Hello I have a GMC topkick with a mui 3116. The truck stalled out one day on the highway when I drove over some rough pavement. I believe it lost prime and I could not get it to restart and had it towed to a mechanic. When the mechanic went out to check it out the next day it Started up. arrggg. Anyway I noticed it had pressure in the fuel tank( not a lot ). Is pressure in tank normal? I also didn't see a fuel hand primer!? Any thoughts on this truck, mechanics fixed a loose wire on the oil low side but could not confirm the truck is fixed. New fuel filters and such were replaced. I pick the truck up soon and its a 2 hour ride home. Any info could really help as I'm nervous about driving it.
The tank should have a vent tube and attached hose. It's probably plugged with dirt. As for the primer, mine don't have ones either. I added them, per Cat update, as prefilling the 2 micron fuel filter can, and does, damage the injectors prematurely. #5 in the image broke on both of mine, but it can be left out, leaving the pump horizontal instead of leaning upward. Just pay attention to the inner spring and poppet orientation.
topkicks are terrible to prime. Without a priming pump, you need a tube to the vent on the tank, and a wrench to loosen the fuel supply line up top and front by the governor/ fuel gear pump, I assume it's a gear pump, because it will NOT suck any air at all. Apply pressure to the tank, loosen steel line until fuel flows, tighten line and attempt to start. I agree, that vent is probably plugged and the tank couldn't vent. Possible you have other fuel line cracks too, they're getting old. I think I had a few issues, and cut the end off, warmed the plastic tube and stuck it over the fitting again. You should be fine with a full tank and a clear vent hose. Wouldn't hurt to have a length of hose to pressurize the tank and a wrench to vent the air when priming.