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That could be a problem... (archive)
[ Follow Ups ] [ 7-series (E32) Message Board ] [ Msg. Board FAQ ]
Posted by R.Mui on December 06, 2000 at 21:30:24:

In Reply to: Re: Crazy, isn't it! posted by Max Fretter (NZ) on December 06, 2000 at 04:02:41:

As I have a bad habit of filling the gas tank only half way to save weight. Guess it does allow water to condense within the gas tank and could be the cause of my problems. =(

Anyhow, it's strange as it hasn't happened these 2 days straight. The only difference being that these couple of days I have a half tank of gas in there and the noise occured most when I had oly about 10% of the gas tank filled. So the reduced pressure could be making the pums work harder, causing the noise?

The reason I fill the car only half way is because here in Hong Kong most traffic I get is stop-n-go and the mileage decreases by quite a bit if I have a full tank of gas in the car. Guess I didn't think about the problems this could lead to would be more expensive than the money saved with the lower gas consumption. =(

Richard


Just had the pump etc out (of the tank, I've got a 735) and the output of the pump has a fuel pressure regulator (looks like a mini gas regulator like you'd get on a barbque gas tank) before it goes to the hose - if the diaphragm has
relaxed, maybe you're getting an oscillation in there. Try finding the pump and listening to it while someone races the engine for you - the extra petrol demand might kill the oscillation, and if it does you know it's the regulator.

Also must remember that
1) roller pumps are prone to wear and noise - the rollers can get looser with age
2) the rollers should be lubricated by the petrol going thru the pump (the whole motor is immersed in petrol - no oxygen so no explosion. NEVER run a pump without petrol going thru it - can cause a residue vapor explosion)
3) they can get rust if there is water in the petrol
4) they can theoretically suffer from bubbles (in the body) if the body is mounted horizontally
5) they MUST have the inlet filter gauze in place to stop clogging and/or wear - if you have an externally mounted pump, have you checked the inlet filter in the tank?

I must admit, both my BMW EFI motorbikes have the original pumps after 18 years...

Max Fretter


>>I mean, with the pump that came with the car and the one that I replaced about 4 years ago, this next one would be the third.

Anyhow, just called BMW service here and the "service advisor" mentioned that the "regulator", instead of the pump itself, could also lead to the buzzing noise...any idea about that one?

I think it probably isn't something as simple as a clogged fuel filter, no? I don't think I'd be that lucky...

Richard




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