Nice write up and job. Thanks for sharing.
I wonder if an inertia switch from a Crown Vic or Grand Marquis would work? I've taken out a few from Demo Derby cars.
Reps

 

I think pretty much any one wired in correctly should work.

 

Thanks again guys.

If I were to add an inertia switch, a vehicle like that is probably where I'd start looking. I didn't do a whole lot of research, but the ones I did find during a first pass where for Ford applications. I'd need to investigate how the switches are set up, but if they're a simple SPST switch (almost like a circuit breaker), I'd set it up to interrupt the ground path of the relay coil. I left that part of the wiring easy to modify if I so choose.

 

Excellent installation post.
I have be thinking about doing a similar install, but using it as a fuel primer application with a momentary switch.

That being said. Do you know if I could retain my current mechanical fuel pump and add an electrical pump set up?
Will the mechanical pump allow the electrical pump to push fuel through it? And visa versa, will the electrical pump allow the mechanical pump to pull fuel through it with no problems?

Thank you

 

Your best bet is to have isolation valves so they don't interfere with each other. One thing to consider is that your mechanical pump will run regardless of fuel supply.

 

Thanks for the kind words.

I've heard of folks using an electric fuel pump in combination with the existing mechanical pump, but I don't totally understand how that setup works, nor do I really see the point. With the electric pump in place, there's no need for a mechanical pump. When installed correctly, the pump is capable of pushing fuel all the way from the tank up to the engine on its own. My motivation, as is often the case, was to actually eliminate the mechanical pump altogether. To do this conversion and still retain the mechanical pump would be counter-productive.

I would be curious if there exists a concern that the setup you describe would stress either pump in some fashion - like I said, it's not a concept that I understand. Also note that the "priming" function you describe is not necessary. The Hobbs switch allows the pump to run in the absence of built-up oil pressure with the key in START and the engine cranking. In my experience, the electric pump can move fuel to the carburetor surprisingly fast, and the engine cranking is more than enough time to prime the pump. As such, the act of cranking the engine is what primes the pump, and it happens so quickly it seems, that you hardly even notice what's happening. However, it would be very easy to add this setup with a momentary switch if necessary.

My intent is not for this thread to turn into a discussion of fluid mechanics or fuel pump theory, but I don't understand this statement. An electric fuel pump will continue to run too as fuel runs out, just like a mechanical pump (until the engine cuts off). Neither has any sense of the fuel supply upstream.

 

With that being said, It does not seem practical to have both.

If I am going to resolve my priming issue with an electric fuel pump, I might as well dedicate it as the fuel supply system.

Thanks for the insight.

 

Years ago a guy I knew was having mechanical pump problems. He wanted the look of the fuel pump on the engine, so he eliminated the actuating arm, removed the valves, made a plate/gaskets for the engine mounting side and for the place where the diaphragm was. Benefits of electric, looks of a mechanical.

 

FMC

Would you please explain how you wired the three terminals on the Hobbs switch.

From what I can tell, one terminal is for 12 volts signal for the windings in the relay. Is another one N.O for oil pressure? Is one NC for the cranking voltage?

Thank you

 

That's the idea. The switch has three terminals: P, S, and I. P is for the pump relay coil, S is hot-in-START, and I is hot-in-RUN. P is connected to S when there is no oil pressure. After there is enough oil pressure, P is disconnected from S and connected to I. It is essentially an SPDT switch.

 

I have been running electric fuel pumps for over twenty years. I always had trouble with the mechanical pumps leaking oil and not delivering enough fuel during long hard pulls while towing. I got tired of the oil mess and the fuel starvation so I changed over to the Mallory 110 electric pumps and a Holley fuel pressure regulator. I got rid of the old plumbing and ran a fuel line from the regulator straight up the firewall to a homemade fuel rail. I run two pumps in parallel. If one breaks down I can just flip a switch and keep going on the backup pump. You would understand the importance of this if you have ever had had the pump fail during the middle of the night during an electrical storm a 100 miles from nowhere and 600 miles from home.

 

Fmc, I was wondering what did you use for your ignition source? I have a similar set up but right now and the pump turns on only when engine has oil pressure, I've got my ignition source running off the ignition modules red wire which leads too the fuel pump relay, but I've heard this is wrong and can cause problems. I've read that it should be wired into the ignition switch but I'm not sure on how to do this.

 

See your other thread.

 

Great work on this!
I know this is an older post but I've kept it subscribed and now it's time to do my own, ordered a Carter pump p4070, Hobbs switch, relay, and block off plate.
I'm hoping to eliminate vapor lock and a lack of fuel pressure I have since installing an edelbrock 1826 650cfm carb, intake, and regulator setup. Hasn't ran right since the install. Even had a bad float out of the box.

But my main question is have you had any issues with where you mounted the pump, being further away from the tank. I know you did this on a 2wd.
Mine will be on a 4x4 mainly off road truck. My other question is for your ignition hot wiring did you run all the way in the cab or use another circuit for that?

 

No OP, but maybe I can help.
I used a OE fuel pump and tank from a 90's truck. High pressure fuel can push a long way! If your having problems with vapour lock, and are trying this setup then mount the Fuel regulator close to the carb away from heat sources. I used a Holly 12-803BP By-Pass Regulator when I was transitioning from carb to efi. The Holley 12-803BP looks the same as the regulator in a photo above.

As for wiring the fuel pumps, I used a couple of relays. One was switching front/rear tanks (Dual tanks), and the other was to turn on fused battery power on/off when the ignition was switched on and on start. One snafu was that I had to use two wires to keep the relay switched on. I used the plug going to the Ford Duraspark ICM module. And Diodes and a relay... and complicated things. :L Anyway, here's the post I made: https://www.ford-trucks.com/forums/1...l#post15487092