loss of prime

[nape]

I have an 86 army one ton, 6.2. It cranks fine but goes dead soon after and is hard to get primed back. Any ideas? Also how can I turn the fuel up?

[n0n0_1963]

Check the lift pump, mine was giving me some trouble, start perfect when cold but hard when hot, until one day nothin, I suggest also to go with a new fuel I think this one was giving me an air leak. Put a vacuum gauge to the inlet of the pump, use a long cheap hose from HD, and crank it, you'll see where you are.