Losing fuel?

[DR-Rockso]

First post, but i have a hopefully easy to fix problem that i could use some help with.
1980-350-dual tank.
when i fill up the truck says full. after i shut it off and it sits for a little bit, i lose roughly 20-30% of fuel in that tank. i dont see any leaks, ive replaced the pump as well. my gauges are digital and it shows % not gallons. just not sure where the fuel could be going. anyone have a lead? thanks in advance.

 

[fast 99]

20-30% would be around 5 gallons. If there isn't a fuel trail or puddle something else is wrong. Not familiar with digital dash conversions. Someone will be along on that.

 

[75gmck25]

I had a mechanical fuel pump that sprung a leak and was squirting gas directly toward the passenger side exhaust manifold. Everything immediately evaporated, so there were no puddles of fuel, but it was easy to see and smell when the engine was running.

 

[Rickf]

Any fuel getting into the oil pan? If not I would question the accuracy of the fuel gauge.

 

[DR-Rockso]

Any fuel getting into the oil pan? If not I would question the accuracy of the fuel gauge.

Not that I can tell. I'll be replacing the Trans seal this weekend and I'll check

 

[DR-Rockso]

I had a mechanical fuel pump that sprung a leak and was squirting gas directly toward the passenger side exhaust manifold. Everything immediately evaporated, so there were no puddles of fuel, but it was easy to see and smell when the engine was running.

So I did replace the fuel pump not too long ago. I guess I should check that as well. Like I said it doesn't go down while I drive, just went it's sitting.

 

[Ricko1966]

Any fuel getting into the oil pan? If not I would question the accuracy of the fuel gauge.

So I did replace the fuel pump not too long ago. I guess I should check that as well. Like I said it doesn't go down while I drive, just went it's sitting.

If you had 5 gallons of fuel in your oil you'd absolutely know it. If you are in doubt pull the dipstick is it way over full? Somethings up with your gauge or sender