CJ7Vortec

No I haven't watched the pressure it died. It normally dies driving around and I don't have the tester connected during that time. My scanner is just a basic reader and doesn't have a lot of options. I can start unplugging sensors and seeing if those make a difference but the O2 sensors are brand new AC Delco replacements. It's just a confusing thing. Talking with the PSI tech guy he said that it sounds like a pressure problem. The tester I was using I don't know if it's accurate or not. At Idle it's at 50 psi and the needle is bouncing rapidly. At WOT it shoots to 55 and bounces around rapidly. I can't see it being a fuel problem but the tech guy says it is. When it's cold it's adding more fuel and when it's hot it leans out per PCM specs. He's saying that when it's hot, it's not pushing as much pressure and that's the problem. However when the engine is hot it doesn't always cut out and die it's only intermittently. Sometimes it's perfectly fine and will act normal and other times it decides it wants to act up.

Could it be a fuel issue I guess, it just seems a bit weird for it to act the way that it is and the pump be the issue. Fine when cold and sometimes fine when it's hot. It is a new pump designed for this swap..but hey idk. lol it's just confusing and irritating. I'm at my whits end and I'm almost done with this swap and this problem is stopping me!

kingtal0n

iTrader: (1)

you need to put fuel pressure gauge on the car that you can read when the engine stumbles. That will point you either towards fuel system/wiring or sensor related, the most likely.

CJ7Vortec

FIXED!!

So I got another fuel pressure gauge and checked it, and kept it on the rail during the entire troubleshoot. Started it up, ran like a champ, got warm started to stumble. the pressure starting out according to the gauge was around 48psi. ( I think the gauge is off a bit) and when it started to stumble it went down to 26 psi and stayed there no matter what. After trying to find the cause i notice the pump doesnt prime when the key is turned to the ON position....I start checking wires and the spot where I had the computer and Pump tapped in for a constant 12v key ON and CRANKING source was only putting out 6v...I start probing around with my multimeter for a 12v source constant, tap into the new location, and what do you know, we're back up at what the gauge says 48 psi. No fluctuations, no stumble just raw power.

So I take it for a test drive and drive it like i stole it. Handled everything we threw at it and even had the 31's spinning.
Needless to say I believe I fixed the problem and it's running like a top.

I'd like to thank everyone that had input and helped in any way they could. And I'm sure you'll be hearing from me again once i start plumbing in the go fast parts. Thank you everyone!

G Atsma

Cool man! Gotta feel to have it fixed, AND know what caused it! Plus, your troubleshooting skills just went up a notch or two!