911 sc fuel supply problem

[Guest]

Hi, my first post here..

I have a fuel supply problem with my SC.

To cut it short the engine will start but as soon as the ingnition key is released to normal running position (starter motor cuts) then the engine dies. I've established that the fuel pump is being turned off as well.

If I jumper the fuel pump relay the car runs fine.

I have a new fuel pump and fuel pump relay (the red one)

There is an immobilizer fitted but that seems to be working correctly.
Car is in for paint and some systems are disconnected like, horns, lights, etc.

I was wondering if I had one of the wires at the starter motor connected wrong?
Any ideas?

Thanks
Mart

 

[Guest]

Mart,
I have read this a couple of times and have a question for you.
I assume when you say jumper the relay you have in effect hard wired the relay out so that the fuel pump runs continuously. Also when you have done this did you start the car on the starter in the normal way and when you released the key the car continued to run.
Cheers
John

 

[Guest]

Hi John,
Yes I hard wired the terminals ( and removed the relay) and then started the car in the normal way. When this is done the car runs when the key is turned and it continues to run when the starter is stopped.

Any ideas?

Thanks
Martin

 

[Guest]

Martin,
From the outside looking in I would suspect the fuel pump relay and contacts.
So are you confident that the fuel pump runs when you turn on the the ignition with the fuel pump relay fitted? check that the fuel pump is drawing a current with a digital volt metre.
Just a thought, it might be that the fuel pump relay does not switch on the fuel pump and because the fuel system is pressurised via the accumulator to aid starting the engine will start momentarily and when the pressure decays the engine will shut down.
John

 

[Guest]

I suspected the fuel pump relay...

But the relay and the fuel pump are new. The car has been off the road for 9 years....

The pump definately runs when the ignition switch is turned all the way round to energize the starter motor. Its when the starter motor it turned off that the fuel pump stops running..

I have to say that the when the iginition is turned to the 'on position' (with the control lights for oil and alternater illuminated) that the pump dosen't pressurize the system. the pump only runs in the above scenario.

I have checked the fuel pump relay socket and cleaned the contacts.
Maybe the ignition switch is a fault?

Regards
Mart

 

[Guest]

Mart,
This is certainly on odd one?
As you stated before when you hard wire the relay out everything is ok, so the contacts in the relay area would be the first place to look and the ignition switch contacts next. Check the wiring with a continuity metre.
Also a long shot try another relay, borrow one from a friend.
Good luck
John

 

[Guest]

Hi,
Thanks for the thoughs.

I have one new red relay, one old red relay and a black relay.

Is it common for the iginition switch to fail?

Do you think it could it be related to the immobilizer? I've replaced the backup battery in that to no avail...

Regards
Martin

 

[Guest]

Martin,
If you could bypass the immobilizer for a test then I would, that would give you more information. Also as a test have you tried the other relays you have?
With regard to the ignition switch failing I don't know but I would at least check the contacts and from a wiring diagram check the continuity of the wire runs to the fuel pump relay.
John