Who knows how to advise me: my 1994 E420 ran absolutely reliably until July 2017 when I encountered a stalling engine after sputtering and hesitation. The car broke down twice during the last 3 weeks. My mechanic diagnosed it as a faulty fuel pump (actually there would be 2 of them in this model which were the original ones). After that exchanged, I encountered the same issues: car would start up well, run for a long time without problems, but occasionally one would feel an interruption of power (perhaps 5 sec. long), or the engine would almost die when being in congested traffic. I also noticed that the RPM would drop almost to 0 when revving the engine (it usually recovers to normal idling, set to ca. 500-600RPM).

My mechanic now exchanged the distributer cap and rotor, a replacement I had done a year ago (!), and "cleaned" the injection nozzles. I am not sure whether the problems are resolved, and I am not planning to use the car for long distance trips.

A Mercedes Benz dealer near me on Long Island is not able to help as the car is too old (I guess their mechanics are not trained to trace problems, but rather analyze everything through the newest computer software!
Does any of you know an expert shop specializing in older Mercedes on Long Island (or near NYC) which is thoroughly familiar with those (common) issues? Thanks for your replies!

 

Did your mechanics check the gas tank internal rusts, fuel lines and filters ? I recommend that if not done. I had mine done recently and there were rusts within the tank.

Good luck with the resolvement.

w/ smiles
Jimmy

 

Have you sorted the problem? It could be interruption of fuel supply as Jimmy suggested. It could also be caused by electrical issues like a failing fuel pump relay (in the engine compartment), clogged injectors, a dying fuel pressure regulation, or faulty MAF, or even a dying ECU. Would suggest you go back to the workshop which replaced your fuel pump to re-assess the possible causes, but let him convince you or seek a second opinion before agreeing with the repair.

 

I had a 1994 W124 E420 until last year.
The first thing you have to do is to research and find the list of codes for this car.


The second thing to do is to build yourself a code display unit.
This is a very fancy name for s string of LED soldered in series.


Then, the 1994 W124 has a weird code setup. Prior to 1994 only California models had a OBD1 system, this consists of a pushbutton system located in the engine compartment on the passenger side by the strut tower. You push that button and there is an adjacent LED that blinks. The number of blinks tells you the code.


However, this system could only read one "chapter" of codes, was handy in day by day situations.


More advanced problems require the LED string.


I traded my W124 and still have the LED, PM me and I will find a way to give it to you, I don't live far.


The E420 suffered from two problems:
1 The top engine harness has to be changed because the insulation is eco friendly and designed to degrade after 15 years, by now they all flake off. However around 2000 replacements were made and installed by Delphi, a OEM supplier. There are at any given time some on ebay for sale.
The dealer will sell you one for $700.


if this went bad you may get some sort of limp mode.


The other problem is with the Mass air meter, the big funnel in the center top of the engine.
That has an electronic unit that can have internal problems.
This is more tricky as the new price is more than $700 I think and because there was a rebuilder that was in business till something like 2012, not sure if he is still now.
You can try to find a used module.
Replacing it is also a bit tricky.


The problem with that is that there had been a nice write up about it, but with the Photobucket disaster (where Photobucket is trying to squeeze money out of car enthusiasts by locking their photos), the pictures of this pictorial may not show anymore since couple months ago.


Anyway, once you read the code, this will point you in the right direction.


Start your research here:


http://www.w124performance.com/

 

Vladds- I have a "California" '92 400E. Can you expand a bit on how to construct the LED string for this model? It seems you are saying it's possible I may need one one day... or not if I'm lucky I suppose. The car is new to me, I've only had it couple of weeks but I happen to drift across this thread and thought why not ask about it.

Also, do you know if the '92 400E has the same Mass Air complications or not? It's the same M119 engine correct? Thankfully, my car has the Delphi harness upgrade. Thanks in advance!

 

It's just a LED with two terminals soldered, so you can insert in the pin holes of the big round terminal.
I had in my toolbox a bunch of LED bought from Radio Shack. Could not tell specs. So I tried one, it got hot lit very strong then out. So I tried 3 in series soldered together, they lit but seem to want to burn off. By the time I soldered 8 in series, it seemed it's going to last. That's all.