I farm but I am not a mechanic. I have a 2004 Silverado 1500 for farm use. Recently could not start. Finally tried checking under vehicle to see if something was pulled loose in field. I pulled and reattached plug on Vapor EVAP Canister Purge Solenoid Valve. Stated up but would not restart after shut off. after a couple of times following that sequence again, I was able to get the truck out of the field and back to the barn. Then that stopped working to get it to start. After reading online that EVAP solenoid can get stuck and cause no-start. Then I tried the Vapor Canister Purge Valve Solenoid on top of the engine. It started right up but then the same. I have to remove the plug and reattach, then it starts. I ordered a new Vapor Canister Purge Valve Solenoid thinking that was the problem, but still won't start. When I finally get the right sequence of wiggling the plugs or spraying contact cleaner, it starts perfectly. But then no re-start until some other sequence works. Ideas?

 

Check for codes, even if the CEL isn’t on.

If the EVAP system is truly causing the no-start, it’s because it’s completely plugged up and as the fuel pump runs, it’s creating a vacuum on the tank that’s preventing adequate fuel flow through the pump.

In theory the gas cap should be venting in this situation, but it’s not unheard of for the valves in the cap to stick, or for the caps to also get plugged up. Being a farm truck, it wouldn’t surprise me if either or both were the case.

Remove the gas cap and see if it starts/runs OK more than once. If yes, you can delete the EVAP components but that will cause the CEL to stay on and eventually Pull a bunch of dirt/debris into the tank.

If you want the system working properly, the charcoal canister, vent valve and gas cap will need replaced. The purge valve might be OK but that can be checked after the other components are replaced.

 

Well with gas cap off it started right up. But then I turned it off and it would not restart. I checked wiring at both the purge valve solenoid ( no start) then at the canister at gas tank. It then started again, shut off and it started a second time, then third time no start. When it is running, there is no sign that it will stall. It runs good. Just once I turn it off, that's when it wont restart. And I have no way to read codes unless I want to take a chance and drive it about 4-5 miles to have it checked.

 

Then I’d suspect something other than the EVAP system causing the no start. It may still need attention, but the cap being off is for sure allowing it to vent properly.

When it doesn’t start, is it just continually cranking, or will it start and sputter/stall? If the latter, is the security (Passlock) indicator on the cluster illuminated?

Can you check fuel pressure? Given the fact that it starts/doesn’t start with key cycles, the fuel pump could be failing or there’s an intermittent wiring problem. If you can’t check pressure, see if it will fire with starter fluid (only use short bursts of fluid when cranking).

 

It just cranks when it wont start. When it starts, its like there is nothing wrong at all and runs great.
Good question about security indicator. I do see something like that illuminate and not sure if that is off when it does start. I have no gauge to check pressure, but after cranking, I can release pressure from the spot there above the engine ( sorry cant remember what that's called).
Also, I just borrowed a code reader from my neighbor. I've never used one before but 15 codes come up.
C0237
C0300
c0305
C0306
C0321
C0327
C0359
C0374
C0379
C0550
B0790
B2725
U1301
P0300
P1631

 

It just cranks when it wont start. When it starts, its like there is nothing wrong at all and runs great.
Good question about security indicator. I do see something like that illuminate and not sure if that is off when it does start. I have no gauge to check pressure, but after cranking, I can release pressure from the spot there above the engine ( sorry cant remember what that's called).
Also, I just borrowed a code reader from my neighbor. I've never used one before but 15 codes come up.
C0237
C0300
c0305
C0306
C0321
C0327
C0359
C0374
C0379
C0550
B0790
B2725
U1301
P0300
P1631

 

Gumby22 - You asked the right question. I had no idea what passlock was. I did the passlock reset and it started right up then restarted multiple times. The passlock light stays on now while the engine runs but does not flash like it was doing before reset.

Thank you so much!

 

You’re welcome - as soon as I saw the P1631, I suspected it was security related.

If the problem returns, try starting it with a spare key and see what happens. There’s not much inside the key heads to malfunction, but like any other part, they can wear out over time for a variety of reasons.