94 7.3 fuel draining back?

[littlejoe]

That's what it acts like if it sits a while.

Seems like there ought to be a check valve in fuel supply side someplace.

????? tia lj

 

[Macrobb]

Yeah, that's typical. Check for leaks from filter head, through lift pump and back to FSV.
May also replace the lift pump if it's old - they have check valves in them, but over time they function worse and worse.

You can also add a new check valve to the inlet side of the filter head if you want.

 

[littlejoe]

Thank you much! Truck has been kept inside, 100k miles original. but age stuff. valve on filter sounds simplest. parts store item? thanks again~!

 

[franklin2]

There is no check in the fuel return line, and that is where the fuel goes back to the tank if you get a leak. I have been waiting for someone to try a 12v solenoid valve in that line hooked to the ignition key-on, but haven't seen anyone do it yet.

 

[Thewespaul]

The stock mechanical fuel pump on the block has a diaphragm that is supposed to act as a check valve. It almost never works. I put a regular check valve inline the soft hose between the frame and pump to solve this, but it sounds like you have a leak.

 

[icanfixall]

True it sounds like the mechanical lift pump is faulty and.. you probably have a leak at the top of the filter head at the fuel heater area.If the top of the filter head is slightly wet I bet thats the problem.