Ok this is my grain truck but everything is basically the same. fuel system is simple. Tank to pump (mechanical) to carb. Truck runs great! Shut it off leave it for a couple hours and it has lost its prime for some reason. Dump some gas down the carb and it fires and as soon as the line has filled up again it idles itself. Shut it off and turn it back on and it fires right away. I thought it was my pump so i put a new one on, no difference. No sign of any leaks or drips anywhere. Im really stumped on this one. Any ideas?

 

What model, and or does it have any emission crap?

 

Its an 81, Ill have to check what size engine if that matters. No emissions stuff on it.

 

How old is the fuel pump? The diaphram in the pump holds fuel from it to the carb when off. Has it ever had any issue with just shutting off while running?

 

The fuel pump is only a couple months old, I changed it thinking that was the problem like you say but no difference. And no once you get that fuel to it it runs fine and idles fine not even a hickup.