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AGD931 · Joined: 17 Mar 2003 Posts: 289 Location: Athens, Greece

I was out today with six other Porsches, generally enjoying ourselves on some winding roads, they drove home, I was "carried" by the tow truck....

Diagnosed as the fuel pump. Question is, I know that the smaller pump on the side of the tank is Ok as it "zizees" happily, but where is the main pump? Looking through PET it appears that it is separate from the tank and part number 911.608.102.02

Arthur
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1981 931 S2
1990 E30 320i Cabrio
1979 Ford Capri Ghia

Smoothie · Posted: Mon Sep 27, 2004 5:03 am Post subject:

You should have 2 pumps - one is inside the tank and all that's visible is the outlet end of it where the fuel line is attached. There'll be an "S" shaped hose from it over to the right where the main pump is mounted inboard of the rear right fender at the bottom - can't miss it - in fact, it is apparently the pump you were looking at. Buzzing from it is a good sign, but doesn't necessarily tell the whole story. My last pump was still running and buzzing after it went bad, but another sign it gave was that the sound changed pitch up and down rather than running at a steady speed. You'd really need to test the system pressure as I did - I found sys press fluctuating as the sound of the pump changed.

The second-to-last pic in this post shows the main pump location -
http://www.924board.org/viewtopic.php?t=6123&start=16
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Gregarious · Joined: 13 Sep 2003 Posts: 86 Location: Los Angeles

Did you ever ask, why two? Well, originally, the main pump was ok, until you angled up, or down, and the gas was lower. So, it quit pumping. So they added the second to get the gas at bad angles. You can run on just the one, but stay level, and accelerate 'normally'. I did, for awhile. Now, both are new. ;D
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Joes924Racer · Posted: Sat Dec 18, 2004 5:52 pm Post subject:

Will the car run with just the external pump not the intank pump
woeking.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Smoothie · Posted: Sun Dec 19, 2004 12:44 am Post subject:

Sure, it should run - the earliest 924s built came with just an external pump, but if you have an internal pump and it's not working, you have to figure it's blocking the flow somewhat.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Joes924Racer · Posted: Sun Dec 19, 2004 4:27 am Post subject:

Really when I switch external pumps I dont kink the s hose and the fuel flows pretty freely. I read about a post where a guy gutted his internal pump...Mine doesnt seem to be working and I have a full tank of gas too.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

924martinirossi · Posted: Sun Jan 30, 2005 2:23 pm Post subject:

That was probally me as I removed the internal fuel pump and just left the fitting. I removed it from an 80 931 and had no problems.

Michael

goturbo · Joined: 15 Jun 2004 Posts: 88 Location: Massillon Ohio, USA

Since I an in the middle of a restoration, should I loose the internal pump and replace the external one?

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

I'd replace, or make sure that both are functional. While the car is capable of running using just the external pump, the one inside the tank helps provide "pre-pressure" to the external one. Remember, the pressures in the fuel system are pretty high, and the external pump is the one that supplies the operational pressure. Without some help from the internal pump, you may be condemning the external pump to a shorter life. ...and we all know that these things are not cheap.
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'79 Eurospec 931

goturbo · Joined: 15 Jun 2004 Posts: 88 Location: Massillon Ohio, USA

Good piont. I was planning on repalcing them both so I will. Thanks.