All right, pardon the length of this post, but I want to include as many details as possible, because at this point, anything could be a clue, as I think you will see. TLDR at end of post.

The truck in question is a '98 GMC K1500, 5.7 Vortec V8, and an automatic transmission. The truck has a bit over 200k, but overall still in pretty fair shape. The last time the truck drove was July 2nd, I had driven it from home, a bit over 20 miles to the car wash (where I work), and while I was waiting to enter the automatic wash, is when the truck stalled. I had just put the truck in drive, getting ready to pull in, and it stalled out a few moments after going into gear, it was not immediate. I pushed it out of the way, and after it sat for a few minutes, I did what little diagnosis I could then and their, but had to have the truck towed home.
I had to fly out of town on the 4th, so I didn't actually start working on the truck until I got back, approximately 1 week ago. So far, I have cleaned the battery terminals well, and used a load tester to verify the battery was still good. After that, I checked for proper fuel pressure under the hood, on the line just before it enters the intake (central fuel injection on this motor, more on that later) the truck has 60 psi of fuel pressure. Next, I checked for spark with a inline spark tester. I do have spark. Initially, I thought the spark may have been a little weak, so I did take the cap off, and I didn't like the quality of the rotor inside, the metal tab on the inside was very flimsy, so I did change that out. I also used my ohm meter to check the coil and check for power and ground their. My memory is a bit bad, but I recall the Ignition Control Module being on the same bracket, right next to the coil, and I believe I checked it for power and ground too at the same time. The distributor is fairly new, just a couple years old, and with a few thousand miles on it by now. Everything else, including the plug wires seems to be in very good condition. What is weird, especially since it only happened once, is when I checked for spark on cyl #3, the truck somehow, fired up and did run for just a few seconds, it ran extremely poorly though, and would not idle. I assume it was misfiring badly. I next attempted to fire the truck up using starting fluid, to see if it was a fuel injection issue. However, I did not proceed with the test, as when we began cranking the truck, it backfired and shot fire out of the throttle body. I didn't feel like spraying starting fluid into a backfiring engine. I can't assume that that is great for the engine, and also not particularly safe. After seeing this backfire, I wanted to verify timing, to make sure that something like the timing chain hadn't slipped. So, I set the crank to TDC, cyl #1, and the rotor was in fact facing the #1 wire terminal exactly. So, after verifying mechanical timing was correct, that has lead me to believe that something electrically is not happening correctly and/or not at the right time. I have a Haynes repair manual, which specifies how to test the cam an crank position sensors. I have unplugged both sensors, one at a time, and have found they are getting power and ground. Their is a slight voltage drop, but not dramatic. I believe it was in the high 11 volt range, like 11.7v or 11.8v. The battery, even after a lot of cranking is still over 12v, its relatively new. The manual then specifies to back probe the signal wire for each sensor, and says i should see about 5v AC (I assume that is while cranking, but maybe it could be at idle, the book does not specify from my recollection). Initially, I saw something closer to 3v. I purchased a new cam, and crank sensor, and when I changed out the cam sensor, I saw no change. When I changed the crank sensor yesterday afternoon, it was reading somewhere between 3v-4v. Not sure if that is any significant improvement, so for now, the new crank sensor is installed in the truck, and the original cam sensor has been reinstalled. After this, I used a noid light kit I had purchased to check for injector pulse. I removed the rather large connector on top of the intake that powers the fuel injector spider/all 8 fuel injectors. I checked a few terminals, and did get a flash out of the bulb on each one I tested.
So, seeing that I have fuel pressure, injector pulse, and spark, I am running out of ideas as to why the truck does not run. I would like any thoughts or suggestions. I am assuming now that electrically, either the fuel, or the spark is not working correctly. Maybe something to do with the PCM? Any diagnostic tips for that would be much appreciated. Also, I think it would be a good idea to check for good ground for the engine and computer, so please share how I can do that.

Additional information/clues: The last work done to this truck was a fuel injector spider replacement. As soon as I started diagnosing it this month, I have been suspicious of that spider, but I am confused how the truck could stall out, because as far as I can remember, the only electrical component/part of that spider, is that their is a plastic body that all 8 injectors are housed in, and from what I know, and I could be wrong, but I believe that those injectors do plug directly into the wiring harness I removed, and checked with the noid lights. If I am wrong in any way in that assumption, I would like to know. Usually, in a situation like this, I look at what the last repair was to the vehicle when searching for a problem. The reason I replaced the spider this spring was actually to try and resolve a long crank issue the truck was having. The problem wasn't dramatic, but the truck would crank for 1-2 seconds before it would fire up, which is abnormal for this truck. It usually lights right up, immediately when cranking. After a lot of diagnosis, I was going into that repair because I figured it was the fuel pressure regulator that was causing my issue. the truck was loosing fuel pressure just sitting for a few minutes in the driveway, and I figured the long crank was a result of a bit a flooding. I did replace the whole spider though, not just the regulator. I did that because I know those spiders like to fail, and with this being a high milage truck, I figured it was time for the injectors to get changed out anyways. After that repair though, the 1-2 second crank remained! That was frustrating, because that was a hard repair to do. And, I will add, I do think that that regulator was in fact leaking. For those of you familiar with the central fuel injection on these trucks, you know that the regulator is inside the intake, and the intake is 2 pieces, an aluminum lower, and a plastic upper. Underneath the regulator, the aluminum of the manifold was bright and clean, where as the rest of the intake was black and dirty, as you may expect on a 200k+ motor. I did notice a increase in power after that repair though, so I do believe those old injectors where getting tired. The truck has been driving just like that since May.
And one final detail, that continues to confuse me. 2 times this summer, I have gone to crank the truck, and had no power in the cab whatsoever. The first time it happened was months ago, I went to fire up the truck, put the key in and turned it, and got nothing. No crank, no lights, no buzzer, nothing. I cycled the key two or three times in confusion, and then, all of the sudden, had power, and everything was completely fine, and the truck fired up and ran as normal. This was very unsettling as this is the truck I take into the woods, and need to fire up when I am 50+ miles from town. It has done that only one time since, and that has been while I have been diagnosing this crank-no start problem the past week, I have probably cycled that key dozens of times this past week. It was much the same this time too, I turned the key, got nothing. Before turning the key back off again though, I did verify one thing, not even the dome light, or the map lights in the cab worked. Completely dead. Furthering the weirdness though, when the truck died initially at the car wash, all the lights where on on the dash when I looked down at the gauges, so if it did loose power, it could have only been for a second or two, I wasn't watching the gauges, I was looking out the windshield when it stalled. And I tried cranking it multiple times to get it to start before having it towed that day.
Thank you for not only reading all of that, but for any advice!!! I hope I didn't leave any details out.
TLDR: Truck stalled while idling in gear, waiting to enter automatic car wash. Good fuel pressure, spark, good battery, and injector electrical pulse present. Most recent work done to truck has been fuel spider replacement in May, trying to eliminate long crank issue. Long crank issue not solved by spider replacement. Truck has also had no power in the cab 2 times this summer. Power has returned to cab after cycling key a few times on each of these two occasions.

 

I'd start wiggling wires. Corrosion somewhere.