Fuel pump question..... Not a GMT400 but still GM.

[Erik the Awful]

The cheapest sending unit on RockAuto...

More Information for BRUTE POWER 1070003

... plus the cheapest Vortec fuel pump on RockAuto... (Note that these might not be the same brands I used, it was three years ago)

More Information for US MOTOR WORKS USEP3240R

The Vortec fuel pump is an exact fit replacement for the TBI pump.

 

[DeCaff2007]

I have solved the problem.

The Buick was never equipped with a fuel return line. The 2GC EFI conversion has a fitting for a return line. However, the EFI fuel pump (while a retrofit for the factory tank) does NOT have a return line, so I simply capped off the fitting on the 2GC unit. This caused a problem, putting the fuel pressure over 100 psi.

So, first I took my fuel pressure gauge OFF the Buick and installed it quickly on my Silverado, just to verify a working gauge. It held at 58 psi no problem. Ok, the gauge is good.

Then, just for sh1ts and giggles, I took the cap off the return line on the 2GC EFI unit, and rigged a hose from that into a bucket. Wife turns the key to run and BAM - 58 psi (but quickly falling) because there was no way to regulate an open hose into a bucket lol. If that line were in the tank, the pressure would stay constant.

There's no such thing as an EFI retrofit fuel pump WITH return line, for THAT VEHICLE. Have to either buy a whole new EFI tank with an aftermarket EFI pump, or, get creative with the existing EFI pump.

Stay tuned. I WILL get this working.

 

[GoToGuy]

You have a project that appears you really didn't research or read the install.
Do you know how to plumb a return fuel line?
Does it need a check valve?
Was this project beyond your ability and or skill level?
Most relays will still function with 9.5 - 10 Volt's.
Did the Holly system state what fuel pump specs and routing was required?
I have not installed a Holly system but the ones I have worked on were very specific and informative. When working with fuel, the law of " unintended consequences" can bite you faster than the speed of light.
Why would any carbed ' pre smog, pre injection vehicles have a fuel return, that's a given.

 

[Schurkey]

Why would any carbed ' pre smog, pre injection vehicles have a fuel return, that's a given.

Almost universal on cars equipped with A/C. As the popularity of air conditioning increased, so did the percentage of vehicles with a fuel return system.

The "return" on those vehicles is heavily restricted--a small orifice in the fuel pump return nipple--intended to pass fuel vapor but not much liquid fuel. The plumbing back to the tank was usually 1/4" hose/tubing.

The point was to reduce vapor-lock of the engine-driven fuel pump. Worked pretty well. Entirely unsuitable as a fuel-return system for a return-style pressure regulator--the 1/4" tubing is too small.





You have a fuel-return fitting on the throttle body. Determine the size of the nipple. Route some tubing (and short sections of hose to connect to the engine and to the tank) the same size to the tank area of the car. Punch a hole in the "new" fuel sending unit, solder-in a new elbow/nipple of the correct size, with enough metal tubing inside the tank so that the returned fuel doesn't interfere with the sending-unit float.

How can the Holley have a fuel-pressure regulator in the tank, if blocking the fuel return at the throttle body results in excess pressure? I think you've been lied-to.

 

[DeCaff2007]

Almost universal on cars equipped with A/C. As the popularity of air conditioning increased, so did the percentage of vehicles with a fuel return system.

The "return" on those vehicles is heavily restricted--a small orifice in the fuel pump return nipple--intended to pass fuel vapor but not much liquid fuel. The plumbing back to the tank was usually 1/4" hose/tubing.

The point was to reduce vapor-lock of the engine-driven fuel pump. Worked pretty well. Entirely unsuitable as a fuel-return system for a return-style pressure regulator--the 1/4" tubing is too small.





You have a fuel-return fitting on the throttle body. Determine the size of the nipple. Route some tubing (and short sections of hose to connect to the engine and to the tank) the same size to the tank area of the car. Punch a hole in the "new" fuel sending unit, solder-in a new elbow/nipple of the correct size, with enough metal tubing inside the tank so that the returned fuel doesn't interfere with the sending-unit float.

How can the Holley have a fuel-pressure regulator in the tank, if blocking the fuel return at the throttle body results in excess pressure? I think you've been lied-to.

Solder? I didn't know you can solder fittings onto a fuel pump. I can *absolutely* do that. I also wish I would have know that before I went using a step bit to make a hole big enough to thread a 3/8 NPT fitting into the fuel pump. That really did nothing more than make a mess, but this is what happens when trying to save time and money by using parts that are on hand.... as opposed to waiting a week for Amazon to ship things..... because the auto parts stores around here absolute ****.

OH, and btw, the return line on the 2GC EFI does not have a traditional fitting. It's threaded for 6AN, then you just order a fitting for whatever you are plumbing to. In this case, it'll be a 3/8ths EFI rubber hose (then of course steel tube after that).