Question I have a 93 S10 Blazer with a 4.3L V6 gas engine. The engine turns over and has good spark but won't fire. I have fuel pressure at the bleed valve just prior to the air intake plenum when I turn on the key, but it quickly bleeds off and the in-tank electric pump doesn't restart until I turn off the key and turn it on again. I have replaced the fuel pump relay, no help. Too many electronic controls etc for me to understand. I hope you can help me with a troubleshooting tree process and/or a suggestion of the problem....Neal...
AnswerHi Neal,
When the key is turned to run, the fuel pump in the tank should run for two or three seconds, and then quit. if the ECM is recieving a crank signal, meaning the engine is rotating, it will keep the pump running.
There is another system that supplies power to the pump, and that is an oil pressure switch, that powers the fuel pump as long as there is at least 4PSI of oil pressure, so if the engine is running, one or the other system will send power to the fuel pump.
Sounds like your pump is operating fine, assuming it is puting out 14PSI at that test port.
What you may be missing is injector operation.
Check the fuses marked Inj.
If the fuses are good, you can check for voltage at the injectors. A "noid" light, available at parts houses will help. While cranking the engine, the noid light should blink, meaning there is voltage at the injectors, and there is pulsed ground from the ECM.
If you have voltage, but no pulses, you could have a bad crank sensor, ECM, or wire connection.
Van
