98 C/K 1500 won't start

It might be a good idea to put a fuel pressure gauge on the fuel line at the engine and check for fuel pressure. It could be as simple as a clogged fuel filter .If the vehicle sits for awhile, fuel stabilizer and starting it weekly is a must, to prevent no starts.You can also prime the fuel pump, turn off key and press in schrader valve on fuel pressure line to help bleed the line and see if fuel is reaching the engine.This will cause gas to get on top of the engine so use caution.You might wanna Check your return and vapor and pressure lines also.If any one of these has rusted it could prevent fuel flow from the tank.I would also check all electrical connections at the injectors.

Thanks for the replies. I'll check the schrader valve later today. But if it's fuel causing the problem, shouldn't it fire when I use starter fluid directly into the throttle body? (I do open the throttle when I spray it) I tried starting it this morning and it fired a couple times right off the bat but it didn't start. I'm charging the battery as we speak.

Also, it's "dieseling" every after every time I turn it over.

Also, when I'm cranking it, every 5 seconds or so it stops and goes "thud" and then continues cranking.

I just checked the schrader valve. Fuel shot out of it.