When removing the gas tank for a sway bar install I noticed that the fuel pump on my '75 had a different colored wire hooked up to it, and a stray wire not going to anything. It has always worked fine, so I ignored it.
Then I learned that the fuel pump is supposed to shut itself off after a few seconds with the key in the 'on' position.

Mine doesn't do that, it just runs continuously. While I do want undo whatever the PO did and wire it correctly, I don't have time to do anything now. My questions is will this hurt anything assuming I actually start the car and don't just leave the ignition in the position without it running?

Thanks-

Robert

Carb or FI?
If it's been switched to carbs the pump relay has been removed. If still FI then there's a hack somewhere.

I just went through this, maybe not the same situation as yours but same year.


I brought the car home and the PO had rewired the fuel pump to run contiuously while the ignition was on. He also installed nifty push button switch. The original wiring was left intact fortunately.

The BIG problem I saw was that the old lines could not handle the load , not sure if it was just the age of the lines or the pressure, but they were leaking pretty good.

Another problem that crossed my mind was the old wiring was left intact and could have possibly been live, not the best thing to have under a leaking tank.

It was fixed in a matter of an hour or two.

My vote is to fix it and forget it.

BTW
The reason the fuel pump wasn't working is because of a bad dual relay (1.8L L-jet)

The car still has it's original FI system in tact.




Yeah, I guess I need to figure it out and put it back to the way it should be. Maybe it was just a bad relay or something similarily simple that caused somebody to run another wire to it...

This was a Qwick fix on the 1.8 when the dual fuel pump relay failed. Not correct but will work.

Steve

you need to trace the current path through the relay board. the power to the FP is a wire that is connected to the relay board. verify the continuity to the FP but also verify the continuity to the ECU. the PO rewired it for some reason, maybe a broken wire in the sheathing. once connected to the ECU, it should work as designed.

So is there a relay that runs the pump for 2 seconds or so, or does the FI brain do this? Where is this fuel pump relay- on the engine compartment relay board I presume?

Maybe this will help.
1.7 and 2.0 D-jet
Click to view attachment

74 and 75 1.8 use a dual relay mounted by the battery stand.

Steve

That's a sweet diagram. Thanks!

There is a tech article that might help a bit:
Fuel Pump for Carbs

Actually it's kind of a convoluted circuit path.
If you look at the relay board photo, the fuel pump relay
drives +12v to the fuel pump when the coil is energized.
The +12v that gets switched to the fuel pump is live all the time and
comes from the red fuse in the photo; however,
the coil of the fuel pump relay gets +12v from the power supply relay
and the ground to the fuel pump coil comes from the FI brain/computer.

The Power supply relay coil gets its +12v from the ignition switch on the
same circuit as the coil.
The Power supply relay coil ground is always grounded.
The +12v that is switched by the power supply relay coil is live all the time
and is *not* fused.

So what that all means is that in order to activate the +12v to the fuel pump
you must:

- Have a fuse in the location where the red fuse is.
- Have the power supply relay plugged in
- Have the fuel pump relay plugged in
- Turn on the ignition switch.
- Ground pin 1 of connector T4b (normally done by FI brain)


--- bill

Hey guys,
could use some help, I have been working my way through fuel system problems on my 74 1.8L 914. I have been able to get the car running by jumping out pin 3 on T4b to ground, but it is the only way to keep the fuel pump running. I suspect it may be the dual relay but I don't see a connection on any of the prints that show a connection between the fuel pump relay coil, pin86 and any thing? my prints show that that connection only goes to t4b pin 3. the only connection that i have on T4b is a yellow wire that connects from T4b pin 2 to the dual relay board. How is the ground for the fuel pump relay supplied? I know that it has to come from the fuel injection controller somehow but I am missing somthing. I just got the car last week and it was not running so just getting it to run was quite a charge!!!! the motor sounds great only 21,000 original miles I did sneek in a short drive today just because I had to, this chain has been a great help in getting me this far so thanks for all who left coments!!!


Bob

[/quote]

74 and 75 1.8 use a dual relay mounted by the battery stand.

Steve
[/quote]

If you have Ljet it would be advised to not have a relay in the FP slot on relay board. On my 1.8 Ljet having a relay there caused a SUPER RICH running condition.

Good Luck
JKP

Strange you would mention not putting a relay in the FP socket???? When I started working on the car there was not one there. I just thought that it had been removed by the last owner when he was working on the fuel system. Will the pump work without the relay in that position if everything else is working correctly? Is the dual relay tied into the fuel pump circuit in some way and able to bypass the need for that relay? My electrical prints leave a lot to be desired when it comes to the interface between the controller and the fuel pump.

Thanks!!
Bob

I beleive having the fuel pump run continuously is dangerous in a crash situation. The way it was designed it should only run for a few seconds if the engine is not running. Wire it up correct to save burning to death.