I'm trying to chase a fuel pressure problem. Sometimes when I turn the key forward, I get normal fuel pressure and the car seems to start up normally. Other times, the fuel pressure will just drop to 10-20psi and the car will not start. I noticed that when I hooked up a spark tester and cranked the car while at 10-20psi, there was no spark. Could this be an issue with the PCM or is it programmed to not spark below a certain fuel pressure?

 

The PCM has no direct way of actually measuring the fuel pressure. The only common problem that I see would affect both spark and fuel pressure would be the supplied voltage. When you only have 20psi at the rail with the key on, verify the fuel pump is getting battery voltage. I am assuming there are no fault codes? This is a intermittent problem? Any work recently done on the vehicle?

edit: on startup, the amount fuel (not to be confused with fuel pressure) is determined using predetermined values with the information supplied from the CTS, MAP, and MAF. I recommend first finding why there is a lack of fuel pressure.