930 no fuel pressure

cgebh · 12-21-2006, 03:26 PM

New to the forum, but have a question. I have read many threads on this, but still not sure. I have a 77 930 and do not have any fuel pressure. The car runs fine when I bridge pin #87 and #30 in at the forward fuse box (both pumps operate). I have seen treads stating that the overboost switch relay is bad. According to the parts manual, this car does not have a overboost switch relay (if it does, where is the location). What am I missing?

h20cooled7 · 12-21-2006, 03:49 PM

87 and 30 is your load side of the relay, alls you are doing is jumping the relay. you have to check for power and ground on the other 2 pins thats what gives you the signal to close the load side. you should have constant ground on 1 leg and switched power on the other leg.thats how a standard 4 pin relay works if you get me a wire diagram i cna help you more

cgebh · 12-21-2006, 04:00 PM

I am using the standard red relay. I got this diagram from another thread today. Could the ignition key switch be bad?

h20cooled7 · 12-21-2006, 04:09 PM

ok ,make sure the fuse is good,cover your ass and pull the fuse and make sure its not blown.
if the fuse is good reinstall fuse.
to check your ignition switch you should have power at the fuse you just checked
try that and let me know
pete

cgebh · 12-21-2006, 04:15 PM

I forgot to say that all fuses are new and have been double checked

h20cooled7 · 12-21-2006, 04:21 PM

you can bypass the ignition switch by putting 12 volts to the feed side of the fuse(the side that feeds the relay, i would put the same amperage fuse in line with your 12 volts ,just for insurance)if the car fires the relay and runs you have a bad ignition switch or faulty wiring to the relay
try that and let me know if that does it for you.
pete

A930Rocket · 12-21-2006, 04:22 PM

That diagram is for a 911SC, the 930 might be a little different.

Your fuel pump runs, but you need to check a few other things. Ground your overboost switch and see if it starts. Check the fuse as stated. Go to the engine compartment and check the yellow relay near the fuse box. Tap the relay and see if the car starts. Jump 30 and 87 there. pull the plug off the metering plate switch and try to start the car. Clean all your electrical connections.

cgebh · 12-21-2006, 04:23 PM

I will try that in the morning

A930Rocket · 12-21-2006, 04:25 PM

I bypassed all the rigamarole electrical by grounding the two fuel pump relays with an impact switch. Now when I start the carm, the fuel pump kick on, I start the car and it there is a shunt, the impact switch will kick off the pump.

I should have done it years ago....

h20cooled7 · 12-21-2006, 04:27 PM

the correct wiring diagram does help a lot
good luck bro

cgebh · 12-21-2006, 04:30 PM

A930 Rocket, I do not have a yellow anything around my fuses (engine area) I have a rea window defog relay only. Now I do have a plug that has been bridged (not sure what it is or was)

cgebh · 12-21-2006, 04:33 PM

I have all the service manuals and they explain how to check the pumps, but don't tell you what to check if the bridging trick works.

h20cooled7 · 12-21-2006, 04:38 PM

can you get a wiring diagram that has the wiring colors,fuse location #s and pin #S

h20cooled7 · 12-21-2006, 04:39 PM

im a vw tech and they are pretty damn good at that stuff ,I have to give volkswagen that much,but all german cars have a standard for the wiring on all german manufactures

cgebh · 12-22-2006, 11:09 AM

Thanks all, the problem was the TURBO PRESSURE SWITCH. Grounded connector (whire wire) to frame, fired right up.

h20cooled7 · 12-22-2006, 11:12 AM

NICCCEEEE!!!!!!

beepbeep · 12-22-2006, 11:32 AM

Quote:

Originally posted by cgebh
Thanks all, the problem was the TURBO PRESSURE SWITCH. Grounded connector (whire wire) to frame, fired right up.

The one that you tought doesn't exist?

It's function is to cut fuel in case your wastegate malfuctions. It's last resort that can save your engine and you should fit a new one.

A930Rocket · 12-22-2006, 12:09 PM

Glad you got it stated! Seems like it can be the simplest thing to keep it from starting sometimes.

BTW. That black round relay is where the yellow square relay is on mine.

Quote:

Originally posted by cgebh
A930 Rocket, I do not have a yellow anything around my fuses (engine area) I have a rear window defog relay only. Now I do have a plug that has been bridged (not sure what it is or was)