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earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

My 931 won't run unless I put a hot wire directly to the fuel pump terminal. I did some preliminary checking, the multi meter says that the hot circuit has continuity when everything is off. In other words, sounds like its grounding out somewhere. Does this sound familiar to anybody? Jumpering the pump relay terminals does nothing. Also the pump won't run when I use the electric mirrors (this is a freaky 931 phenomenon--try it sometime. Engine off, key on, adjust your mirror and listen to the pump run; I remember a thread way back talking about this and I remembered it happening in mine, too)

Not real great with wiring--I guess I need to start with the 15 terminal on the relay and work backwards?
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1980 931 w/88K, decorating a field for 3 yrs.

earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

what I meant by continuity is that if I put the meter leads between the hot terminal of the fuel pump and ground, there's continuity ... which ain't right, is it? means it's grounded
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1980 931 w/88K, decorating a field for 3 yrs.

earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

so I have the problem traced to a fat green and black wire that sends 12V to the fuel pump. There's a connector inside the mass of wires behind the fuse block--past the connector the wire goes out through the firewall into the engine compartment (multi meter says it's grounded... shouldn't be, I don't think, since it's a 12V+ supply). Then it disappears. I have followed it, I think, into a fat bunch of wires that are kind of pinched between the side of the power steering booster and the firewall. Does anybody have the slightest idea where this wire eventually leads? I've looked at the current flow diagram in the manual, which isn't telling me much. It doesn't even give the colors of the wires.

Seems like that wire ought to make at least some passing reference to the fuel pump relay, but it just cruises right on past out into the engine bay...
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1980 931 w/88K, decorating a field for 3 yrs.

Smoothie · Posted: Mon May 04, 2009 2:48 am Post subject:

What diagram are you looking at? The one on Haynes pg.258 shows the black-green wire (labelled "2.5 bk/gn") at current track 18.
From that you can also see it links to a re/wt wire just after the fuse panel leading to the wur and aav. -Both of those, due to their built-in heating coils and probably the fuel pump motors themselves, would account for multimeter reading suggesting that the bk/gn wire is grounded. Actually, if set at a correct range the meter should show some resistance and not 0 ohms.
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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

earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

yup, smoothie--
the "grounded" black/green wire was my own little red herring. It's always the simplest, stupidest stuff--I finally got smart and put 12V to the #30 terminal at the relay and it fired right up. The fat red w/thin blue line wire leading off #30 terminal read 2V so I realized that was the problem. Turns out it was a broken ring terminal that I had replaced the old crappy one with at the battery. NAPA garbage. Broken underneath the heat shrink insulator.

Thanks for the help.

Onwards to the passenger window that won't go up or down ...
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1980 931 w/88K, decorating a field for 3 yrs.

earling · Joined: 24 Oct 2007 Posts: 105 Location: Lenox, MA

I have an '81 so I was looking at pg. 13 in the Supplement. The print is lousy so you can't see the "bk/gn" on the page
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1980 931 w/88K, decorating a field for 3 yrs.