Fuelling problems with 911 SC.

Rhyd911 · 02-18-2002, 01:46 PM

Hi,
Sorry this post is a bit long, but this fault is really getting on my nerves now with regards to solving it. Car is a '78 SC with K-Jet fuel injection.

The problem started recently when I tried to start my car.

It fired up pretty much as usual, but I noticed that it was barely ticking over. I left it running for a couple of minutes and the revs started to pick up.
However as they did, the fuel pump started making a buzzing noise which increased in intensity as the revs built up. All of a sudden the pump would go quiet and the engine would then cut out. Restarting the engine produced exactly the same results. When I put my foot on the throttle, sometimes the engine will rev and sometimes it will just cough and splutter. When it does rev up there is always the buzzing noise again, getting more noisy with engine speed. It then goes quiet and the engine cuts out.

I immediately thought of the fuel pump, which is quite old, so I have replaced that with a new Bosch item. Unfortunately this did nothing to solve the problem.

I have now cleaned out the fuel tank screen, and replaced the fuel-in hose into the fuel pump but the problem was still there.

After I did that, the car behaved the same with the same buzzing from the fuel pump, noise stopped,revs increased and then the engine died.

Now the car will not start it at all (as in starter motor turns engine over but it will not fire).
Have cleaned up the terminals on the fuel pump relay, tried a black relay that I know works, and cleaned the fuse.

Also when I manually lift the sensor plate in the fuel distributor I no longer get the change in noise on the CIS box or any resistance suggesting the fuel pump isn't activating at all now.

Has anyone had any experience of this? This is driving me mad?

TIA
Rhydian

wckrause · wckrause's Garage

Here's the schematic for the circuitry around the fuel pump relay.

schematic

Does your car fire up at all? You could try jumpering the fuel pump relay just to see if the pump runs. Maybe it's the ignition switch.

Rhyd911 · 02-18-2002, 02:15 PM

Hi,
Thanks for the reply. No the car will not fire at all any more.

Will try the jumper, but maybe tomorrow!

R.

Otto · 02-18-2002, 04:37 PM

If the jumper doesn't work and you are still having running problems, call Francis @ Tuthills workshop in oxfordshire on your island. His number is 44 (0) 1295 750 514. OTTO

stormcrow · stormcrow's Garage

What you need to do is check to see if the relay for the fuel pump is the culprit. Sometimes when the relay goes, it will buzz awhile before it quits. Turn the ignition key to the start position with radio off and listen for the relay to click. If it does then the fuel pump is your problem and that needs to be checked next.

You can jumper across 87a and 30. If that starts the fuel pump then the relay is the probelm.

To check the fuel pump apply 12v (+) to the black terminal on the fuel pump. That should tell the story.

Steve

Rhyd911 · 02-19-2002, 07:15 AM

At the moment, when I turn the ignition to point 2, I can hear the fuel pump relay click. There is then a dull thud from somewhere (cannot trace this at the moment).

When I then further turn the ignition so that the starter engages, I can hear the relay ticking from the front of the car.

To my mind the relay should be constantly on at this position and not switching as it seems to be. Sounds like it is the relay, so I will get another one. Will try the jumpering techniques aswell just to check.

Thanks guys!