Originally Posted by email@example.com
A friend has a 1997 Chevy pickup w/ fuel injected V6. Just had it rebuilt and has a problem. It won't start unless he drips some gas into the intake then it takes off and runs fine. I know nothing about FI systems but this sounds like a plugged start-up nozzle of some sort. Pump seems to work fine since it runs, just won't fire off initially?
These trucks use an oil pressure switch to power the electric fuel pump once the engine is running. Since the EFI needs fuel primed to start the engine, there is a second system that powers the pump for two seconds as soon as you turn the key to RUN. This is controlled by the computer and uses a relay to operate the pump. That relay is only used until the engine starts and the oil pressure switch closes. If the relay is bad, it will cause the symptoms you describe. An easy way to check is to turn the key to RUN (without starting) and listen for the pump. You may need to remove the gas cap and have someone listen at the filler neck while you do this. If you do not hear the pump, chances are the relay is bad. We know the pump is good, since the engine runs once you prime it.