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Discussion Starter #1
Hello,
I am having truouble with my fuel pump. It making a load noice. I replace it already twice with an original BOSH pump.on the lates one i test it on a fuel pumo bench and there was no noise coming from it, but once i install it the noise was there. I really do not no know what to do any more, if some one can direct me much apreciated it.
 

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Discussion Starter #3
This is a 1984 the pump,the filter, and the fuel accomulater are new but the noise ia a hum noise
 

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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
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1,389 Posts
As Brad mentioned it might not be fitted correctly, or alternatively there's restrictions in the fuel tank /hoses that are straining the pump to create a flow and sustain working pressure. Might be an idea to record a clip, stick on YouTube and share the link.
 

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Discussion Starter #5
I will record it and place it on youtube. I have several pump that are bosh. The first pump was noise free for a few days. After a few days the noise came back. And the second one leak,plus noise now the 3rd one making noise and it a more powerful pump
 

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1998 ML320, 1975 280C
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45 Posts
I would also look at the mount rubber for the pump system. Ifyou have metal on metal, all the noise will go through the body, and probably be amplified as it vibrates the floor pan.
 

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Discussion Starter #7
The rubber they are new. I need to check if the flow of gas is flowing with out restriction, how do i do that?. Also when i check the pump on the fuel pump bench they don't make any humming noise and the flow is very good, any subsections
 

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1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,258 Posts
You may have a partial blockage between the tank and the pump due to rust or other crud in the tank.
 

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1984 380SL
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2,301 Posts
Yeah, keep running Techron through it, change the filter again and again. This worked for me. The hum is cavitation, bubbles developing because of the strain.
 

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1989 R107 560SL
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101 Posts
Chiqui311 As you have the same problem with numerous pumps and a new filter and accumulator and the pump runs fine on the bench (I assume you use a small fuel cell as opposed to the car's tank) it would point to a restriction or problem at tank side, whine being pump struggling to draw fuel ? On my car (89 560sl) there is a strainer in the base of tank. You could try removing this (if you have one on your 380sl) or maybe remove whole tank. I recently did this and wasn't difficult at all. An old car could well have a lot of crud in the tank or at strainer. Best of luck.👍
 

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Discussion Starter #12
Ricci, im planing on changing the stariner to see if this take care if the problem. Once you change your stariner did the problem when away?
 

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1989 R107 560SL
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101 Posts
Chiqui, I had a fuel (dual on 560) pump failure then a fuel pump relay failure, I haven't had the car long and so renewed the pumps, accumulator, fuel filter, and numerous other parts that were failing or just old in an effort to just troubleshoot future problems. A look inside the fuel tank (and it's also an easier way to change strainer) was something I was keen to do, particularly as it's not a difficult job. Actually my tank was clean as was the strainer, I personally think it was removed and cleaned prior to me purchasing the car as there were 4 bolts missing from the bulkhead and it was hard to see how a 30 year old car could have such a clean tank. Finally when I used to fill the tank it would take a full 5 minutes to fully register the level on the gauge, so I removed this while the tank was out (there's a very interesting article on this on here) gave it a little clean up and hey presto gauge registers immediately now. So really in answer to your question I never really had a problem caused by a dirty tank and so it never went away but I am happy now knowing tank is clean with a new strainer and gauge works well. I am no mechanic and not very experienced but have to wonder why you have gone through so many pumps and they whine when drawing fuel from your tank, blockage ? blocked strainer ? crud in tank ?
 
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