electric fuel pump wiring

Look in the Electrical section of my web site for one method. This circuit ensures that the pump won't keep running after the engine dies (like in an accident).

I understand that "modern" cars use an inertia or impact-sensing switch to cut off the pump. Ask at any auto parts store.

Speedy Jim

You're correct; the electric fuel pump should be tapped off the ignition circuit. The positive side of the ignition coil already feeds the backup light circuit. That would be one option for a connection point. You'd need some kind of fuse, of course.

There's one more thing to consider with an electric fuel pump. Safety devices are available that will shut the fuel pump off in the event of an accident. They are generally called inertia switches. Some of those fuel pumps are capable of pumping a lot of volume (you are running a fuel regulator, right?). So if you're involved in an accident and a fuel line is ruptured, the pump keeps dumping fuel out.... and suddenly you've got a potential gas fire. So this little gadget senses when it's either not right side up, or when there's been a serious impact in any direction, and pops like a circuit breaker, turning the pump off.

The last time I saw one available in an aftermarket version was in a Moss Motors MGB catalog. They were about $60, but peace of mind is a wonderful thing. If you ask at your local NAPA store, I'd bet they could also get you one. If I were going to rig up an electric pump, I'd go to a wrecking yard and nab an inertia switch out of a Ford Escort. They put them behind a marked panel in the trunk, and they just sit there, protecting you. The only thing about them is they can trigger if you were to, say, run over a

4x4 or a big rock or something that really bumps the car hard. Then your engine quits and you have to go press the little pop-up button to turn the pump back on. False triggers are very rare; every fuel-injected car on the road has one of these gadgets in it, and they work very well.

Cheers, Walt

Thanks I'll check it out. I built my vehicle from a rusted heap of a 69 Ghia. Popped in a super beetle transaxle and my old bus engine (Type IV) and I'm about one half day from attempting a startup.

-mike

Yea, I was thinking that the coil might be a good place to hook up the pump. I plan to put in an in-line fuse. I am not using a regulator. I may purchase one this week though. The pump I got is rated at 2.5 - 4.5 pounds. It was the pump actually suggested in the autozone computer. (As if that really means anything) I'm excited. One more day and I hope to start her up. Thanks, Mike

Borrow a fuel pump relay from an early fuel-injected Golf.

These have a coil input so that when the engine stops turning, the fuel pump shuts off in a second.

The relay supplies power directly from the battery, via a fuse of course. Control is via the "ignition-on" connector which allows the pump to run for about 2 seconds at initial switch-on even without the engine turning.