cc1979

Does anyone have a link on how to jump the fuel pump relay to run it without starting the vehicle? That or a quick explanation? I have searched and searched and find a lot of references to people doing it. I'm guessing it is pretty easy to figure out because a lot of people are doing it but I'm not sure myself. Thank you,

Shark2626

Pull the relay out of the car, on the back of the relay it has numbers, you want to bridge 30 and 87. Take your relay to an auto parts store or a hardware store and buy a small pack of spades that are the same approximate size as the spades on the back of your relay, and a length of wire that will fit in the spades you buy. Make your wire out of 4' or so of the wire with a spade crimped to either end. Then insert the wire between 30 and 87, you should hear your fuel pump working from the rear of the car. It will keep on running as long as that wire is in place, so remove it when you are done. If you want to be fancy, add a switch in the middle of the wire to turn it on and off without removing the wire.

jpitman2

I use 6ft or more of 2 core flex. 1/4" Spades on both wires at one end, and a switch at the other end - momentary are safest - only closes when held down, so if you drop it the circuit opens. With this length of wire you can make it work from anywhere around the car - up in the engine bay, or at the rear checking the pump.
jp 83 Euro S AT 57k

cc1979

Thanks guys. That worked. The fuel pump wouldn't pump anything but it was getting hot so I know the power was going to it. I'll have to keep troubleshooting.

ALKada

Clogged ?

dzaprev

Why do you have to keep trouble shooting? Your pump is locked up sounds like.

jpitman2

Reverse the polarity to the pump briefly, it may spit out the obstruction - worked for me!
jp 83 Euro S AT 57k

Mrmerlin

take the pump out of the car and then test it .

NOTE since you figured its already not pumping reversing polarity while its still in place will put the dirt into the tank.
Also include the year car your working on as different years have different fuel pump relays

Petza914

My switched jumper

cc1979

Thanks for the heads up on the lack of details. I thought I had put in my signature somewhere the car I had. It's a 79 and has an internal fuel pump and an external behind the tank fuel pump. They are both out of the car now. I'll try to reverse the polarity on the external and see if anything happens. Is there an easy way to test these on a bench? Also, If one is acting up will it still run as long as one of them is still functioning? The car has had some troubles where it would randomly leave the prior owner stranded and then just start up like nothing was wrong.

Petza914

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I don't believe the car will run if either pump isn't working, as it not spinning blocks the flow.

928s randomly stranding people is often a faulty fuel pump. My 79 has stopped running or wouldn't restart (would crank) twice during my ownership. Both times it was the fuel pump relay. I carry 2 spares in my toolbox in the car, along with the jumper.

jpitman2

IMHO toss the internal pump, tie back the wiring for it, replace with a screw in strainer. One external pump works for me on CIS, as long as you are not hot and high altitude.
jp 83 Euro S AT 57k

Petza914

Good advice from jpitman, but with the caveats. I live in SC where summer days can be 95 degrees with high humidity so I've kept the dual pumps - but also because of my supercharger setup and it's requirements for more fuel and in a shorter delivery window. I also have a wideband O2 guage to track AFRs.

hacker-pschorr

My 79 ran fine with the internal pump locked up. Problems started when the fuel pump relay burnt out and I started to investigate.

Sounds like he's having a similar issue.

I scrapped the internal pump in favor if a new external pump and tank screen.

jpitman2

Well, my car did ~10 years in Riyadh, at 3000 ft ASL, and summers temps of 120F, with just the external pump, so one is enough most of the time. With a supercharger I agree 2 is better/necessary. Read the threads about issues caused by the internal pump and its inadequate plumbing.
jp 83 Euro S AT 57k