I have a 1995 GMC Jimmy 4.3 L 4 wheel drive with CMFI injection. Most of the time, the engine runs perfectly smooth. Periodically the tacometer/RPM's will fluctuate. This possibly has something to do with temperature causing it. Recently it stalled and wouldn't start again. Starting fluid was introduced into the intake and it tried to run on the starting fluid. It was clear that there was no fuel to the engine. A fuel pressure check was done and the fuel pressure was holding steady around 55 as it should. During the fuel pressure check, with the gauge attached, the vehicle stalled. The pressure remained constant through the episode. This leads me to believe for some reason, the CMFI injector failed to deliver fuel. What would be the cause for the injector to intermittently cut out? The vehicle doesn't send out a trouble code. Are there any components that control the injector that do not send out a trouble code? Possible crank shaft sensor?? Any suggestions. Thank you so much.