I was having problems with my '90 silverado recently where it would crank and start up just fine, but then die shortly thereafter. Subsequent attempts to start it would end with the same results. At some point, it would continue running.
It looked like there was fuel squirting into the TBI, but it appeared to slow down and stop as the engine died. So I wasn't ready to rule out fuel or ignition system problems yet, but figured I'd check the fuel pressure to ensure is was in the 9-12 psi range spec'd for these engines.
I installed a tee at the throttle body (see the fitting that come with
this fuel pressure gauge) to measure the fuel pressure. While I was installing the adapter, I noticed a broken plastic vacuum tube that goes from the EGR vacuum solenoid to the front of the throttle body. So I repaired the vacuum tube.
When I turned the ignition key forward, I heard the fuel pump run, and fuel pressure looked good, but the engine was still somewhat warm. I let it sit overnight, expecting to see the problem the next morning when I first tried to start it. The next morning, with fuel gauge attached, I started the engine...and it kept running! So at this point, I THINK the broken vacuum tube may have been the problem. Tomorrow morning, I may try disconnecting it and starting the engine to verify the symptoms return to ensure it's not a red herring. If it is indeed the root cause, it's a $0.39 fix (short length of vacuum hose to splice the plastic vacuum tube back together) to a very annoying issue.