Fuel return changes?

[SASKCHEYENNE75]

Good afternoon,

I will be installing a used engine that I purchased into my 74 C20 as the original seized 350 turned out to be beyond repair. The used engine has a mechanical fuel pump with a return line however my current fuel system is not a return style. I plan on changing my fuel tank and fuel sending unit so should I just buy a tank/sending unit for a return style fuel system? Just making sure there are no other changes I need to make.

If my fuel tank was good I likely would've just swapped to a different fuel pump but since I have to switch the tank anyhow I might as well get a return style.

 

[Broken85]

Probably need to tell us what your current system actually is. Is it mechanical also? Is it fuel injected?? Internal pumps??

 

[Ricko1966]

Good afternoon,

I will be installing a used engine that I purchased into my 74 C20 as the original seized 350 turned out to be beyond repair. The used engine has a mechanical fuel pump with a return line however my current fuel system is not a return style. I plan on changing my fuel tank and fuel sending unit so should I just buy a tank/sending unit for a return style fuel system? Just making sure there are no other changes I need to make.

If my fuel tank was good I likely would've just swapped to a different fuel pump but since I have to switch the tank anyhow I might as well get a return style.

Yes just buy a 3 port sender and bend up a return line from steel tubing available at the local parts store. Alternatively you could just swap your old pump on to your new motor. The return style is extra insurance against vapor lock. No matter what you do now when replacing the sender buy the 3 port to have the most options in the future use short links of hose with bolts in them to cap unused ports for now.

 

[Moodyalaskan]

Maybe swap in your old fuel pump.

 

[SASKCHEYENNE75]

Probably need to tell us what your current system actually is. Is it mechanical also? Is it fuel injected?? Internal pumps??

My current system is the factory tank with no return line and a factory style mechanical fuel pump

 

[SASKCHEYENNE75]

Maybe swap in your old fuel pump.

Thats what I was going to do but need to replace the tank and fuel sending unit anyhow as well

 

[Radiohead]

If I remember correctly, the tanks (regardless of size) were androgynous but the sending units are side and year specific. LMC has wonderful illustrations to help visualize the shapes and placement of things.

 

[75gmck25]

A 3 port sending unit has ports for fuel feed to engine, fuel return from pump, and vapor line to canister under the hood.

Fuel return line is a good idea to prevent vapor lock, but if you have dual tanks then you then need a 6 port solenoid.

A ‘74 350 may have had a vented gas cap and no vapor recovery canister. However, my ‘75 K25 with 350 has both a fuel return line and a vapor canister, so you never know.

 

[Turbo4whl]

If my fuel tank was good I likely would've just swapped to a different fuel pump but since I have to switch the tank anyhow I might as well get a return style.

I will be installing a used engine that I purchased into my 74 C20

1974, as you know does not have a fuel return, does not need one. Would be necessary if you are not running a carburetor and have fuel injection.

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See the small hole on the top of the pump, that is the diaphragm vent. Allows the diaphragm to move freely, vented to atmosphere.

Old fuel pump, diaphragm cracks, fuel comes out the vent. EPA wanted no fuel leaking. Move the diaphragm vent to the bottom, add a hose back to the tank as a vent. No fuel gets out, EPA is happy. Not a fuel return. Use the correct fuel pump, don't need to change anything else.