fuel pump relay

[nuts4porsche]

my fuel pump relay is rusty and shot,can i jumper the relay to see if it starts? does anyone have a pic of it also? 80 US auto-thanks all!

[nuts4porsche]

i remember a thread on here about it,dont know to much about relays so if someone can guide me through it that would be great. i have a jumper made just dont know which terms. to connect to.

[MPDano]

If you look on the relay, it should have a diagram. I believe it's 30 and 87, but make sure someone chimes in to verify this.

[MPDano]

I found this pic. It is indeed the 30 and 87

[nuts4porsche]

thanks so much,i didnt want to be wrong and have to put a fire out! i made the same jumper but in white so i could see it browning if it was wrong.thanks again i dont get to mess with her but here and there so its nice you guys are on it! i will be replacing the relay,just want to see where im at. bad wiring/relays in panel.

[nuts4porsche]

hers a pic of my FP relay,just to make sure 30-87 same numbers

[stepson]

Yes. Terminal 30 has 12 volts. When bridged to terminal 87, it completes the circuit of the relay and allows the power to go to the fuel pump. On the spade end of the relay, the teminal numbers are stamped next to the male ends to help you know which is which. IIRC, terminal 30 is the male spade turned perpendicular to all the others and terminal 87 is the male spade directly opposite it.

[MPDano]

Also, pretty sure each spade is marked with the corresponding number next to it's spade.

[DPW928]

If you look at the bottom of the relay you'll see the spades are labeled. If you jumper the 30 and 87 connections, the pump will run continuously. If you jumper the 15 and 87 connections, the pump will only run when the ignition switch is in the on position. Jumping either bypasses the safety feature in the relay that shuts the pump off if the engine stops running during an accident, etc.

[nuts4porsche]

sweet, thanks guys! the more info the better

[Danglerb]

You might also consider replacing the relay, less chance of releasing the magic smoke.

[drwdds]

DPW928.....what is the mechanism that causes the fuel pump relay to shut off if the motor stops running? Am having trouble with a hot-start issue that gets resolved by switching out one fuel pump relay for another one that is "cool" after sitting in the glove box....wonder if it is temperature related.

[DPW928]

Originally Posted by drwdds

DPW928.....what is the mechanism that causes the fuel pump relay to shut off if the motor stops running? Am having trouble with a hot-start issue that gets resolved by switching out one fuel pump relay for another one that is "cool" after sitting in the glove box....wonder if it is temperature related.

The relay has to get a signal from the ignition module (circuit 31b IIRC) to power the fuel pump. It sounds like the relay has corroded connections or the wiring behind the relay panel is corrided. Any corrosion will increase resistance as the wiring heats up which could cause the relay to loose it's signal. If the external connections look OK, you might try pulling the cover off the relay and cleaning the contact. One other area to check is the ground that comes off the fuel pump and connects to the body. If that is loose or corroded it would affect the whole circuit. WYAIT I would check the battery ground also.

[drwdds]

Thanks, Dennis. That confirms my thinking that I'm going to have to do the long-put-off circuit board rehab I've been dreading...guess that is a right of passage all of us 928 owners have to do at some point!

[nuts4porsche]

im in the middle of doing it now,the back wires are done and im on the fuse spots on front now-not fun!