Fuel /Air problem

[remote]

1991 f250 7.3 today started running as if air was getting in system at first, engine rpms up and down while on road and surging while stopped or low speeds. Went to dinner and shut off motor. Truck was unusualy hard to crank( usually fires right up). Two hours later went to lowes shut truck off. truck didnt want to crank when i came out. Popped hood and bled scrader valve while turniong motor over. Finally cranked but not quickly. Went to parts store and bought fuel filter and replaced. Again bled schrader valve and eventually cranked even though i had primed new filter with fuel. After that the motor still acted as if air was entering system. Not all the time but ocasional surging while idling or running down road. Went 9 miles stopped and ate supper while leaving truck idling. Left diner and drove @ 5 miles to shop. Pulled truck into shop on concrete let idle . At first engine acted as if it was catching small amount of air. It leveled out and idled fine for about 20 minites. I checked under frame from diverter valve forward, and removed air filter to look at injecters and return lines. All were dry and found no sighs any where of leak for fuel to escape or air to enter system. Shut truck off for couple of minites. Cranked it again, it ran for about 15 seconds, died. Tried the usual that I had done, bleeding valve etc. but no effect. truck still has not given sighns of cranking. Either has never done anything for this truck but slow the turning over down. All Ideas are appreciated> thnaks remote

[cdnsarguy]

Did you switch tanks to one over 1/4 full....... could be broken off fuel pickup screen.

[remote]

Switched tanks, both full of fuel. Did that on way to shop where truck is now. Almost positive is not problem with tanks.

[cdnsarguy]

Try useing a direct fuel link to the lift pump from a fuel can..... Check the hose at the Lpump for a bad kink........ use a long enough pigtail when replacing that hose so no kinks can happen.