Hi, So I've been having this issue with my truck for about 4-5 months now and have had no luck, I've gotten advice from multiple people and sources 2 of the people being mechanics. The issue started one day I went to the station and got some gas hopped back in started the truck, I sat there for a few minutes when all of the sudden the truck just shut off, I am not exaggerating when I say it shut off as quickly as turning a light switch off, no sputter no rough idle no check engine lights or codes just off. when I tried to restart it everything seemed normal but it didn't fire, so I stopped and thought for a bit (probably about 10 minutes) didn't know why it would just shut off like that but figured what the heck it's been sitting for a minute I'll try to start it again and boom success lol, started right up as if there was no issue let it idle for a couple minutes then drove home it ran great zero issues. Once I was home and had time to think while driving I felt this could be a bigger issue than just a random fluke so instead of turning the truck off I decided to let it idle and see if it would shut off again, so as I'm just sitting there 30 minutes goes by and nothing just idling perfect, 45 minutes nothing then about the hour mark like a light switch, silence, it just shut off again. I wait and try to crank it again after about 10 minutes and nothing, that was close to 5 months ago and many attempts to troubleshoot with no success, I've replaced the crank position sensor w/ a GM genuine sensor, didn't fix it. I seen where it could be an open ground on the ignition harness so I did my best to check those kind of hard to do lol and I seen that you could add ground to the ignition harness to possible bypass the open ground but no success, I even seen where some people were having an issue with 12v+ for the crank position sensor for the ECM and could pin the C1 harness #2 wire adding a 12v constant to it causing the crank position sensor to have no choice but to read, but no success. I've got one mechanic telling me that it could be the Ignition switch, and another is telling me to replace the cam position sensor. Much like many of us I don't have money to just throw at diagnosis and parts, and it is my primary vehicle I've been using the wife's car but that leaves her without a car and I really just need to get this issue sorted out. Any advice would be so greatly appreciated. Thank you

 

Sorry to hear about your troubles. It sure does sound like an electrical issue of some sort to me, to just cut out like that.

On the ignition switch I would look at the wiring diagram for your truck over at charm.li that you can figure out a bypass for that, and jumper things with a wire to bypass the switch being in the on position.

 

I appreciate it. that's what I've been hoping to find was a temporary bypass, you said to pull up the wiring diagram at "charm.li"? Just wanting to be sure I'm reading that correctly.

 

Yes. All of the 1999 manuals are available here:

https://charm.li/Chevrolet/1999/

I don't really know which module you have (C/K or 1500/2500/3500), or engine. But if you choose yours, the entire manual is there, and that includes wiring diagrams.

 

The truck falls under a c1500 2wd with a 5.3, even after finding the harness diagram I honestly don't know which wires should be jumped to bypass the switch. Any advice on that would greatly appreciated. Thank you

 

Soubnds like something gets hot and fails - like a coil or ICM

 

Before we dig into the wiring diagram, let me clarify something. You say you try to crank it now, and "nothing". Does it try to turn over at all, and not start? I.e. is the starter engaging, or is it just dead and no power to anything when the key is turned? Is anything powering up with the key in the run position?

 

Is that a common issue with the ICM?

 

So the truck does everything but fire and run. It cranks fine from what I can tell the starter sounds good and it sounds like it is cranking at a decent speed, all of the instrument cluster seems to be working as it should aside from the Tach, the information center clears off like normal it isn't saying security or anything. I have a check engine like but its been on for probably a couple years and has never affected the truck. I did try starting it with some starter fluid and it at times I felt like it sounded as if it had fired but couldn't be certain. I haven't put a fuel pressure gauge to it yet, but if I have someone else crank it and I press the Schrader valve in on the fuel rail it shoots fuel about 8ft across the drive way so I've kind of chocked that up as okay fuel pressure, but that doesn't tell me if the injectors are firing. But the long and short, it'll crank all day if you needed it to.

 

Ok, forget the ignition switch. If it’s turning the starter then the key/switch isn’t the issue at all. If there is fuel, but no ignition even with starter fluid, my next step would be to check for spark at the spark plugs. Look at the manual, and diagnose it. I would get a cheap ODB2 reader too if there are any codes set.