Fuel pump noises. Good/Bad?

[Adam]

I'm following up to Rufblackbird's post about fuel pump noises when the motor's off, but the ignition is on.

Before my 915 overhaul, the pump would make a "priming" noise and that was about it. A short 1-1.5 sec buzz and then silence.

Now, it buzzes constantly. It was the first thing I noticed when I got it back. I'm only slightly vexed as it seems harder to start (especially in colder weather) than it ever was before.

Perhaps my local P-car guy left a plug off somewhere or something. I only say before the 915 overhaul because I know that the motor & all was out. Perhaps during the refit, something was missed. Any ideas where I should be looking and what I should be looking for?

AC

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Adam Chaplin - 1976 911 Coupe
My Pelican Gallery Page
My Owners Gallery Page

[This message has been edited by Adam Chaplin (edited 07-02-2001).]

[This message has been edited by Adam Chaplin (edited 07-02-2001).]

[SeaDweller]

Mine was doing the same thing, and we troubleshot the heck out of it, only to find it was something as obvious as a bad fuel pump relay...........

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Michael
'78 911SC Euro

[sander]

My pump buzzes as long as the ignition is on, too. But I haven't experienced any difficulty with cold starts. Granted, I live in San Francisco, so my idea of a cold start is about 50 degrees.

Does the constant buzz mean there is definitely something amiss? I didn't even realize that that buzzing was supposed to go away after a couple seconds.

[wckrause]

If you have a schematic for your '76, look for something called an airflow sensor, or airflow switch. SC's have this, but I'm not sure if your '76 has one. If you have one, it will be located on the front of the airbox, between the throttle body and the fuel distributor. It's hard to find.

Some peole disconnect this to IMPROVE cold start, because it will ramp up your fuel pressure before you turn the key to START. It's function is as a SAFETY device to turn off the fuel pump if the engine quits running.

Here's a link to the SC schematic. The switch is called the air flow sensor contact and is at the bottom center of the picture.

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_Part1-2.jpg

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Bill Krause
'79 911SC Euro

[This message has been edited by wckrause (edited 07-02-2001).]

[This message has been edited by wckrause (edited 07-02-2001).]

[Adam]

Thanks for your input Bill!

I'll check it out sometime tonight when I get home. Also, I'm keen to inspect the fuel pump relay too. Thanks to Michael for his input.

I'll let you know how I do.

Thanks again

AC

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Adam Chaplin - 1976 911 Coupe
My Pelican Gallery Page
My Owners Gallery Page