124 280 E - engine cuts out when foot taken off accelerator

[crossangle]

1995 W124 280 E petrol - 104 engine
This fault started suddenly without warning from standing overnight after having worked perfectly the day before.
Started engine and engine fired up fine - auto choke did not appear to have cut in but that happens from time to time and I can compensate with foot acceleration. Started again and held the engine revs on the accelerator and everything fine until I took foot off accelerator - engine cut out . Started up again - same thing.
Started engine again and held revs at 1000 and above until engine warmed up . Took foot off accelerator - engine stopped.
As stated did not hear the normal fuel pump activation on switching ignition on prior to starting engine.
Could this be a fuel pump/OVP relay problem ? Cannot understand why engine functions/runs normally providing I do not take my foot off the accelerator.
Have checked relays behind main fuse box and behind battery - and those with external fuses seem to have fuses intact.
Any guidance would be appreciated

 

[DREAMER NO2]

Look for vacuum leaks . Also that the micro switch on the throttle assembly is clicking on and off . Also the linkage to the throttle will have a bush in there check any free play .The bushes ware out letting the cable loose this lowers the revs get this free manual google for this Model 124 Maintenance Manual Index Also the oil filler cap must be air tight .As well as the fuel tank filler cap seal .

 

[crossangle]

Look for vacuum leaks . Also that the micro switch on the throttle assembly is clicking on and off . Also the linkage to the throttle will have a bush in there check any free play .The bushes ware out letting the cable loose this lowers the revs get this free manual google for this Model 124 Maintenance Manual Index Also the oil filler cap must be air tight .As well as the fuel tank filler cap seal .

 

[crossangle]

many thanks Dreamer No 2 - much appreciate your reply
Will have a look at your suggested items - where will I find the throttle assembly micro switch - will that be on the throttle linkage assembly in engine compartment ?
I take it you do not feel the relays are the culprit ?
Have tried Google for manual; but page coming up "unavailable"
Again many thanks

 

[DREAMER NO2]

Cossangle are you in the UK .. I just checked the free manual and its working for me just tried it . The micro switch is on the throttle linkage in engine compartment . Might be the lambda sensor in silencer .

 

[DREAMER NO2]

You can sort this out fast with a code reader that plugs in to the obd port under the dash .

 

[crossangle]

Hi Dreamer No 2 - thanks for your info - much appreciated
Yes I am in the UK - Can you give me the link to the website please - cjross.angle@btopenworld.com
Do not appear to have an OPD connection under dash (driver or passenger side) - have not dismantled the black plastic coverings though - I seem to have the attached socket (picture) in engine compartment near servo -Vehicle 1995 124 E280 engine 104

 

[crossangle]

p.s. I can now hear the fuel pump buzz/activate when turning ignition on before starting !!!!

 

[DREAMER NO2]

Looks like you have the early type diagnostic socket . You need to know just how to check the blink codes ,.

 

[DREAMER NO2]

Try this google- Mercedes Gen- in dont forget the - then inn search on the right hand side put BLINK CODE W124

 

[crossangle]

Hi Dreamer No 2
Many thanks for info - fascinating website ! - now have the codes for the 16 pin diagnostic

 

[DREAMER NO2]

crossangle did you find time to check the bushes in the throttle linkage ?. if one is missing the revs will fall .Just hold the cable and see what play you have should be around 1/8 inch mind you check the throttle cable only.

 

[crossangle]

Hi Dreamer No 2
No have not yet fully addressed all the items So far I have been going at it piece-meal with no continuity and am planning to have a real go at everything this weekend. Will check all the items you mention and also try and get a reading from the diagnostic. Presently am intending to also have a look at the automatic choke - when I start the engine cold the auto choke does not cut in at all now - whereas before - more often than not it did. I know that even when I run the engine on the accelerator up to normal op temp the problem exists but at 1000 revs the engine will maintain running (without accelerator) albeit a bit lumpy from time to time - so wonder if there is an associated problem there.
Will do the easy bits first.... throttle link bushes, vacuum leaks etc.,
I really do appreciate your info - it is all very valuable and I now have a printed out book with all the blink codes for the my 124 model and year. So if the diagnostic system works properly it should help considerably.

 

[DREAMER NO2]

Did i send you info on how to obtain the free manual ?

 

[crossangle]

No - but would appreciate the link - many thanks

 

[DREAMER NO2]

Check your cold start valve . Use a large screw driver and place it on the top of the valve and put your ear on the screw driver you should hear it click when someone turns the key to start . The other part i would remove and clean out with white spirits is the ACV valve see picture .First is cold start valve or some call 7 injector .Second is ACV valve . These parts on the engine are the same as yours only the engine is a 300E but the ACV is the same .

 

[crossangle]

Thanks for info will try these fixes ......... as of today we have heavy rain and it is giving it for a couple of days - so will be delayed somewhat. Why don't these things happen in dry weather?? !!!!

 

[DREAMER NO2]

Crossangle Weather is getting bad in the UK right now .Winter is on the way .I removed everything from my car yesterday all but the battery . I wipe the car off everytime it rains, and the day before last did it 6 times ..lol I will get the car cover down from the loft asap along with the thermal sheets that go on the car before the cover just to give it a little more protection from frost and snow ,thats if we see any snow this winter. And i pack the engine compartment with 2 old quilts to stop the cold .She [the car ] get more love than the war depot [wife] lol...

 

[crossangle]

Hi Dreamer No.2
Thanks for your last missive - progress to date - replaced OVP (on off chance) - to no avail.
My understanding of 104 280 E is that cold start idle & idle speed generally is controlled by the ECU through the throttle body. On a cursory look ( through sheets of rain !) at engine compartment cannot see a cold start valve or ACV as per your photo.
Am on hold at the moment considering next step. Will probably dismantle down to and remove throttle body - cleaning reservoir valve on the way !
Am also considering whether to contact local Merc Dealer to see if they could "override/convert" 16 pin diagnostic plug to give a more focussed diagnosis.
As far as I know the wiring loom has been replaced (as advised by the vendor to me 2 years ago .......) so am assuming I do not have wiring gremlins.
At the moment, as a temporary measure, I have inserted a spacer at the base of the throttle cable to increase the idle/at rest speed to enable the car to be driven. Not sure whether this will have an adverse or no effect on the engine management via the ECU.
Weather continues to be against me !! ( better than Japan though !)

 

[brianbrian]

Timing chain could have jumped a link