Fuel pump relay socket issue

[KarlHerman]

Hi.

New owner and new member. 1978 911sc
Already learnt a lot from this forum, and now this is my first post.

I was driving yesterday, everything worked fine as usual. Parked the car in parking garage for about 3 hours, started up (took maybe 1-2 seconds longer then usual to start) drove towards the exit and it started to sputter, like it was out of fuel (3/4 tank tho) and then just died. Managed to get it started a again a couple of times (had to give throttle for it to start) but only for a couple of seconds before it died again. Had to tow it home.

Was immediately thinking fuel pump, when I was hot wiring pin 30 to 87a nothing happened and felt bummed to have to get a new pump but then just to be sure I checked with a voltmeter to see if there was any power in pin 30 and nothing, 0 volts. The fuel pump fuse is good and I checked the next relay over and that one has good voltage in it’s pin 30.

Before I tear out the relay socket, am I missing something else? Is there another hidden fuse or somewhere where it might have come lose?

Also is it safe to run a lead from the neighboring relays power pin to the fuel pump relay just to get it working?

Thanks, appreciate all the help I can get.

[Flat6pac]

You need the key on for 30 to be hot. The relay feeds the fuse power to the fuel pump
Bruce

[pete3799]

Just to make sure.......you tested with the key switch in the on position correct?

edit: What Bruce said

[KarlHerman]

Thanks.
No I didn’t , now with the key on I have power on pin 86 and 87a.

[KarlHerman]

And swapping the relay now gets the car to start, runs super nice for a minute and then just dies again.

[boyt911sc]

Originally Posted by KarlHerman

Thanks.
No I didn’t , now with the key on I have power on pin 86 and 87a.

Karl,

This is normal. To understand how the FP relay and FP relay socket work better, read DKLever48’s thread about this subject. Everything you need to know is well discussed in this thread. Ask questions after you read it. Right now, you are doing a lot of quess work. Keep us posted.

Tony

[KarlHerman]

Originally Posted by boyt911sc

Karl,

This is normal. To understand how the FP relay and FP relay socket work better, read DKLever48’s thread about this subject. Everything you need to know is well discussed in this thread. Ask questions after you read it. Right now, you are doing a lot of quess work. Keep us posted.

Tony

Yeah I kinda wished I just found the problem and that it was a “simple” electric issue but now it seems more like a fuel supply problem...
back to the investigations

Thanks

[KarlHerman]

Problem(s) solved, it was the fuel pump and the fuel pump relay.
Now runs like a champ again, thanks for your help.

[Ian Comerford]

Strange for it to be both parts faulty?

[KarlHerman]

Originally Posted by Ian Comerford

Strange for it to be both parts faulty?

+1 on that.
Could the broken fuel pump have made the relay to brake maybe?

[boyt911sc]

Originally Posted by KarlHerman

Problem(s) solved, it was the fuel pump and the fuel pump relay.
Now runs like a champ again, thanks for your help.

Karl,

If the culprits were the FP and FP relay, it would take a couple of minutes to diagnose them if you read and understood DKLever48’s thread. Glad you have the car running again.

Tony

[pmax]

Well done.

Which relay did you buy ?

[KarlHerman]

Originally Posted by pmax

Well done.

Which relay did you buy ?

Thanks!
The new "Made in china" one. So far it does the job.

I'm quite new to Porsches but looking forward to learn more and do more. Just ordered the "101 projects for your Porsche". Next on the todo list is a new clutch cable and new brake lines.