fuel pump working, but not

qawse · 05-06-2005, 06:06 PM

My late '85 944 has bine sitting for quite awhile. When I decided to start it, the fuel pump was unresponsive. I checked everything, fuses, wires, etc. Anything I thought could be the problem I checked. I got the pump checked and it seemed to work, it buzzed like hell. So, I want to see if anyone could help me solve this problem. Also, when I turn the key, not to the point where the engine turns-over, there is a buzzing sound come from inside the car, not the fuel pump. This sound comes from the fuzz computer area, and is quite loud. Thanks for any help.

SoCal Driver · SoCal Driver's Garage

Fuzz computer?

Fuel pump only runs when the engine is being cranked and after it starts. Did you expect to hear the fuel pump with just the key turned on?

You can jump it to test with a jumper between the #2 and #3 fuse on the 8 fuse panel. Count from the drivers door.

With the key on:

Do you have power at the coil?

Power at the injectors?

If power at the coil AND at the injectors pull a plug wire, stick a spare plug into the end and lay it on the intake where you can see it from the drivers seat. See if you have spark when you crank the car.

If no power to the coil it's the ignition switch. If no power to the injectors but to the coil it's most likely the DME/fuel pump relay.

qawse · 07:21 PM

There is a buzz sound from inside the car, I dont know if it is related to the pump problem. The fuel pump is not pumping any fuel, but I got it tested and it seems to work.

bryanthompson · bryanthompson's Garage

I ran into something like this when I had to replace my battery yesterday. On my positive battery post, I have a bunch of 'extra' connections to things like alarm and radar detector (old school one) and whatever else the PO hotwired in there. Well, the connections were dirty, and the alarm wasn't getting power. I didn't know it, but the car would just crank and crank, but not fire. I have an extra DME relay, so I popped that in, but it didn't do the trick. Eventually, I just cleaned my battery connectors and tightened everything down. After I had good contact to the alarm, it started right up.

Sooo... does your car have an alarm? Does it whistle at you if you disconnect/reconnect the battery cable?

tuned944 · 05-08-2005, 08:38 AM

If your car is equipped with a factory installed alarm system, it could be the source of your problem. The alarm is tied directly into your DME. The fuel pump will generally operate when jumpered but will not through the normal relay. You can find detailed instuctions for bypassing the alarm at www.clarks-garage.com. I hope this helps!

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by qawse
There is a buzz sound from inside the car, I dont know if it is related to the pump problem. The fuel pump is not pumping any fuel, but I got it tested and it seems to work.

You have to answer my questions. There is a reason for asking these. It's called Factory DME Testing Plan.

Otherwise there is no common ground for a techincal disscussion.

qawse · 05-08-2005, 03:36 PM

Did you expect to hear the fuel pump with just the key turned on?
Yes, it says so in the Haynes manual.
Do you have power at the coil? I believe so

Power at the injectors? I believe so
I have not had a chance to conduct these tests yet, sorry
The fuel pump seemed to work the first time I turn the car over, but for different reasons it did not start. Namely, I was having starter issues, which have been resolved.
But, I did open up the fuel rall and then turned the car over, no fuel came out.

qawse · 05-08-2005, 03:47 PM

Concerning the alarm, I believe it was removed. Anyway, if it was not it ran for years without its use. So, do think that after sitting for a few years it could be the source of the problem?

SoCal Driver · SoCal Driver's Garage

What page of the Haynes manual says that the fuel pump will run with just the key on. We would like to check ours.

Come back when you run the tests. Until then you are just guessing.

qawse · 05-08-2005, 06:59 PM

wow calm down socal. I didn't mean to offend you. It does say turning the key on, after removing the fuel rail cap, and measure how much fuel comes out for 30 seconds (page 111, #6). When I did that nothing happen. Also, as I have already commented on, the fuel pump seemed to work, briefly, and then not again.

AFJuvat · 05-08-2005, 07:07 PM

Check to see if you have injector pulse and spark

test injector pulse with a noid light ($3.99 at any auto parts store - get the one for Bosch systems)

If you have no spark or no flash on the noid light when cranking, you either have a bad DME relay or a bad DME.

If you have spark and flash, you have a problem somewhere in the fuel delivery system - perhaps your pump or your tank outlet is gummed up from sitting.

AFJuvat

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by qawse
wow calm down socal. I didn't mean to offend you. It does say turning the key on, after removing the fuel rail cap, and measure how much fuel comes out for 30 seconds (page 111, #6). When I did that nothing happen. Also, as I have already commented on, the fuel pump seemed to work, briefly, and then not again.

That's instruction #6. Instruction #5 tells you to put a jumper between pins #30 and #87b on the fuse/relay board where the fuel pump/DME relay is. #30 is the switched power from the key. #87b is the circuit to the fuel pump.

The same thing can be done with a remote starter push button from fuse #2 to fuse #3 as mentioned in a prior post.

As was said before and for the last time the fuel pump does not run with just the key. The engine has to be cranking or running.

PLONK!

Baza · Baza's Garage

Tip just because it make a sound and seems to be pumping. Does not mean it is.
Past experience post search No Fuel Supply