Gas Delivery Problem

[Cris]

OEM:

I actually drilled a small hole in the cap to vent pressure.

The pick up on the in-cab tank is at the bottom, but then the hose goes up, exits the tank, then back down and heads to the engine and fuel pump. It almost seems an air pocket gets in there that the pump cannot overcome when the fuel level is low. The pump can't get the line "siphoning".

Crazy that I would be the only one with this issue. I must have something unique.

Tlhanks, Cris

[oem4me]

Originally Posted by Cris

OEM:

It almost seems an air pocket gets in there that the pump cannot overcome when the fuel level is low. The pump can't get the line "siphoning".

This makes perfect sense. Perhaps the pickup tube is compromised and draws air when the fuel drops below that level.

['63GENIII]

Hey Cris, might take a flashlight and see if you can see down to the bottom of the tank from the filler hole. Either that or pull the sending unit / pickup (when the tank is low). It should be silver and clean at the bottom.

Many times over the years these trucks are left with caps off or are left with a rag stuffed in them which lets rain water in. Water ends up rusting the tank. Rust plugs the brass sock on the end of the pickup. Worth a look. When I got mine, i could drive for miles on anything over a 1/2 tank. Any lower and there wasn't enough sloshing to keep the rust sediment off of the sock.

Also check the compression connection from the pickup line that's outside of the tank to the one that runs to the pump. You could be losing the prime there even if its not leaking fuel, the low tank level could siphon the fuel back into the tank from that point.

One last thing to check. IIRC, the sending unit is spot welded to the pickup at maybe 1/3 - 1/2 way up the tube. If one of those spot welds cracked, there may be a pinhole in the pickup. Like using a broken straw to drink a soda.

Good luck and let us know what you find.