Fuel Pump stays on

[Huw Powell]

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 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
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> http://www.avast.com
> _______________________________________________
> quattro mailing list
> http://www.audifans.com/mailman/listinfo/quattro
> http://www.audifans.com/kb/List_information
>