Leak on the evap system wont stop it from starting, at least it didn't on my 05 Silverado. However, on the engine intake there's a plastic valve, that the plastic evap tubing attaches too, it could be stuck open, allowing too much air to enter the system. If you remove the plastic tube from the valve and plug it, just for testing, see if that may help the engine to start.

 

Thanks for the input. Are you referring to the evap vent solenoid tube connection under the truck that is mounted on the side of the fuel tank? Thanks

 

In addition I removed the intake air duct from the topside getting ready to do another smoke test to check under the truck for any leaks. I noticed someone had cut a hole in the plastic duct the size of a quarter dollar on the bottom, WHY? Thanks

 

There are two valves on the evap system , one near the tank and one on the engine. The 3/8ths plastic line that come from the tank, area, to the engine, connects to the valve at the engine

 

Going to search for the plastic valve at the engine attempting to trace line back to the engine. Is it on the same side as the fuel line and PCV line? An additional update I performed the smoke test and smoke was pouring out of the man made hole on the air intake at the bottom. Did not see any smoke coming out of any lines under the truck, however I used a man made smoke detector and not sure if I had enough pressure to travel the distance all the way to the evap vent solenoid attached to the back of the fuel tank. Used duct take to seal hole on the air intake at the bottom that is not suppose to be there. I removed the evap vent solenoid filter and removed all the crap in it, and reconnected it. I disconnected the battery and will re-connect in about a hour. I invoked a check engine light once I disconnected the evap vent solenoid. Oh what a day. Thanks for all the suggestions..

 

also changed purge valve on top of engine as well.

 

Well I have made an executive decision, calling it done as much as I hate to, unless there are any other recommendations. Given 3 mechanics and the stealership can't figure out this intermittent issue. I take pride in everything that I do and don't usually give up. My nature is to either figure it out or get it to someone that can fix it, so essentially, I don't feel to bad but I hate to give up on anything that I do. It just frustrates the heck out of me and I have spent way to much time and money on trying to figure out this non consistent problem. Every component has been replaced that would be the potential common causes of this issue. From crank, cam, throttle, air, injectors, coils, spark plugs, fuel pump, ETC, IAC, rebuilt PCM, PCV, and other components. No DTC codes to continue testing. I remember the stealership telling me it might be an internal engine problem. They suggested doing a smoke test, and a compression test which I declined. I performed the smoke test myself and I figured if it was a compression issue it would be somewhat repeatable and consistent, so I declined this service as well. The stearlership also told me it would be very difficult to even find a re-built motor. So I call it time of death 11:30 am Saturday morning. I will continue to drive it till it quits starting all together. 150k miles on a chevy silverado 2500hd. I hoped to get at least another 50k or 100k miles out of it, but it is what it is, we will see. Thank you all for following me on this journey and your valuable input|

 

Good Luck!