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1988 560 SL Fuel Pump Whine

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Tim Cleary's picture
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Hello, Can some one please give me some advise on why my fuel pumps whine like a 767 using its hydrallics before takeoff. I receintly replaced them but the whine is still there. Could it be the accumlator? This tends to be embarrassing when folks ask about my car. Please advise.

Thanks :(

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BuyMBparts's picture
Atlanta, GA
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Vehicles
1995 C280
1991 560SEC
1981 380SL
1969 280SEL

What brand are the ones? Bosch is OE and are very quiet, Pierburg is an aftermarket brand and they tend to be on the noisy side even when new.

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Thanks for your quick reponse. I bought the new pumps on e-bay from a place called Quality Performance. The below is how it was listed.

Part number 580 254 911 (bosch)
1985-1998 Mercedes Benz

The price for 2 was $139.00 and the dealer is $600.00. I'm thinking these are aftermarket. I will check with the seller tomorrow, they are closed today. Any other thoughts if they are OEM? The orgional ones made the same whinning noise but with 94K miles.

Thanks

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xrayaz's picture
Peoria, AZ
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2008 S550
2005 E320 Wagon 4MATIC
1988 560SL

I have a 1988 560SL and had both the fuel pump and accumulator replaced 2 months ago and they are silent - I can not really hear them at all.

Michael

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Michael in Arizona (Desert Stars) 1988 560SL in Signal Red, 70,000 miles 2004 E320 4Matic wagon in white, 72,000 miles 2008 S550 in Black, 28,000 miles

nhdoc (not verified)
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nhdoc's picture

IIRC the pump assembly is mounted to the car on 4 rubber bushings...it's possible that the rubber has hardened over time and now makes the body of the car amplify the pump noise much like a drum. I'd get those 4 bushings replaced if the noise bothered me and see if that helps. I suppuse you could test this theory by physically dismounting the pumps and running them but that's probably just as much work as replacing the busings would be. They are cheap parts and could probably be replaced in less than an hour.

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George Murphy's picture
Oak Ridge, TN
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1999 C43 AMG

Tim Cleary wrote:
Hello, Can some one please give me some advise on why my fuel pumps whine like a 767 using its hydrallics before takeoff. I receintly replaced them but the whine is still there. Could it be the accumlator? This tends to be embarrassing when folks ask about my car. Please advise.

Thanks :(

Dirt in the pumps can make them noisy - here's how I clean them:

Remove entire pump assembly (filter, damper, etc,) from the car. Inspect
interior of all hoses for loose debris. If hoses are 100,000 miles old or
more, replace 'em. Take pump off the bracket and gently mount it so pump outlet
is pointing upward.

Attach jumper wires to electrical terminals and note polarity. Have a 12v
battery nearby to use as a power source.

Fill pump outlet with diesel fuel, then jog it electrically IN REVERSE (pump
+ to battery negative; pump - to battery positive) for about one second so
the diesel fuel is expelled from inlet (put a bucket under it). My pump spat
out lots of dirt and crud when I did this - but it ran again! (BIG $$$
saved) I flushed it three times before diesel fuel was clear coming from pump.

Flush pressure damper and other lines on bracket and install a new fuel filter.

CAUTION: DO NOT DO THIS WITH GASOLINE - using the battery and jumper wires
will produce sparks when you connect power to run the pump - with
potentially disastrous consequences if gasoline is used. Use kerosene or
diesel fuel to clean pump...

This procedure resuscitated my stalled expensive FI fuel pump - it's worth a
try...I salvaged pumps from two 280SE4.5s this way also - much to owner's
delight...and they are still working today after many miles.

The FI fuel pumps have very close tolerances inside and it doesn't take much
crud to cause them to lock up - the reverse flush can save you a lot of money...

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Regards,

George Murphy

MBCA Technical Director

865-482-9175

1999 C43 AMG

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mbfan's picture
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there are several reasons/causes why Mercedes fuel pump makes a noise or whine. It can be an indication of excessive pump wear and needs replacement, can be caused by a loose or missing rubber noise insulator around the pump, or physical contact with the bottom of the tank or tank baffles.

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Tim Cleary's picture
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Fuel Flow

Thanks everyone for your suggestions. One more question. Which relay behind the glove box shuts off the fuel flow from the tank? Is there a way to stop the fuel from coming out of the tank ? The fuel line is direct to the fuel pumps..

nhdoc (not verified)
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nhdoc's picture
Re: 1988 560 SL Fuel Pump Whine

The line does feed fuel by gravity. MB recommends clamping it off when disconnecting the line from the pumps for service, IIRC.

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