what year truck?

maybe a pinhole in the bottom of the tank?
carb wet at all? open holes in the firewall? rot holes in floor?
maybe running too rich with a bit of exhaust leak?

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot