Helping a friends with their 1988 W124 300E No start after driving.

Symptoms indicated that the fuel accumulator was failing. So we purchased a new accumulator from Pelican Parts along with various hoses and fuel filter etc.

On the day of the repair we removed the fuel line from the dry side of the accumulator and we’re preparing to drain the fuel from the tank and then remove the fuel pumps, filter, accumulator etc. and rebuild the system but we were missing a few seals for the banjo bolts so we decided to button it back up and gather more parts before proceeding. This would have the additional benefit of running fuel out of the tank.

Now the car seems to be fixed. Starts and runs like a champ. Idles and runs better than it has been for years.
Why?

What did you remove? What were the symptoms? What did you test prior to coming to your conclusion? Was the CEL illuminated?

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1990 190E 3.0L

The fuel accumulator is an often overlooked component, but it can be changed without draining the fuel tank.

If you want the details including a simple on-the-car test and a FA destructive failure analysis, search for thread started by me, Duke2.6. There aren't many.

You can use a vacuum pump to determine if the removed FA is actually defective.

If you can ultimately find the cause of the problem and what caused it to be fixed, let us know. These cars are fairly complicated and sometimes problems can be solved, but we don't know what the actual solution was.

Let is know!

Duke

The first thing that I did on the day was to remove the “dry side” fuel hose that returns to the main fuel hose. I expected that there would be a bit of fuel to leak from the accumulator but was surprised that the hose was free flowing from the hose.
I have only had experience with the 6.9 that has a check on that line. It appears that the line on the 300E just Tees into the main fuel line. (Part no longer available)
There is signs of leaks from the banjo bolts so I attempted to tighten the 17mm fittings with a lot of pressure and it didnt seem to budge.
As I said before, I decided to button it back up and get the copper seals to replace and properly rebuild the system. Now however the car runs like new.

I am interested in the vacuum test.

[QUOTE=Duke2.6;4305103]The fuel accumulator is an often overlooked component, but it can be changed without draining the fuel tank.

If you want the details including a simple on-the-car test and a FA destructive failure analysis, search for thread started by me, Duke2.6. There aren't many.

You can use a vacuum pump to determine if the removed FA is actually defective.

I read what you said about using a Mighty Vac to check the Fuel Accumulator

Do not understand why it requires vacuum to perform the test? It seems that fuel entered the clear tube when the car was cranked.

Does there need to be vacuum of will a clear tube alone work?

This is what I said in a 4-23-2015 post in the following thread:

http://www.peachparts.com/shopforum/tech-help/365488-m103-starting-problem.html


Additional analysis and discussion with some knowledgeable CIS guys pointed to the fuel accumulator, which can easily be tested on the car by disconnecting/plugging the hose from the backside that tees back into the supply line hose from the tank and installing a clear vinyl test hose to the nipple.

Upon turning the ignition key on, which energizes the fuel pumps for about a second, fuel filled up the test hose. The accumulator was obviously leaking internally, so the system was not holding operating pressure after shutdown, and the leak made it hard for the fuel pumps to develop operating pressure during cranking, which is why it became hard to start, hot or cold.


In another post I said that I tested the fuel pressure regulator vent nipple with a vacuum pump and it held vacuum indicating he FPR is okay.

Fuel leaking from the "backside" of the fuel accumulator when the ignition is energized (on the car test) indicates the internal diaphragm is ruptured, and this can be verified by a vacuum pump test once the accumulator is removed.

Duke

Thank you for clearing that up.

It took a long time to find your past comments and I didnt get all of it.

New accumulator and filter installed and now the pumps do not run.

The car cranks but will not start. The usual fuel pumps short run to get the pressure built up before crank doesn’t happen.

Any Ideas why?

Is there a fuse for the fuel pumps?

If the fuel pumps don't energize for about one second when you turn on the ignition, the fuel pump relay is suspect. Look at the following thread.

https://www.peachparts.com/shopforum/tech-help/418715-crank-but-no-start-88-190e-2-6-a.html

Duke

I used a power probe on the fuel pumps and they run and I knew that there was a relay but didnt know where it was located or the pin trick. Great information.

I was also skeptical of the URO part so it was interesting to see them reply.

I will order another round of parts from Pelican and report back.

Another question is; when the key is turned to run and start is there supposed to be a buzzer going? I have a few Mercedes and none of them do that unless a door is open. I am not familiar with this model car but the buzzer is very loud and it seems wrong to me but the owner says its normal.

IIRC Pelican announced that beginning 1/1/2023 they are offering a lifetime warranty on parts. I bought my fuel pump relay in late December '22 so mine is not covered under this new policy, but yours should be.

As far as the buzzer is concerned, I think it just sounds if you open the door with the key in the ignition switch. This rarely happens with me since it's SOP for me to not insert the key into the ignition switch prior to closing the door upon entry and to remove the key before opening the door upon exiting.

There's also a buzzer if you leave the lights on, but I forgot if it sounds if you leave the lights on after shutting down the engine or upon removing the key.

I guess after over 35 years of ownership operation is so routine that I can't remember all the details.

Duke

Thanks for the warranty information.

The buzzing is terrible to me as I do the same. Close the door turn the key. When the key is turned in this W124 is buzzes so loud that there is no way to hear if the pumps spin up and by the time the buzzing stops the cycle is complete.

The saga continues…
Performed the procedure to check the FPR by removing it and jumping the #7 and 8 sockets. The pumps ran so I ordered a new aftermarket relay from Pelican, installed it on the car, the pumps run but no start.

The car ran great before draining the tank and replacing the fuel filter and accumulator and now the FPR. We thought that it may have lost prime when the fuel tank was drained.

Any advice for my next step when I get back to the car?

Did you try jumping the relay and running the car while pumps are running? Did you test if fuel was making it to injectors?

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1990 190E 3.0L