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  #1  
Old 03-11-2018, 05:11 PM
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Join Date: Oct 2017
Posts: 4
Fuel pump noise on 1997 R170 SLK230. Any solutions?

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
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  #2  
Old 03-12-2018, 06:52 PM
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Join Date: Jan 2012
Posts: 5,694
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.
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  #3  
Old 03-12-2018, 07:55 PM
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Join Date: Oct 2017
Posts: 4
Quote:
Originally Posted by 97 SL320 View Post
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.
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  #4  
Old 03-12-2018, 09:38 PM
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Join Date: Oct 2017
Posts: 4
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
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