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  #1  
Old 04-07-2004, 07:18 AM
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Noisy Fuel Pump? R129 500SL

Hi all

Last week I had an odd incident where after an hour or so of motorway driving I stoped for an hour. Then she wouldn't restart. As the ignition was turned on to just before the start position I heard a weird gurgling/rumbling sound (very difficult to explain) coming from the rear of the car and I'm sure I didn't hear the normal tinkling of the injection pump.

Several start attempts and still nothing, or at the very most the occasional fire. The solution was to depress the pedal just after start and finally she started.

I then drove for a further 45 minutes and exactly the same symptoms persisted ie, she failed to restart but no gurgling sound but I'm sure that the injection pump when running was loader than normal!

I filled the tank up to full where it had been previous around the 1/4 mark (which it has never been before) and all is now well again.

Would an airlock in the fuel system cause these symptoms? Is the fuel pump on the last leg? Are there any simple tests as a user I can perform?

Any thoughts or suggestions most welcome.

Lea

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'89 190E 2.6 - sold in 2002

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  #2  
Old 04-07-2004, 12:04 PM
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Location: Dallas/Fort-Worth
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MB (Bosch) fuel pumps should hiss when normal...a buzzing pump indicates impending failure.

It is also the sound of a fuel-starved pump (usually more of a growl instead of a buzz). My electric pump on my VW does this when I first start the motor, then quiets down after the fuel pressure goes nominal.

If this is the case, then this may be a fuel pressure issue caused by something other than the pump...the pump may just be echoing the woes...
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  #3  
Old 04-07-2004, 03:01 PM
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Thanks for the reply.

Yes, a growl is the exact adjective I was looking for as this is what I heard.

Fuel starvation is what I reckon too as it ties in with 1/4 full and that I've never run the car that low, and, that the engine was quite hot and perhaps suffering from an air lock? - but where to start?

Next weekend I'll fit a new fuel filter (just in case) but if you have any further thoughts then please let me know.



Cheers
Lea
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'89 190E 2.6 - sold in 2002

http://antron.pwp.blueyonder.co.uk/i...nature/Sig.jpg
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  #4  
Old 04-07-2004, 03:17 PM
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Try running the air conditioning. There might be a fuel cooler and the pump may be temperature sensative. Thats what mine did.
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  #5  
Old 04-07-2004, 05:10 PM
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Uhm, that's also very interesting as I didn't run the AC for most the trip as it wasn't warranted.

Does anyone know if LH systems suffer with airlocks causing fuel starvation or am I barking up the wrong tree here?

Cheers

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http://antron.pwp.blueyonder.co.uk/i...nature/Sig.jpg
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