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

[Nasty-LSX]

here is a update. I followed the 1/4 return line all the way from front to back. There is no kink,bends or
damage to the line. I blew air through it and its clear. I unhooked it from the fuel switch. I reconnected
the return line at the regulator and left the hose disconnected at the rear tank valve. turn the pump on
and yup, gas goes through the line like it suppose to.

Here is the problem. The pressure still spikes high and you can see the fuel line to the carb bulge. I tried to readjust
the regulator and it makes no difference. Could I have a bad regulator?? I thought if it was set a 6PSI then thats all
it would put out to the carb. Ill call holley monday. Does not seem right. I get 6psi as long as the return hose is
unplugged at the regulator

 

[Nasty-LSX]

I’m using a 12-841.

Thats a BAD@SS regulator.

 

[hogdaddy]

I don't know if it makes a difference but Holley's instructions for your regulator has the filters before the regulator.
The reviews on your regulator on Summit are mixed good/bad.

Holley 12-887 Holley Carburetor Bypass Style Fuel Pressure Regulators | Summit Racing

Free Shipping - Holley Carburetor Bypass Style Fuel Pressure Regulators with qualifying orders of $109. Shop Fuel Pressure Regulators at Summit Racing.

www.summitracing.com

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That regulator can be after the carb also it says.

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[hogdaddy]

The stock mechanical fuel pump on my 86 truck had 3 lines also. 3/8" supply, 1/4" return and 5/16" cannister vent line. Are you sure your return is 5/16"?
1/4" would be too small for proper return line with an electric pump.
I am using aftermarket braided PTFE lines now as I took all the other 3 stock steel lines out.

 

[nvrenuf]

Thats a BAD@SS regulator.

Thanks. I never trusted the style that comes with the blue pumps after a local speed shop guy told me some racers used to run 2 back to back because 1 couldn’t always manage the pressure.

 

[Nasty-LSX]

I don't know if it makes a difference but Holley's instructions for your regulator has the filters before the regulator.
The reviews on your regulator on Summit are mixed good/bad.

Holley 12-887 Holley Carburetor Bypass Style Fuel Pressure Regulators | Summit Racing

Free Shipping - Holley Carburetor Bypass Style Fuel Pressure Regulators with qualifying orders of $109. Shop Fuel Pressure Regulators at Summit Racing.

www.summitracing.com

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That regulator can be after the carb also it says.

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Thanks HogDaddy. I am using figure #2 setup exactly. Then I have a filter before the carb just because I had an extra!

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[Nasty-LSX]

The stock mechanical fuel pump on my 86 truck had 3 lines also. 3/8" supply, 1/4" return and 5/16" cannister vent line. Are you sure your return is 5/16"?
1/4" would be too small for proper return line with an electric pump.
I am using aftermarket braided PTFE lines now as I took all the other 3 stock steel lines out.

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I only have 2 lines coming out by where the mechanical fuel pump use to be. 3/8 and 1/4
the the bigger 5/16 line runs to the canister

 

[Nasty-LSX]

then the canister. My finger is pointing to the rubber, second pic shows the larger 5/16 steel line.

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[Nasty-LSX]

Im thinking I could just buy a vented cap and use the one tank by using the vented line as a return.
I know I could just buy a Red holley 6PSI pump ($180) but why when I already got this set up. Need to
just make it work correctly

 

[Nasty-LSX]

Im a dumbA@@. I been saying the size wrong this whole time.

Hogdaddy is correct on size i been saying it backward. (3/8" supply, 1/4" return and 5/16" cannister)

So yea, the 1/4 line must be to small for a return.

 

[Turbo4whl]

Okay, about that small line on the mechanical fuel pump. Early pumps had fuel in, fuel out and a vent for the back side of the pump diaphragm. (small hole in the case) EPA wanted no leaking diaphragms pushing fuel out so, the mechanical pumps on later squares had the third line for the vent. This vent line was hooked to the tank on some units and to the charcoal can on others.

That line was not used as a fuel return ever on a mechanical pump. Mechanical pumps have no dedicated fuel return, just a contained vent. In some cases this could be used as a fuel return if it goes to the tank.

 

[Nasty-LSX]

In some cases this could be used as a fuel return if it goes to the tank.

Yup mine does. Thats why I was thinking I could use it. I would be stuck using one tank but thats ok with me. Im
sure I would need a vented gas cap also

 

[hogdaddy]

Yup mine does. Thats why I was thinking I could use it. I would be stuck using one tank but thats ok with me. Im
sure I would need a vented gas cap also

Turbo4whl is correct on the third line, I just referred to it as a return line.
.
I use this for a vent instead of the cannister. A vented gas cap would not be best imho.
The holley has a safety feature in case of rollover

Holley Sniper EFI 19-174 Remote Mount Vent Valve for EFI Fuel Tanks

Remote Mount Vent Valve for EFI Fuel Tanks- Barb size is 5/16".

www.holley.com

 

[Nasty-LSX]

Well it dont matter what I do. I used the 5/16 vent line as a return and it does the exact same thing
I even blew through the tank switch and it was easy to blow through into the tank. Im guessing
a BAD regulator. I might just go ahead and pick up a red pump. Do it right and dont look back.
If I get the red pump i can keep both tanks as i need no regulator. Pump is set to 6PSI

 

[hogdaddy]

Which fuel pump & carb do you have now and do I see 3 fuel filters?