Hello

Does anyone know of a solution to this problem? I see it mentioned often but never any resolutions in the forums.

I have this drohning / humming/ buzzing noise from behind the right seat when the pump runs for 2sec and when the engine runs. It is seriously annoying and I will have to sell this car if I cannot solve it.

The noise is also strong from the tank filler. I open that and listen there, I can hear it loudly from there.


It is fuel pump noise for sure and it transmits itself into the tank which then spreads and amplifies it throughout the rear wall of the passenger cabin.


1) I changed the filter.
2) I changed all the hoses going from the pump to the filter to the coal cannister etc.
3) I ran the pump with it's whole cradle removed and hanging loose under the car. No change.

I have NOT changed the hose from the tank to the pump. It looks good but is not super-soft.

I now changed the fuel pump itself as well.

And it is much worse! This pump is even louder.


Any suggestions will be greatly appreciated as I do not know what to try next and I am sure this car did not leave the factory like that.

Regards
Bernt

Things I'd check.

In tank strainer, if this is clogged, the pump will cavitate.

Check fuel pressure. If the return line is crimped, the pump will be straining against it's internal over pressure relief. If this has occurred, I'd expect the motor to go rich and trip a code though.

Does this have a " drive shaft through the fuel tank " like the W202 your car is based on? If so, these use a venturi pump to get fuel from left of tank to right where strainer is.

If there is a pulsation damper anywhere on the pressure side of the pump, a failed one may cause this noise. The damper might even be at the engine or on the fuel injector rail. It will probably look like a fuel pressure regulator if it has one.

In any event, I'd be tempted to run the pump manually then poke around the engine to see if the noise is coming from the fuel pressure regulator.

Thanks.
I have done all that and more since I am battling here since 2015 with this rubbish.

There is no damper andit is not a split tank like W202.
It is not the regulator at the engine and the source is the pump transmitting the noise back into the fuel tank via the 15mm (unobtainium) thick hose from the pump into the tank. The whole tank then amplifies this back into the rear wall of the cockpit.

The fuel pressure is correct and I checked it just after replacing this pump again last week.

The only thing I have not done is change that (15mm) hose. It could be too hard and transmit the vibrations but I have no new one to compare to and they want $125 for a new one here!


The darn noise changes with voltage changes like when the indicator is on or when the brake lights are on.

I did read somewhere in the Mercedes WIS from around before 2004 that when fuel pump noises persist, an additional damper can be fitted AFTER the pump.

I was not able to find any info on said damper. They showed a picture of it but no part number. Looked like a little can.

Does anyone know more about this perhaps?

Regards
Bernt

Hi Bernt, I can't help you with your damper question, but instead I have the same problem as you.

Same annoying noise, tried almost everything as you did. No luck at all.

So, I rise my question: Did you finally fix it?

Hope so, thank you in advance.

I did fix it as below:
That fuel pump eventually just died due to some tiny rust bits seizing it. I replaced it and it was the same/worse. I then returned the new pump and purchased a Pierburg pump (same as Mercedes used) instead. All the vibrations are gone and I cannot even tell the pump is running from inside the car.

I opened the old pump and found that the 2 archimedes screws had corroded/worn through their hard chrome surfaces and a had a slightly rough surface.
The first replacement pump then used a different pumping method with an impellor. It looked identical from the outside! but was a LOT more noisy than the old one. I returned it. The Pierburg pump uses the same archimedes screw type method as the original and it really is great.

So my solution was in the end to replace the pump with a new one from Pierburg. I replaced nothing else at that stage and the noise was gone.

Hi fellows, I went to the "Pierburg" solution as Berntd did.

No more noises, there's a huge difference in terms of quality.

Happy driver again, thanks to OP.



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