Fuel Pump stays on
Huw Powell
audi at humanspeakers.com
Thu May 7 10:49:25 PDT 2015
Hi David,
Do everyone a favor and reply to the list, keeping the conversation in
front of all eyes, ok?
Glad you got the FP sorted; good luck with the windows!
- Huw
On 5/7/2015 1:36 PM, David Vanden wrote:
> Got the fuel pump problem fixed. The fuel pump circuit had died on the
> car so the mechanic had jumped the fuel system from the rear window
> defroster in the fuse box. He did this a while ago and there were no
> problems. But then it committed to staying on When I changed the ECU I
> think I fixed the fuel pump circuit. I think the problem was that the
> mechanic still had it jumped from the rear window defroster so it might
> have been getting overload. Maybe that caused it to burn out. I don't
> know why it kept staying on however as this happened before I did
> anything. Anyway, removing the jumper and switching the ECU seems to
> have the fuel pump working correctly again.
>
> You are right there is no power window relay. The parts shop had told
> me there was a power window relay when I first told them what the
> windows weren't doing. I replaced it but it turned out to be the
> cooling fan or the horn relay or something. But I was still thinking I
> had replaced the relay for the windows.
>
> However, the windows are still doing the same thing. I don't know where
> the auxillary fuse relay panel is but I will sure look and try your advice.
>
> I may have more questions later. Thanks.
>
> On Thu, May 7, 2015 at 12:15 PM, Huw Powell <audi at humanspeakers.com
> <mailto:audi at humanspeakers.com>> wrote:
>
> OK, so it's 4kq week here on Audifans...
>
> There's a lot of ground to cover on this one, so bear with me.
>
> First, there is no "auxiliary" position for the ignition key. It is
> off, run, and start.
>
> So I'll have to assume you mean the "run" position, the first place
> the key turns to, and where it goes back to after releasing it from
> the "start" position.
>
> Now, in the run position, we want the fuel pump to run. Otherwise
> the engine won't. But there is a safety feature built into the fuel
> pump relay. It has a coil signal input, and if that stops, it turns
> off.
>
> So unless you habitually leave the key in the run position for long
> periods of time, your only "problem" is the loss of the safety feature.
>
> Now this issue would point to the fuel pump relay, or a short
> somewhere in the wiring that bypasses it somehow.
>
> The ECU only does a couple of things on this car - it manages the
> fuel mixture in response to the oxygen sensor output (and in
> response to the engine temperature), richens it at wide open
> throttle, and manages the idle via the ISV when the throttle is closed.
>
> Did you replace the FPR with an exact new replacement?
>
> Does the pump run with the relay removed?
>
> As far as the old pump dying, I suspect the problem occurred the
> other way around - the old pump might have been drawing too much
> current and melted some insulation, causing a short that allows this
> "pump always on when key is in run position" problem.
>
> Now to the windows.
>
> The ECU has nothing to do with them.
>
> There is no power window relay on this car.
>
> Power goes through the X relay (power on only when in run,
> accessories are not on in start position) to the switches, and then
> on to the rear switches and the window motors. There are a couple
> of circuit breakers, however (one for the windows, one for the roof,
> IIRC) They are little silver boxes about 1" x 3/4" x 1/2" in the
> auxiliary fuse/relay panel in front of the driver's knees. Try
> swapping them, or even briefly replacing the window one with a heavy
> wire and a 20A fuse.
>
> Also, one or more of your window motors may just be drawing too much
> current.
>
> You need to obtain the Bentley shop manual for the car, although it
> is possible a lot of the info in it is on the web by now.
>
> Fixing electrical gremlins properly on this car can be very
> expensive unless you can do it yourself, which requires schematics
> and a strong understanding of how everything works. However nice it
> may be in some ways, its value is not much higher than scrap (the
> demand for used parts has pretty much dried up).
>
> Disclaimer: It's been a long time since I even saw a 4kq in person,
> or at least a stock one. It's also been a long time since I
> memorized the electrical circuits in the car.
>
> I hope this helps a bit.
>
> - Huw
>
> On 5/6/2015 9:39 PM, dvanden46 at gmail.com
> <mailto:dvanden46 at gmail.com> wrote:
>
> I have a 1987 Audi 4000 Quattro. When I turn the key to the
> auxillary position the fuel pump stays on. It used to prime for
> a few seconds and then shut itself off. This is the second fuel
> pump that has done this and it is new so the problem does not
> rest with the pump. I replaced the filter. I also replaced
> the fuel pump relay and the x contact relay to be sure they were
> not the problem. I also switched out the ECU to make sure that
> was not it. I have done this and still the fuel pump stays on
> with the ignition key turned. I think this is what caused the
> old fuel pump to stop working.
>
>
> Also, the power windows will only work for the first few moments
> after I turn the ignition switch. After that typically they
> will not work. Again I changed the ECU and the power window
> relay and still the same problem. If anyone has any input I
> would be glad to hear it.
>
>
> David
>
>
>
>
>
>
> Sent from Windows Mail
>
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