Please help!! 98 Silverado 1500 4.3 Vortek, We have spark & fuel. new cap & rotor, new fuel pump. The only time it starts and runs is if we pour fuel down the throttle body. Once it burns that it dies out. New cap rotor and fuel pump did not do a thing to get it running. I want to check the injector pulse, voltage, and ground. I have a multi meter but cannot find a pin layout for either the plug at the manifold or PCM. Can anyone direct me to finding a pin layout and required pulse voltage. I inspected the wire harness because it is getting cold here and though mice may have chewed something. The fact that it runs when we dump gas down rules out spark, and we have plenty of fuel pressure (at least 60psi). The only thing I can think of is the injectors aren't firing. Not even a fart from this thing.

 

Welcome to the forum. The fuel injectors are supplied the ignition voltage (battery voltage with key in RUN or START) on the PNK wires from the 20A ECM-1 fuse in the underhood fuse block. The VCM then grounds the other side to trigger the fuel. The VCM determines the injector timings from the CMP sensor input.

 

you may also have a bad fuel pressure regulator. this comes into play under the upper plenum, so you will still see fuel pressure up to the motor, but if the regulator is dead, then you won't actually get fuel thru the injectors. it's really a simple job, couple hours work and you're done. the regulator is under the upper intake plenum, mounted directly to the center injection unit, also called the spider.