Thread: Electric fuel pump won't shut off

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I recently brought my 23 T out of mothballs. After doing all the routine maintenance before taking it out, oil change/filter/fuel filter/brakes/ you know the drill, I cranked it up, and it ran great. A few short neighborhood runs to test for problems, and all was well. Yesterday, I took it for a little longer jaunt, and about ten miles out, it died. after 3 1/2 hours after starting, driving, and dying, I made it home. Seems as though the carb is pushing too much fuel into the engine, and flooding. But after checking a little further, I find that the electric fuel pump is cranking 15 to 20 pounds pressure nonstop, and the carb is not stopping it. I originally thought carb rebuild, Holley dbl pmp 600 cfm on a Cragar 471 Blower, but now am wondering if the fuel pump has gone bad. I took the pump apart to check for problems, but did not find any. Fuel pump used to come on with key turn, then stop at around 12 lbs until I started the engine. I even plugged the line from the pump to the primary, but it would not shut off. Any help would be greatly appreciated.
thanks, mike

If you have the pump wired through a relay you might want to check the relay as it could be sticking on or a bad ignition switch.

If your setup was working before, i would check for clogs or crimps in your lines. It almost sounds like your fuel is unable to return quick enough and its venting into the carb.

I had a similar problem with a electric fuel pump that works " On Demand". So if you have fuel pushing past needle valve in carb, it will empty the gas tank. I am running the mechanical pump and have the electric on a switch. I use it for starting and when I get vapor lock. Works great.....DAVE

I'm not sure how your car is set up. But if it is any thing like my set up then Junkyard Jeff called it right. You've got a bad Relay. My fuel pump did the same thing and it was a bad relay.


~ Vegas ~

I guess what I'm asking is what would you replace first? I'm now thinking new electric fuel pump. I thought about installing a pressure regulator, but even if that solves the problem, isn't the fuel pump still operating incorrectly? I mean, shouldn't it cease to push gas once correct pressure is reached prior to actually starting the engine? I don't really want to rebuild the carb if I don't have to.

I asked around a couple of Autoparts stores today for their help. I had previously thought I needed quite a bit of pressure because of 471 blower, but both stores told me because it basically a carbed motor, that's not neccessary.

thanks, mike

Where ever you have the little black square box's that plug in, is where you'll find the relay. Maybe in the fuse box. Do the relay first,it's the cheapest.


~ Vegas ~

One of you guys mention a relay problem, another is talking about a black box. This car was built around 1980 and is old school. The only wires I find are under the seat with only 2 fuses, and there are obviously those under the dash for the gauges and ignition. I realy don't know what I'm looking for here. Can anybody be a little more specific about wiring diagrams, or possibly point me in the direction of a book or publication, or even a website that is easily followed.
I did replace the fuel pump with a Holley red pump, and the pressure is around 6 now, but the pump is running upon key turn continously before cranking engine.

thanks, mike

Thats why I stuck with the mechanical pump. I was thinking of going with an electronic one but I keep hearing these stories where the pump would run all the time (car on or off)either due to bad relays or connecting to the wrong ignition wire.

I agree with everyone else. You either have a bad relay or connected it to a wire that is not hot on ignition.

Just wanted to post an update. I installed a Holley red pump, and readjusted the needle and seat on the primary. The pressure gauge shows a pretty constant 6psi, and so far the carb hasn't flooded the engine. I was a little concerned that the new pump runs continuously, but was told by a mechanic it's a rotor design with a bypass, so it's not pushing excess fuel. Seems to be running good so far. I still want to check into the wiring as you guys suggested just to be sure it's up to par.

Thanks to all those who replied,
mike

Some of the electric fuel pumps in the late 70,s would turn off when they reached 6-7 psi. No relays just a power wire to ignition switch and a ground wire.

You could just run your own switch in between the power and the pump. And turn it on when you go for a ride. Thought you would have figured this problem out by now. Have you checked out some of the other things the guys told you to check for?


~ Vegas ~

The fuel pump should not be running with the key off,it sounds like it is wired to the wrong side of the ignition switch. If there is power to the pump with the switch off then there is a problem so you will need to trace the wire from the pump and see where it is hooked up to and if its hooked to the battery side of the ignition switch you will need to hook it to the ignition or acsessory side or you might have a defective ignition switch also or someone hooked it to a constant hot wire. I ran a electric fuel pump on a 53 olds for many years and I had it hooked to the ignition post of the ignition switch and had no problems. Jeff

Maybe I was unclear. When I say the fuel pump runs continuously, I thought I stated in an earlier post that after key turned to on, but before cranking engine. The old fuel pump would come on at key turn, then come to a stop when it reached pressure before it went bad, pushing 15 to 20psi.
New pump seems to be doing fine.

mike

Sounds like you got it. My Bronco does the same thing when I turn the key on. Till it gets up to pressure, then shuts off,when it's not running. You should hear the thing when it's about to run out of gas. This happens every time my wife drives it, She has some thing about adding any gas to the tank. HE! HE! HE!


~ Vegas ~