Hi everyone. I've got a problem with a 1999 GMC jimmy/envoy. Its got 272k miles. So basically, I moved it into the garage one day and it fired right up and ran great, then the next day it wouldn't start at all. I checked the fuel pressure and it is at 65 psi when priming and sits at 60 psi. Remains above 55 psi for about 25 mins, but after 45 mins or so it drops to 10-15 psi before finally hitting zero. As soon as the pump primes though, it jumps right back to 65.

The problem now, however, stumps me. It will start right up the first time I try, but if I immediately shut it off and try to start it again, it will just keep turning over. After 15-20 seconds, it'll finally stumble to life, but will die if I touch the gas pedal for the first 15 seconds or so. Then its good again. It idles smooth. I don't smell any leaking gas. If I let it warm up after starting it, it will restart no problem every time! The fuel pump is relatively new (YES its acdelco lol) as is the fuel filter. No codes either. I replaced the coolant temperature sensor thinking that maybe it was telling the computer it was a different temp, as well as my scanner telling me that the engine goes into closed loop mode as early as 130 degrees. But it didn't help. Also the catalytic converter has rattled since i bought the truck 2 years ago and it recently stopped rattling.. Could a plugged converter cause my issues? Does anybody have any ideas about what it could be? Its driving me insane.

 

Anybody?

 

Could be fuel pump check valve. you should do the Max Pump pressure test at the outlet side of the fuel filter. Should be 70 to 100 PSI from the pump. Check that for leak down also. Could also be the fuel pressure regulator in the spider assembly but i would still check max pump pressure just to be sure pump is good.

 

Fuel pump tested good just now. I'm just curious now why it'll fire up no problems first thing in the morning (even with temps well below zero) but if I shut it off before it gets warm and immediately try to restart, it'll turn over for 15-20 seconds before catching! If it's warmed up completely, it'll restart quickly every time. It just seems temperature related to me. When it acts up and won't start for a while, the fuel pressure is still 64 when the pump is running.