sportybry

Hey guys-

I'm running a Carter P4070 (6psi) electric 72GPH fuel pump. I've already run the supply line in my project, but I'm wondering if I need or should add a return line as well? It will be a bit tricky to run one, plus I'll have to modify my in tank fuel pickup to add a return-line fitting to it

Does anyone here have experience with the particular pump I'm using?


Engine is a carb'd 302 running around 370-400HPish. Car will be 90% street driven, with the occasional lapping day and 1/4 mile fun.


I've been told that:

1) a return line will improve reliability. However, I'm not sure if that's true? The Carter is a rotary vane pump and most aftermarket ones are of a different design that is -perhaps- more sensitive to backpressure?

2) a return line will make my fuel cooler. Again I don't know if this is true -- doesn't that carter have an internal pressure regulator that will simply cycle fuel within the pump (as opposed to drawing more from the tank) if it's seeing more than 6psi of restriction downline? Why would this heat the fuel extensively?

3) a return line will make my pump run quieter. Again, not sure this is true given the type of Carter pump I have? If the bypass activates doesn't this alleviate backpressure on the pump? so why would it be louder? As for NVH, I've already double insulated the pump with rubber mounts: frame-to-bracket AND bracket-to-pump.


I'd like to hear from other people, and their experience/thoughts? If your experience is with another brand of pump though, PLEASE state which make it was.


- Brian

ZZmustang

Depends on your fuel pump
Does it shut off when a certain pressure is met? Is it adjustable?
color of plugs, (to rich/lean) does your engine need 6psi?
size of fuel line?

Depends on a bunch of things.
If your idling and the pump shuts off then the need for a return line is not there.
if your idling and the pump is constantly running, then your using more fuel than you pump can put out if it has a shut off on it.
Try this, disconnect the fuel line to your carb and block the fuel line with a bolt or something and turn on the pump. if it builds pressure and shuts off, no return line. if it keeps running it needs a return line cause its just using its internal bypass.

By the way, getting a fuel pump that shuts off is much easier that a return line.

sportybry

Thanks for the reply ZZ. My project is still under construction, so it hasn't hit the road and the engine hasn't been run -- so I don't know the answer to some of your questions.

- the fuel line is 3/8" diameter
- fuel pump pressure is not adjustable

What are some well known fuel pumps that "shut off" ? Does anyone know if my Carter is one of these? I've asked Carter for tech info, but they say they don't deal direct with consumers. Well, that's just great, isn't it?

- Brian

Colorado_Mustang

Take a look at your post in the General section. I'm not typing that twice...[>:]