navyguy79

Hello all, I have a 99 Tahoe 4x4 5.7L. Five weeks ago I went home to Indiana on leave (military), first time the truck had seen severe cold weather. It started having trouble starting when engine was cold (open loop). I could cycle the key a few times allowing the fuel pump to cycle then get it started. I just chalked this up to cold weather and went about my business. I went out to my brother’s house which is open field in the country and the temperature dropped to 8 degrees without wind-chill. Truck would not start at all. Spent the night there and was supposed to drive back that day. I called my other brother who lives in Indianapolis and had him bring down parts that all have sensitivity to humidity and cold weather. We changed out the coil and ignition module before checking for spark, I know I know, but had clean strong blue spark. We shoveled the driveway and got it pushed into the barn. I checked the fuel pressure and it was around 60psi ruling out the fuel pump. I thought maybe the diaphragm in the fuel pressure regulator was going out, cold weather making it worse. I put a hair dryer on the intake above the regulator for a few minutes and it started right up. I loaded up and drove 13 hours home only shutting it off for gas. Once I got it home it was back to the same thing, no start, cycle the key a few times and it would fire up and start rough then smooth out. I thought I’d change the fuel pressure regulator when I could get some time. I did some travel overseas for a few weeks and it did the same thing for a few days, until it finally died for good. Now it won’t start at all, smells flooded after cranking and I get a P1351 code (ignition control circuit high voltage). After printing out the schematic and tracing things through four pages it looks like the ignition signal routes from the VCM to the EGR, crank position sensor, ignition module, coil, and looks like the pulse for the injectors. So what I thought was a fuel problem not seems to be electronic so I guess I’ll start pulling sensors and doing the good old Ohm check looking for a sensor that was going out and is now officially dead, check connections, double check my grounds, then hooking up jumper wires looking for the bad section of wiring. Does all of this sound like I’m on the right track? Anybody seen this before? Common problems I should be aware of? I need to go back out and make sure I still have spark before jumping all over this but I bet $100 I still have pretty blue spark. Thanks for any and all replies.

therewolf

Grounding. If it's old, just replace the negative cable. Also the engine -to-ground strap. Many years ago I had an epiphany; Bad grounds and bad cables are the "great imitator" in older vehicles-much the same as Syphilis is in humans. Level the playing field, get your grounds
right.

I've had car radios and other systems start acting up, just to see it straighten out when I changed the negative cable.

in2pro

I don't know that it is your problem but rivereye is right about checking grounds, loose grounds really can cause problems and ohm out the ground cable they can corrode inside the jacketing and look perfectly fine from the outside.
I would revisit the hair dryer to the intake, if that really did help and is repeatable then you may need to look at the fuel metering body...