So I just pick up a 95 gmt-400 k2500. When I started looking at it, it wasn't starting did some digging and change fuel filter and drain the tank of old gas. Fought around priming the damn thing for a bit. Got it running. Ran it around the area for a bit and let sit for a few week. Yesterday I started it idle fine, walked away about min or so dead. Turn it over again. She fired up after a few cranks and ran for about half a min died. Prime the fuel filter cranks it for a bit start runs for 10-25sec dies. Did that a few times till the battery's got low. Is this airlock or something else.