Yet another 2002 ZR2 Died while driving
 

Hey Y'all I joined the forum in hopes of a knowledgeable Blazer Pro could help. I have a 2002 ZR2, I had a few things happen in the last few months that I believe are related. On two separate occasions, when I get in to start the vehicle, it would crank, but would not start. I always wait for the fuel pump to prime before I start any vehicle. I tried twice more, same, crank no start. So i waited for a few mins, tried again, Voila! Started, and life was good. Earlier this week I was driving on the freeway going 65, I gave a little bit more gas to get up to speed limit of 70 and it jerked, like it was gonna downshift but couldn't. I found that odd because I was not going up hill, and did not give enough gas to warrant a downshift. My first thought was low tranny fluid. I stopped at autozone, I checked the level, it was on the upper end of the dipstick. Now yesterday, I left for work, I got 3 miles down the road, it hesitated again, but this time it died. I coasted to a stop, I gave it some time and tried to start. Crank no start. So I called my buddy, he towed it back to my house. First thing we checked was spark, which we had, we then took the distributor cap off, points were a little glazed. Took the rotor off, we seen on the bottom of the rotor was a little melted plastic. It looked like the spark, instead of firing at the point, fired through the rotor and went down the Dist. Drive Shaft to ground. Simple, we thought we had it. Also the battery never died, I was able to test crank over 10 times, it was a strong crank, wasn't weak. There were no codes either. When we got it back to the house i put it on the charger. So, I got a new ACDelco rotor and cap, installed it, same crank no start. So, I kept the battery on the charger all night. I went this morning to buy a fuel pressure gauge to check fuel rail pressure, and starter fluid. The previous owner upgraded to MPFI. I hooked the gauge up to the fuel rail and when the pump is priming I had 60 psi, after it primed, pressure showed 45. So I figured I would try to start it while the fuel is still priming, It started and ran just fine. (Rules out timing) After letting it run, I turned it off, and just to test out my theory I figured I would attempt start after the fuel pump primed and pressure is at 45. It starts, so now I cant replicate the problem. Im worried that the problem is still there, and it will wait to shut down again in the middle of the night, while im an hour away from home in a thunderstorm. Anybody have any ideas???? When i bought it last Nov the guy gave me a list of things he had done recently.

Fuel pressure is to low, needs a minimum of 52 psi to open injectors.may be pump may be spider under plenum. Also these trucks do not have points

Mine jerked randomly while driving before the fuel pump died. Your fuel pressure is too low after priming, read the sticky at the top of this forum. The next time its dead and you verify spark, move on to things not related to spark like fuel pressure. Let us know what you find.

George

Forgive my ignorance, but after the MPFI upgrade are there still mechanical poppets that require 50 psi to open? Also, when the engine is running, I have 50 psi and when I tap on the gas it goes to 60. What numbers should I be seeing? I've searched the forums, was on till 1am, I found so many different numbers. I thought the MPFI did away with the poppets.

Sorry, I meant the posts that the rotor fires to, don't know what that's called.

It did. Most upgrade MPFI pressure regulators control fuel pressure to 58 psi during the 2 second pulse after the key is first turned on. After the priming pulse is over, the pressure drops a few psi to maybe 52 or so. It should hold there for a fair amount of time and not drop right away. If not, then pressure is leaking past check valve back into fuel pump, or past fuel pressure regulator, or through injection nozzles, or leaking from the spider externally into the intake plenum.

Note that a dead-ended fuel pump puts out much more than 60 psi so don't block the exit from the fuel pressure regulator as a test.