I have a 98 GMC K1500 4x4 5.7 it will start then die after a second or so. My security light goes off the fuel pump will run , I replaced the fuel filter ,checked the relays in the fuse box and nothing changes. My oil pressure reaches about 40 or so before it dies at around a 1000 rpm I have not checked the mass air flow sensor and I did check the crankshaft position sensor, looked at and cleaned the dist cap and rotor. Any suggestions would be great . I have not checked the fuel pressure yet either. I looked at the mass air sensor , it looked fine and I also sprayed starting fluid into the air inlet after the air filter and tried starting the truck and it ran twice as long until it ran out of the fluid I am thinking my fuel pump is either weak or the filter in the tank is pluged . Still looking.