just did the same again today and I noticed that about 10 seconds before the fuel run out, the engine would actually rev up nice and smooth. Now this has me thinking, did the injector cleaner work? or could it be a sign that the fuel pressure is high?

daantjie

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Re: Engine problems
« Reply #6 on: 04 March 2019, 01:12 PM »
Bit of a update, I decided to drain the fuel from the tank and it was brown!! I then got a couple of gallon of fresh fuel and some fuel injector cleaner and put that in the tank and run the engine for around a half hour, with no noticeable change. I just did the same again today and I noticed that about 10 seconds before the fuel run out, the engine would actually rev up nice and smooth. Now this has me thinking, did the injector cleaner work? or could it be a sign that the fuel pressure is high?

Well if a little is good, then more must be better, right 8)!?  You can always pull the injectors and bench test them for flow/spray pattern if you have the right setup.  K Jet injectors are cheap (relatively speaking of course) so you could just replace them all.
There is a mesh type filter in the intake pipe connection on the fuel distributor, this might be clogged with crud.  Release the fitting (carefully, use line wrench with counter hold) and check the connector  when you crack the line, here you will also see the quality of the fuel dribbling out of the fuel distributor.  You can also crack the return line on the fuel distributor and see if you are getting return flow out, and again the quality of the fuel coming out.
One more spot to check is the hard line connections on the Warm Up Regulator  There is also a fine mesh filter/screen here which could be crudded up.
Daniel
1977 450 SEL 6.9 - Astralsilber

mercw116

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Re: Engine problems
« Reply #7 on: 04 March 2019, 02:38 PM »

[/quote]
Well if a little is good, then more must be better, right 8)!? 
[/quote]  Yes one would think, but doesn't a higher fuel pressure mean less fuel gets through the fuel distributor? correct me if i am wrong, as i am new to the k jet workings. My thinking was that the fuel would have been aerated as it got down to the last dregs of fuel and this may have caused a drop in the pressure? hence why the engine revved so nicely for about 10 seconds before it ran out of fuel. Also I did check the filter at the fuel distributor and it did not have any bits in it. I will have to check the filter on the WUR as i didn't know about that one.

djenka018

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Re: Engine problems
« Reply #8 on: 05 March 2019, 04:22 AM »
Quote
Yes one would think, but doesn't a higher fuel pressure mean less fuel gets through the fuel distributor?
I believe so.In due time I will empirically confirm that, from what I understand the K-Jet - lower fuel pressure makes lesser counter balance to WUR control pressure thus allowing more fuel.
But we're talking here small differences which make lean or rich condition, not a "no run" condition.
The best method is to go scientific and plug in one of these inexpensive WUR control pressure meter and see where you're at.
Fuel injector works slowly and it may take months. In my experience it works faster if it is concentrated but then you must have frequent short engine runs to full warm up followed by a few hours or overnight pause for fresh solvent/cleaner to enter FI components.Some great help can also come from carby cleaner down the throttle at WOT until it chokes and stops, wait 5 min then rinse and repeat
I recently revived my car from a long dormant period (seized fuel pump) and noticeable change attributable to fuel injector cleaner is only showing after approx 25L of fuel  plus 300ml cleaner burnt through ~1hr long idle runs and temp reaching ~100°C.. then rest the engine for a day rinse and repeat.
I believe systematic approach will give you quicker results.Long dormant periods will seldom have a silver bullet solution (unlike sudden faults) because a number of things line up causing near faulty or faulty state.
Vitamin C for SL... the SLC

raueda1

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Re: Engine problems
« Reply #9 on: 05 March 2019, 08:28 AM »

Well if a little is good, then more must be better, right 8)!? 
[/quote]  Yes one would think, but doesn't a higher fuel pressure mean less fuel gets through the fuel distributor? correct me if i am wrong, as i am new to the k jet workings. My thinking was that the fuel would have been aerated as it got down to the last dregs of fuel and this may have caused a drop in the pressure? hence why the engine revved so nicely for about 10 seconds before it ran out of fuel. Also I did check the filter at the fuel distributor and it did not have any bits in it. I will have to check the filter on the WUR as i didn't know about that one.
[/quote]I went through similar issues.  I'd strongly suggest biting the bullet and adopting a comprehensive approach:  Check all those little sieves, deal with tank, replace filter and then test it all.  It's really not that hard.  There's an excellent Bosch K-jet diagnostic document somplace that steps through the whole process from start to finish - how to test fuel flow, pressure, etc etc.  I ended up cleaning tank, replacing sieve, replacing rubber hoses on fuel return and replacing a bunch of other stuff (pressure regulator, pressure accumulator etc).  Thing is, it ALL needs to be right or you'll end up chasing your tail.
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

mercw116

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Re: Engine problems
« Reply #10 on: 05 March 2019, 11:08 AM »

[/quote]  I'd strongly suggest biting the bullet and adopting a comprehensive approach:  Check all those little sieves, deal with tank, replace filter and then test it all.  It's really not that hard.  There's an excellent Bosch K-jet diagnostic document somplace that steps through the whole process from start to finish - how to test fuel flow, pressure, etc etc.  I ended up cleaning tank, replacing sieve, replacing rubber hoses on fuel return and replacing a bunch of other stuff (pressure regulator, pressure accumulator etc).  Thing is, it ALL needs to be right or you'll end up chasing your tail.
[/quote]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          Your right, I need to start going through everything properly, but to be honest I don't really have the time it needs at the moment and was hoping I might get lucky with an easy fix! I have made a shopping list of all the service items like filters,hoses,etc… which will need doing anyway, so will start from there.