Crank but no start-please help

[Tonyrodz]

Not yet. I ran the fuel pressure test and it was on the low side at 46psi. I took it to a small repair shop and they got 49psi on their pressure test. They said that is within range to start the truck so they don't think it's a fuel issue. They found that their was no spark at the coils. I replaced the plugs and wires less than 6 months ago but I've never replaced the coils. It's at the local Chevrolet dealer so they can diagnose what's wrong. Hopefully they will have something for me next week.

I doubt it's all, or even 1 coil. They all don't quit at once. If it was only 1 coil coil, you'd get a random misfire code for that cylinder--if it was cylinder 2 it'd be a P0302.
If it's no spark--I'm definitely no expert here--possibly could be a wiring issue. I can't wait to see what they find. Hopefully it won't be crazy expensive.

 

[Doubeleive]

running fine and dying under a load would point me to look for a poor ground, start wiggling wires and inspect all over, sometimes a wire harness rubs on something and wires get rubbed and break or are exposed and causes issues, sometimes a wire can break internally.

 

[Doubeleive]

for any one else you can always try to be preemptive and look under your hood and check all your wires and harness to be sure they are secured properly and not rubbing on anything over time wires droop, clips sometimes break and let the wires hang, engine movement pulls on them, always a good idea to take a close look at everything and adjust as needed

 

[Blackie]

running fine and dying under a load would point me to look for a poor ground

I did take off the grounds (except the one that's wedged between the engine and the firewall) as you suggested previously and cleaned the contact points good before reconnecting them and no luck. I believe it is a bad ground or wire that came loose but could not for the life of me find one!

 

[Doubeleive]

I did take off the grounds (except the one that's wedged between the engine and the firewall) as you suggested previously and cleaned the contact points good before reconnecting them and no luck. I believe it is a bad ground or wire that came loose but could not for the life of me find one!

the coil pack harness has it's own ground, so does the injector harness.

 

[lyncht1967]

If coils all arent delivering spark i would suspect a wiring fault in ignition coil circuit. most likely ground (g102 ground on side of engine is known for getting corroded and is the common ground point for all coils) or power but maybe reference low. all coils share a common wire for each of these three and an intermittent short in any one of them would take down all coils. Here is a good video showing this exact problem on a 2009 Sierra but GMT800s are the same configuration on coil wiring. You can skip to around 15 min mark for coil section. Shows how to test each wire.

 

[Blackie]

If coils all arent delivering spark i would suspect a wiring fault in ignition coil circuit. most likely ground (g102 ground on side of engine is known for getting corroded and is the common ground point for all coils) or power but maybe reference low. all coils share a common wire for each of these three and an intermittent short in any one of them would take down all coils. Here is a good video showing this exact problem on a 2009 Sierra but GMT800s are the same configuration on coil wiring. You can skip to around 15 min mark for coil section. Shows how to test each wire.

Thanks for the input lyncht1967. The truck is currently over at my local Chevrolet dealer. I talked to the service advisor yesterday. He said the truck is in the repair bay and the tech working on it is on vacation all next week! Luckily there's no rush on my end for me to get the truck back. He said with the bit of diagnostic tests the tech was able to do, he thinks the problem is in the passlock 2 system/module. At one point, I did get a code for the passlock system so it seems he is on the right track. Once I get more info and the truck fixed from the dealer I'll be sure to post what the problem was in the hopes it helps someone else in the future.

 

[Blackie]

So I finally got the truck back today. According to the dealer, it turned out the Passlock and the PCM modules failed and had to be replaced. So, $2,191.15 later my truck is running like a champ again!

Thanks to everyone who posted in efforts to help out.

 

[Tonyrodz]

So I finally got the truck back today. According to the dealer, it turned out the Passlock and the PCM modules failed and had to be replaced. So, $2,191.15 later my truck is running like a champ again!

Thanks to everyone who posted in efforts to help out.

Pretty expensive, but at least it got figured out. Strange, the pcm went bad on the pcm in my old 01 work van. It actually was the same condition--it would start fine all during the work week, but if it sat over the weekend it wouldn't start. Did your old pcm have corrosion on the wires? I never understood why GM would put the pcms under the hood instead of inside the vehicle.

 

[Blackie]

Pretty expensive, but at least it got figured out. Strange, the pcm went bad on the pcm in my old 01 work van. It actually was the same condition--it would start fine all during the work week, but if it sat over the weekend it wouldn't start. Did your old pcm have corrosion on the wires? I never understood why GM would put the pcms under the hood instead of inside the vehicle.

I didn't get to see the old one as they kept it for the core and I didn't think to look at it before I took it to the dealer for repairs.