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Audi 4000, Coupe/GT: 1980-1987 (B2) fuel supply?


Permlink Replies: 6 - Pages: 1
Last Post: Mar 11, 2008 6:26 AM Last Post By: cowinthefog
cowinthefog

Posts: 36
Registered: 06/23/07
fuel supply?
Posted: Feb 18, 2008 5:44 PM
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I have a 1984 Coupe GT, 2.2 liter engine. Does anyone have any idea why when I turn the key to start it, the fuel pump only runs for about a second and a half? I thought it was a bad connection, but checked and it seems to be good. I have power at the battery feed terminal and and the switched terminal. I am not ruling out a bad connection, just that I didn't find one initially. What could cause the fuel pump to come on for that short period of time, no matter what I did, whether turning the ignition on and off, or wiggling the wires, the time the pump ran for was always the same. Is my relay shot and just can't hold the connection? Thanks, Josh
FKH161

Posts: 7,661
Registered: 12/29/05
Re: fuel supply?
Posted: Feb 18, 2008 7:11 PM   in response to: cowinthefog in response to: cowinthefog
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That's the priming circuit, which is normal.

Once the engine is cranking or running, the relay receives
an ignition signal which keeps the relay/pump energized.

No crank/ignition signal = relay/pump shut off (safety
feature in case of fire in an accident).
cowinthefog

Posts: 36
Registered: 06/23/07
Re: fuel supply?
Posted: Feb 19, 2008 4:21 AM   in response to: FKH161 in response to: FKH161
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That sounds good. I am trying to flush the fuel tank. How can I safely get a constant signal to the fuel pump to pump out the cleaners I put in the tank? hot wire it for a couple minutes? I am relieved to know the system is functioning properly so far. Thanks, Josh
FKH161

Posts: 7,661
Registered: 12/29/05
Re: fuel supply?
Posted: Feb 21, 2008 10:24 AM   in response to: cowinthefog in response to: cowinthefog
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Sorry about the late reply.... find & remove the fuel pump
relay. On the side of the relay should be a circuit diagram
with numbers for each pin. Bridge #30 & #87 with a fused
jumper wire... this will provide power to the pump as long
as the jumper wire is in place.

Find a good place (easy to get at) to disconnect a fuel line
where you can allow the fuel to escape into a bucket... you
could also disconnect the return line going back into the
tank... that way, the fuel leaving the pump runs through the
whole system (with the cleaner) before being drained/dumped
into a bucket.
cowinthefog

Posts: 36
Registered: 06/23/07
Re: fuel supply?
Posted: Mar 9, 2008 12:50 AM   in response to: FKH161 in response to: FKH161
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Thanks for the tips, I have got the car running now and it seems pretty good when warmed up, but runs a bit erratically when cold, though it doesn't stall. It will stall, when cold, if I hit the gas and let off. Any clue on that one? Thanks, Josh
FKH161

Posts: 7,661
Registered: 12/29/05
Re: fuel supply?
Posted: Mar 9, 2008 1:48 AM   in response to: cowinthefog in response to: cowinthefog
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Check the coolant temperature sensor (for the ECU) and the
differential pressure regulator (at the side of the fuel
distributor) miliamps while the engine is running.

The ECU varies the miliamps going to the regulator, thus
changing fuel mixture. If you are not getting any current
to the regulator, it could be that your ECU is not powered-up
and the system is running on pure mechanical fuel metering.
cowinthefog

Posts: 36
Registered: 06/23/07
Re: fuel supply?
Posted: Mar 11, 2008 6:26 AM   in response to: FKH161 in response to: FKH161
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I haven't had a chance to check anything yet, but I did go and get the emissions test done today. It passed fine, but on the way home, it started running rough, as though it were missing on several cylinders. It seems to be fine at idle, but little beyond that, and it sputters and misses. It never stalled on me, but ran rough. I checked a couple plugs when I got home, and they looked alright, albeit a bit too white(leaning out?). I know I have a small leak in the line from the EVAP canister up near the fuel line connections just forward of the shock tower. Is my ECU temp sensor the big round thingey with two screw on wires below the warm up regulator? I will start testing tomorrow. Thanks, Josh

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