Fuel tank return, who needs it??

[graham]

Just finished installing and electric fuel pump. While fitting the pump it came with a return flow restrictor. I noticed the hole in the 'return' nipple on the fuel filter was almost blocked off. A lot smaller than the flow restrictor supplied with the pump. Checked an old filter I carry as a spare, found the same thing. Return hole almost completely blocked off. This appears to be the way these filters have been manufactured. Both filters had only a pin hole if that. Ryco made filters.
Let me to thinking (Dangerous territory :eek: ) what is the purpose of the fuel return? Will we survive without this feature? What could possiblely happen if this was comlpetely blocked off??

[xj2fsj]

I don't have an answer but I share your question. What are the potential hazards of a one way filter? And to add to that, When I finally get around to swapping the intake and 2bbl thats in there with an amc 4bbl intake and a 650 edelbrock will i need this feature?

[Chero77]

The fuel retun is supposed to eliminate any potential vapor lock problems and by all accounts it works well. The Fram fuel filters are properly designed and also work well. If you live in a hot climate, I would not remove this line. As an aside, any fuel injection setup you may one day install will require a fuel return line, so for that reason alone, I would suggest keeping the stock setup in place.

[Matthew W. Woodruff]

However small the hole for the return line may be, it does work, as the pool of gasoline on my intake manifold demonstrated before I replaced the leaking return line.

I would leave it be.

[710 Burner]

The return line also allows an escape for the pressure being produced by the pump when your carb. bowl is full. This extends the life of the fuel pump to oh, ..say just outside of town.

[Don S]

..
graham;

On PAGE 1J-1 and 1J-9 of the 1981 Jeep TSM “All (Jeep) vehicles
with six and eight cylinder engines have a fuel return system that
requires an extra nipple on the fuel filter to route fuel back to the fuel
tank. The filter must be installed with the return nipple upward”.

...NOTE... the return nipple is upward in order to bleed off the gasoline vapor first so it doesn't enter the carburetor and create problems there.

... ‘Some’ Jeeps also had a check-valve in the return line.
The fuel return line can help the fuel pump by removing vapor and
Engine heated gasoline from the pressure side of the pump. In some
cases the return line can reduce pressure spikes form the fuel pump.
Improper placement of the return line will eventually cause the fuel in
the tank to get very hot adding to the vapor lock problem. In a few cases
( by trial and error) the amount of fuel returned may need to be regulated
depending on the output, in gallons per minute of the fuel pump. The
line can be partially ‘pinched off’ with a small clamp or vise-grip.
… When using two or more fuel tanks hooking up the return line to the
tank you use the most… call it tank (A) would be the easiest. When you
are running on the other tank (B or C) some of the fuel is going to flow
into tank (A)… use a three nipple filter up close to the carburetor and the
little nipple up, facing the carburetor and hooked to the return line. Run
the return line in a safe place and away from high heat sources such as
the exhaust system.

Good Luck.. http://www.boylover.net/ubb/graemlins/cool_shades.gifand CUL.. Don S..

[graham]

:D Top Stuff one and all. you've talked me into leaving the return line intact. like the benifits of cool fuel circulating thru the system, especially with summer drawing near.
Next thing to work out is how much fuel should flow back to the tank. Suppose a few test with a pressure gauge should work out how much restriction is needed in the return line. Anyone know what pressure should be at the carby??

[Green Giant]

The Fram fuel filters are properly designed and also work well. SSSSHHHH.
Don't say that f-word here, it might set off a big debate. (I have been, and continue to use Fram for the last 25+ years w/o any problems.)

[graham]

Originally posted by Green Giant:
SSSHHHH. Don't say that f-word here, it might set off a big debate.Have I missed out....... again??

[Don S]

..
graham;
... According to my official 1981 Jeep TSM a fuel pump for a six cylinder engine should put out 4 to 5 psi and a fuel pump for an eight cylinder engine should put out 5 to 6.5 psi. Both six and eight cylinder fuel pumps should pump one pint in 30 seconds at idle RPM. These are ‘specs’ for 1981 Jeeps per AMC.

Fram Oil Filters Have taken alot of flack on the board here for being poor quality. http://www.feebleminds-gifs.com/smiley-faces-28.gif I don't use them now but have used alot of them in the past with no problems.

Lets ROCK !!! http://www.nagca.com/forum/images/smiles/1band.gif and CUL.. Don S..

[graham]

Originally posted by Don S:
..
graham... According to my official 1981 Jeep TSM a fuel pump for a six cylinder engine should put out 4 to 5 psi and a fuel pump for an eight cylinder engine should put out 5 to 6.5 psi. Both six and eight cylinder fuel pumps should pump one pint in 30 seconds at idle RPM. These are ‘specs’ for 1981 Jeeps per AMC.Don S..Haynes states 2.5 to 8 psi, but no indication of which engine. Flow rate same as your specs.
I'll measure fuel pressure and be happy with a result of 4 to 5 psi.