Fuel Pump - Fuel Pump Noise 300SL

[Paul Woodman]

Having recently purchased a 1987 300SL W107, I have noticed that I can hear the buzz of the fuel pump running when I am stationary with the engine idling. I can also hear it if standing outside at the rear of the car.

Is this just a normal characteristic or is it a problem ?

If it is a problem, what is involved in replacing the pump.

The pump runs continuously all the time engine is running, but I assume this is normal and it is pumping around a loop circuit. If the engine stops, the pump also stops. Petrol consumption is normal and everything else seems fine.

Can anyone advise please

 

[Malcolm Brown]

Fuel Pump

Paul

Are you sure it is the fuel pump? Can you narrow down exactly where the buzz is coming from? If so, I'll have a listen to see if mine is similar or not.

 

[Paul Woodman]

Fuel Pump

Malcolm,

Thanks for reply.

Yes, I'm pretty sure it's the fuel pump. If you look under the rear of the car, it's exposed. When you first turn the ignition on it runs for a couple of seconds to pressurise the fuel line then stops.

As soon as the engine is running the fuel pump runs continuously. This is probably because it's pumping fuel around a loop circuit and returning unused fuel to the tank to prevent vapour locks occuring in the fuel line.

It sounds normal in that that's how fuel pumps sound. It's just that it sounded louder than I'd expected.

Perhaps I'm just out of touch with how cars sounded in 1987, but as a new owner I want to make sure all is well, particularly because I have a long trip planned very soon.

 

[Andy]

Fuel Pump

Hi Paul,

My experience is that a little noisy fuel pump is ok. Its not even guranteed if you put a new one on. It will cure it. Long as it dosn't sound stained. Then dont worry.

Most of the cars do it with no adverse problems.

Regards

Andy @ www.mercedesserving.com

PS. You dont mention how many miles your vehicle has covered?

 

[Paul Woodman]

Fuel Pump

Andy

Thanks for advise, the pump does not sound strained, just a bit on the loud side. I'll let things carry on and see how irt goes.

In answer to your query, the car has done 71,000 mls.

 

[Malcolm Brown]

Fuel Pump

Paul

I said I'd have a listen to mine, so I did. Nothing noticeble with engine running. However, I'm certain you can rely on Andy's advice on this. And I'll save this thread for future ref!

 

[Andy]

Fuel Pump

Hi Paul

I wouldn't say that 71k is excessive. Just keep an eye on it (or ear) as the case may be.

Regards

Andy @ www.mercedesservicing.com

 

[JohnG]

Fuel Pump

The electric fuel pump on my started to emit a louder than usual buzzing noise and, for several months, this had no adverse effects on the running of the engine. But then the engine began to show intermittent losses in power and, sometimes, it was impossible to get the car up to 30 mph. I took it to a Mercedes dealer but, because the fault was intermittent, they couldn't find anything wrong. I also mentioned the buzzing fuel pump and was told that noisy poumps were not necessarily a problem and that it would be unwise to change it simply because of the noise. However, driving the car reached the point at which the sudden losses of power became dangerous. In desperation, I bought a new pump and fitted it. Since then, eveything has been fine.

(There are a few obvious risks in changing a fuel pump - especially the risk of fire)

John    

 

[csilk]

Fuel Pump

If you were preparing to spend any money on the car soon I would certainly say think about getting another fuel pump so you have one ready to fit.  There are 2 schools of through (within the MBOC anyway) 1. pumps often become noisy with age but this does not necessarily indicate immediate impending failure and  2. quiet pumps seldom fail- noisy ones do so it is likely to be on the way out at some stage.    The pumps from Eurocarspares are thought to be fairly reasonable, if not try Julian Larkin at should have some nice quiet second hand ones  e-mail julian@mercedesparts.plus.com