Holley In-tank Fuel Pump Issue

[Snakerake]

Hey all,

Has anyone around here installed one of these? 350 LPH Module 1973-1991 Blazer/Jimmy (31 Gallon)

I'm installing a sniper efi and one of these fuel pump/sending units and I'm very confused over which line goes where. On the OEM sending unit I removed, the 3/8 line is fuel, the 5/16 line is Vapor (to Charcoal Canister), and the 1/4" line is the return.

On this new unit it seems the Vapor and Return lines are swapped - with what appears to be the return line as 5/16 and the Vapor line as 1/4.

Am I crazy? It doesn't seem like the vapor line should run down to the bottom of the tank.

I made a side by side image with the old and new unit. Anyone with some experience or knowledge here, please take a look. What am I missing?

 

[Kain]

no the return should run to the bottom so it dont make the float do funny things.The vent line is just for vapors.

 

[pblaze725]

The sniper efi system recommends a 3/8” return line.

See page 10 of 76

https://documents.holley.com/199r11031r.pdf

 

[Snakerake]

The sniper efi system recommends a 3/8” return line.

See page 10 of 76

https://documents.holley.com/199r11031r.pdf

Thanks for this - Seeing this got me to call Holley - because the 5/16 return made even less sense then. The guy said they swapped the lines since 1/4 line is too narrow for the EFI return and that the 5/16 hard line is sufficient for the return line. I guess I've got some rerouting to do in the engine bay.

 

[pblaze725]

You CAN run a 5/16 return line but it could cause issues with back pressure creating a rich condition making the CPU constantly trying to compensate for it.
You want a constant even flow coming from the tank and returning back.

I have no issue with that sending unit 5/16 return line dropping down to the bottom of the tank. The idea is that the fuel is dropped off right next to where it gets picked up.
The 1/4” vent should be at the top, that’s where all the vapors are.

My only issue is that it’s not set up for 3/8” return.

I have modified sending units like that by removing the 5/16 line & soldering in a 3/8 one.

 

[sweetk30]

the 500 miles of hell i had with my sniper on a 5/16 line had no problems .

and you pulled a carbbed sender and now installing a efi sender so unless you swapped the tank for a efi unit with the baffle keep it a min 1/4tank of fuel or you might have problems .

and also i did my whole swap cheeper with off the shelf stuff over there over priced crap . i feed mine just fine with acdelco ep381 pump and stock 87-91 sender pump clips directly on and efi tank . its still going now and feeding my edelbrock pro-flo 4 with better results over the sniper .

good luck hope my info helps and my complaining dont bug you .