86 C10 454 . Help with fuel return line. Pic's inside.

[Nasty-LSX]

Ok, so on the 454 swap C10, I needed to put a electric fuel pump because the 99 Vortec does not have a mechanical fuel pump.
I had a Holley blue pump (14PSI) and used it. I also used a none bypass regulator. (bad idea) So now I am revamping it correctly.
I am still using the Holley blue pump but bought a BP regulator.(holley). I put a 100 micron filter behind the pump and a 40 micron
filter in front of it. (rear by tank) So up front when the 305 was in it, there is a 3/8 feed for the fuel and a 5 1/6 for the return fuel line.
I used the 3/8 to feed through the regulator and used the 5 1/6 return line as the bypass line.

Here is the problem. I think the 5 1/6 line is to small. When the pump is on, my fuel gauge maxes out and fuel comes out the carb over flowing. I thought I had a bad regulator, so I removed the Bypass hose(return line) and turned the pump on. Then it was at 6 PSI. So
I need a larger return line? Here is a good question, the fuel valve that switches the tanks, Could that be the issue? That 5 1/6 line goes right into it. There is a line that looks like a 3/8 line that runs to the charcoal canister. Can I use that as a return line?

here is the top side

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[Nasty-LSX]

here is the tank switch, the T were my finger is, is the vent tubes for the charcoal canister up front
then you can see the left and right side lines for each tank.

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[Nasty-LSX]

here is the pump set up! and tiny 5 1/6th return line that goes into that switch.

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pretty tiny return line here

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[Nasty-LSX]

Could it be the fuel is not pushing through the tanks switch valve?

I dont mind using only one side of a tank is I have to . I need this BP to work correctly.

 

[SquareRoot]

I'm using a similar setup with EFI. 5/16 return with a 3/8 feed is not a problem. On EFI, according to Aeromotive, the correct way is to have the regulator AFTER the carb/ fuel rail on the return line. Don't know if this helps in your case.

 

[SquareRoot]

Could it be the fuel is not pushing through the tanks switch valve?

I dont mind using only one side of a tank is I have to . I need this BP to work correctly.

This sounds likely.

 

[Bextreme04]

I agree, 5/16" is completely sufficient for a return line. I would suggest trying to blow through the return line and see if it is able to free flow back to the tank. My vent lines are 1/4", I don't think I have ever seen 3/8" vent. I wonder if you have the vent line and return lines swapped? The vent line should be smaller than the return.

 

[hogdaddy]

I'm using a similar setup with EFI. 5/16 return with a 3/8 feed is not a problem. On EFI, according to Aeromotive, the correct way is to have the regulator AFTER the carb/ fuel rail on the return line. Don't know if this helps in your case.

I believe that only applies to EFI. This was included in my Aeromotive kit instructions. I have this kit:
https://aeromotiveinc.com/product/carbureted-phantom-200-kit/
Here's a diagram included in instructions.
Notice supply and return line is same size and regulator BEFORE the carb.

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[nvrenuf]

I run an OE TBI pump with a return style regulator and I've never had a backpressure issue with the original 5/16 return line. I'd pull the return hose off of the dual tank valve and dump it into a gas can then see what kind of pressure you have. I'd bet you're plugged up somewhere in the old parts.

My set up runs rock solid 6 psi all day:

OE in tank TBI pump > 3/8 feed > OE fuel filter > QJET > Holley bypass regulator > 5/16 return.

I also have 1 pressure gauge at the carb and 1 in the dash, having a gauge while driving is great for diagnosis.

 

[Nasty-LSX]

I wonder if you have the vent line and return lines swapped? The vent line should be smaller than the return.

Everything is plummed correctly. I have the 3/8 for fuel
and have the return and vent line. The vent line that runs
to the charcoal canister is larger than the return line. Thats why I was wondering if I could use the vent line as a return line since it was bigger. Im going to run air through the return line and see what happens. I will disconnect right before the fuel tank switch valve.

 

[Nasty-LSX]

This sounds likely.

Yea, when everything is hooked up(correctly) And I turn on the pump, I can see my fuel hose expand like the return line is not flowing. Thats why I was thinking the tank switch valve was not letting it pass through the valve. Might not be able to use high pressure for a return through the valve switch. Well not high pressure. but 8lbs. Pump is 14 PSI and regulator is set at 6 PSI

 

[SquareRoot]

Yea, when everything is hooked up(correctly) And I turn on the pump, I can see my fuel hose expand like the return line is not flowing. Thats why I was thinking the tank switch valve was not letting it pass through the valve. Might not be able to use high pressure for a return through the valve switch. Well not high pressure. but 8lbs. Pump is 14 PSI and regulator is set at 6 PSI

I'm pushing 43 psi thru mine. Pollack 6 port without issue. 87 tbi units they were factory.

 

[Nasty-LSX]

I'm pushing 43 psi thru mine. Pollack 6 port without issue. 87 tbi units they were factory.

Mine is 86 non EFI. Im guessing the tank switch wont
take pressure being they were made for mechanical pumps

 

[Nasty-LSX]

ok this is the regulator I got.


https://www.holley.com/products/fue...regulators/carbureted_regulators/parts/12-887

 

[nvrenuf]

I’m using a 12-841.