Porsche Enthusiasts Club Forum

Hi Everybody.Wonder if you may shed some light on this?
My son has recently started a project to restore his newly purchased 924 Turbo. As a non-runner and having been off the road for 7 years the last owner claimed with fuel pump problems. So let me explain where we are so far=Fuel pump does work.Injectors all cleaned.Changed ignition control unit.Checked all wiring? All fuses checked/replaced.Fuel pump relay replaced.
Car starts but will not run for more than a few moments. Fuel pump does not seem to be ativated unless a wire to bridge the contacts.
When doing this it seems the petrol is flooding the cyclinders and getting into the oil(not supposed to)
So it comes back to the relay does not seem to kick in and out(or at all) keeping the fuel pressure correct at all times. We have tried both types of relay(6 connector with fuse on top)(5 conector with fuse in extra fuse box) The wiring diagram only shows the 5 connector version and we do seem to have only 5 wires!)

HELP!!!!

So can anyone shed some light?

We did have an autoelectrician for a day but although he found the coil was not giving enough spark he couldnt get it to run fully.

Thanks

Paul

Have you joined the PCGB forum and asked in the 924 section? There may be more 931 related experience there... (this isnt meant to ruffle anyones feathers. I remember when the 924&944 Enthusiasts Club started and I understand why, but on occasions each forum has its strengths).

Simon

I'm no expert but have you tried changing the petrol?
If it has been sat for seven years it may be useless now which was one problem I had. I drained down the tank and started with fresh petrol.

Does this use the K-Jetronic like the NA 924? If so I believe that the fuel pump only runs while the engine is running, this is a single from the distributor, there is a hall sensor setup inside.

I have had this fault on a number of Jetronic cars and have either changed or rebuilt the distributor.

Does is pressurise the fuel system when you put the iginition on and then fire and only run for a second which is all it takes to depressurise the fuel system?

To double check you can remove the distributor put the ignition on and turn the distributor as if the engine was running, you should hear the fuel pump buzzing, if not thats probably the problem.

Cheers

Neil

Agree with the previous poster.
Ensure the fuel pump is running - by bridging the relay with a jumper
As a series 1 turbo (I assume) - you have a fairly standard K jet set up with mechanical spark (as opposed to later digital spark set up).
Check you get fuel being delivered to the injectors - pull them (or in the turbo - unscrew them and check they activate when the pressure plate is depressed.
Check the cold start valve is not flooding the engine by staying on - you can simply disconnect it or pull the injector from the inlet manifold and watch it as you try to start the car.
Whereabouts are you?

I'm no expert on the 924 but I would not expect the fuel pump "to kick in and out" to control the pressure.

I would have thought it would run continuously and you will have a fuel pressure regulator somewhere.

Rich

That's right - the pressure regulator is on the mixture unit and is shimmed. But the pump should run continuously.

Hi there, to me it sounds like a duff fuel pump relay ( )and the mixture is way too rich when the jumper wire is in and the car running. As previously said, it could be the cold start valve sticking so may be worth checking (should spray for about 8 secs on n/a not sure if the same on turbo). It could also be that one or more of the injectors is leaking fuel after engine shutdown, so would be another avenue of investigation for you. To test for this just pull out the injectors one by one, connect to the fuel pipe and put into suitable glass jar or something similar, start and run the engine. You can check the fuel spray pattern at this point, it should be symmetrical and conical in shape. If this is ok, then turn off the engine and wait for 10 - 15 seconds, during which there shoud be no fuel coming from the nozzel of the injector.

If there is fuel coming from the injector after the engine has been switched off or if the spray pattern is not conical the injector concerned should be replaced.

Hope this helps you out.
Matt.