Fuel pump question

Ant · #1 (**permalink**) 12-31-2012, 04:15 PM

Running a wide alloy foam filled tank, this tank is designed to have fuel lifted out of the top fittings on tank much like a lot of racing fuel cells. Pumping out of tank with a Holley red and a small back up pump so fuel can pumped from each side of tank, then to the fuel pot where an Aeromotive SS pump shoots the fuel to the bypass etc.

I read where Holley specify their pumps inlet/outlet should be level with bottom of the tank although I see a lot race cars etc pulling from the top, is it necessary to run non return valves etc?

Gaz64 · #2 (**permalink**) 12-31-2012, 07:30 PM

Mounting of the fuel pump (pump section) should be near level with bottom of fuel tank.

You still draw from the top, since the fuel will go up then down to the pump. Effectively functions the same as drawing from the bottom of the tank.

Once it has primed, it will stay primed. BUT drawing up then down makes the pump difficult to prime.
Don't let the pump try and prime itself, have a line off after the pump, and pressurise the tank (about 2-5 psi should do it).

Ant · #3 (**permalink**) 01-01-2013, 01:04 PM

Gary,

Thanks I guess its the fuel in the line going down to the pump that creates a vacuum each time to prime the system, the pump only needs a minute vacuum to work as a siphon.

Gaz64 · #4 (**permalink**) 01-01-2013, 01:23 PM

Quote:

Originally Posted by Ant

Gary,

Thanks I guess its the fuel in the line going down to the pump that creates a vacuum each time to prime the system, the pump only needs a minute vacuum to work as a siphon.

That's right, the inlet line will stay full and act as though the pump is pulling fuel directly from the bottom.

vector1 · #5 (**permalink**) 01-01-2013, 06:47 PM

i would think as long as there are no air leaks the pump would remain primed on top of the tank, but will have to pull fuel which i would think would be insignificant. with the pump at the bottom of the tank the siphon would provide fuel to the pump and not require the pump to pull.

Gaz64 · #6 (**permalink**) 01-02-2013, 03:18 AM

Quote:

Originally Posted by vector1

i would think as long as there are no air leaks the pump would remain primed on top of the tank, but will have to pull fuel which i would think would be insignificant. with the pump at the bottom of the tank the siphon would provide fuel to the pump and not require the pump to pull.

If you mount the pump above the tank, the fuel will drain back and the pump will have to self prime every time.

That's why you mount the pump near the bottom of the tank.

The fuel level will always be above the pump.

vector1 · #7 (**permalink**) 01-02-2013, 07:46 AM

Quote:

Originally Posted by Gaz64

If you mount the pump above the tank, the fuel will drain back and the pump will have to self prime every time.

That's why you mount the pump near the bottom of the tank.

The fuel level will always be above the pump.

so if the pump is below or at the bottom of the tank, does the portion of fuel in the line coming out of the tank drop back into the tank?

my point is the fluid doesn't know where the pump is, as long as there is no air leak, the siphon is maintained.

Gaz64 · #8 (**permalink**) 01-02-2013, 12:33 PM

Quote:

Originally Posted by vector1

so if the pump is below or at the bottom of the tank, does the portion of fuel in the line coming out of the tank drop back into the tank?

my point is the fluid doesn't know where the pump is, as long as there is no air leak, the siphon is maintained.

Yes, that would true to a point, but if the pump is higher than the level in the tank some of the fuel would still run back to the tank.

Better off with the pump at the bottom of the tank.