Greetings all,

I have a 460 in my 78 f150 4x4, and the PO removed the mechanical fuel pump and installed a Carter electric pump under the hood. I've been told by many that the pump should push the gas and not pull it, so I mounted it back by the tank. It works great and I'm having no problems with it.

My concern is that it's a one-speed on-or-off pump so it's always running when the key is on. There's no pressure activated shut-off so it just keeps pumping even when the engine isn't running. Shouldn't there be some kind of valve or shut-off? Am I gonna have problems with my rubber gas line brusting from the pressure or am I just being paraniod?

Any suggestions for improving my setup?

Thanks in advance!

Kevin K.

 

You should be fine but there are several versions of that pump.

5psi and 8psi self regulating (internal bypass) and a 15psi that should be used with a return line and bypass regulator or at least a standard regulator.

I do carry a spare.

 

Will it say the PSI on the pump and weather or not it's self-regulated? I'll have to look at it tonight. I know I don't have a return line.

Thanks for the reply!

Kevin K.

 

Look for the part number on the pump and then compare it to the Summit racing site parts. I think the 8psi is a P4070 but don't remember for sure.

 

kojak, I installed a Holley "blue" electric pump on my 77, f250. 0 to 15 psi. I have an in cab tank so i mounted the pump on the outside frame rail direcly below the tank. ran it for a couple of months with no return line. finally , i ran a return line from the input side of the regulator back to the tank via a 1\4 inch hole drilled thru the round part of the sending unit. the reason i mention this is that the pump is able to COOL itself by constantly being able to circulate a portion of the total fuel volume back to the tank. I have my regulator set at 7 psi so as not to over-pressurize the float in the carb. From the output side of the regulator i run a 3\8 inch fuel line up to the carb. Also , I use 3\8's inch , clear fuel filters on the suction and pressure side of the fuel pump. I also have a 0 to 15 psi inline pressure gauge from Summit that is really a must in my opinion. fd

 

You could always install a oil pressure actuated switch for the fuel pump.This device Tee's into the Oil Sending unit pipe.

This is the safest way to go if you are doing electric.

As you are turning the engine over the oil pressure increase causes the switch to *ground out* > turning the pump on.
If you are in an accident, the lack of oil pressure if the engine dies <> will shut the fuel pump off.

Safety counts

 

Very good idea guys. I like to wire in an oil pressure switch also. Another thing that is good is a "hot in start" power line to the pump. Without this function you will have hard start problems if the vehicle has been setting for a while and the gas in the carb is gone.

The pump will get very hot just bypassing fuel from the output side thru the pressure relief back to the inlet. The bypass regulator or a fixed orifice bypass is a good idea. Not only will this keep the pump cool it will prevent vapor lock if the bypass reg or orifice is up near the carb inlet. The carb will always be getting nice cool fuel.

 

First post in this forum from a lifetime Chevy owner and "new" 79 F-150 owner. This is a great source of info.

I do a lot of aftermarket stuff and would offer the following suggestions for whatever it's worth ...

1. Electric pumps are much better at pushing fuel, not pulling it. Get rid of the underhood location. They are designed to be mounted as close to the tank as possible, preferably a bit below it so the fuel can almost siphon out to the pump. Also, try to place the pump so that it gets some airflow - they get pretty hot as they run.

2. Use a relay for the pump rather than running the power voltage for the pump thru a switch. This way, the pump gets more direct voltage (switch = resistance). 12v power lead to relay and from relay to pump should be 10-12 ga, switch power wire can be 16 ga - it just takes milliamps to activate a relay. I use auto reset circuit breakers for electric pumps - if there is an overload for some reason the circuit breaker will break the connection, then re-connect as it cools. No fuse to remove/install.

3. Check the fuel line diameter - all the way to the tank pickup. A 3/8" line does little good if the tank pickup tube is too small. I use 1/2" line for any engines over 400 ci. Going from 3/8" to 1/2" line usually increase fuel pressure at the carb by 1 psi so it does make a difference. The majority of applications work well with 3/8" line though.

4. Use a pressure regulator and a fuel pressure gauge mounted in the engine compartment - the inexpensive ones that Summit/Jegs sell work just fine. Holley carbs seem to like about 5-6 psi at the bowls, Carter/Edelbrock/Q-Jet can go as high as 7 psi without a lot of fuss.

5. I like Mallory pumps - they are quiet and last a long time. I use the Comp 110 for applications to about 300-350 hp. then the Comp 140 for higher hp. The Comp 100 does not need a fuel return line, but the Comp 140 does.

6. I wire the pump power lead to a constant 12v source (not ignition controlled). Reason for this is that I use a DPDT (double pole, double throw) switch to control the pump. Middle position of switch = everything off. Down position = pump bypass = pump is manually switched on to prime carb. Up position = pump on but controlled thru oil pressure safety switch. Starting procedure means I flip the switch down to prime the carb, then flip it up before starting the car. I also wire in indicator lamps to let me know if the pump is in manual or automatic mode.

7. ALWAYS use an oil pressure safety switch. Never let a pump run without some type of control in case the engine shuts down. No exceptions!

8. Use as little of the regular auto parts rubber fuel line as you can. I like the Aeroquip blue hose or steel line for the long runs, then I use braided line/fittings from regulator to carb. For carbs with front/rear bowls I run a separate line from each side of the regulator to each bowl.

9. Install a good filter between tank and fuel pump. This keeps trash out of both pump and carb. I do this for mechanical pumps too.

Sorry to get long-winded here. Might sound like a lot of overkill on the fuel system, but I have found that this setup works very dependably for a long time. That equals peace of mind when you're a long way from home!

 

Thank you all for the excellent suggestions.

The only number I could see on the pump is 40706F20A. I'm assuming that's the 4070 pump and that the 20A means 20 amps. The website I checked says the pumps only draw 3 amps so I'm not too concerned about the relay setup. I may add one anyways, though. I couldn't find anything that said whether or not it's self regulating either.

When I moved the pump back to the tank, I rewired it. The P/O had it wired up REALLY hokey. When I connected some of the wires he cut off, the fuel pump went on when I pushed the windshield washer switch. That was funny!

On my fuse box in the upper left corner was a slot marked AUX FUEL or something like that. There was only one half of the fuse socket so I assumed it wasn't used for this model. I wired my fuel pump to that (with an inline fuse of course). Anyone know what that fuse is supposed to be for?

Thanks again all!

Kevin K.