Fuel pump not getting power

[shbop]

Having power problems to the fuel pump circuit, on my 81sc. The fuel pump relay is getting power through both 86 & 87a., but not out at 30. When I reach in to see if I can feel the rpm relay energize, it's too hard to tell with the buzzer going. I pulled the buzzer but can't feel the rpm relay energize. Should it energize with the buzzer removed? With the rpm relay removed, should the pump relay be able to work? Can someone tell me which two, of the four terminals, on the rpm relay to hook-up for a test?Or is it easier to jump the rpm relay socket? Thanks for any help. I won't have a wiring diagram until Wed.

[scarceller]

If you have power at 86 and 87a and the car is not running you should not see power at 30 till you start to crank.

So if you are looking for power on pin 30 with the key in 'RUN' position but the motor not running you won't have any power. Another thing to try is to locate the Air Flow Sensor and disconnect it this will trick the relay into thinking you have air flow in the intake and you should get 12v at pin 30 and the pump should run. The Fuel Pump relay circuit is not that simple. see this post as well: http://forums.pelicanparts.com/porsche-911-technical-forum/301127-fuel-pump-runs-constantly-post3033344.html#post3033344
As Doug, did a great job at explaining this relay circuit.

If you suspect the relay, which should be RED relay you could try to put a black relay in just for testing. The RED and BLACK ones are the same except the red one has a diode across the coil internally.

[shbop]

Thank you Sal. I was way off the beaten path. Excellent write-up. I had tried changing the pump-relay without success. I'll look at the Air Flow Sensor.