Evap Purge Valve

[BarryKH]

Does a failing Evap Purge Valve always throw a code. My 2013 Sierra sometimes cranks but won't start for a few seconds, DIC shows tighten fuel cap pretty often. I cleaned the fuel filler neck and installed a new cap, but still get the DIC message often. Sometimes if stopped for a minute or two at idle, it doesn't want to take gas and accelerate. Could the Purge Valve cause this without throwing an error code? No check engine light either.

[swathdiver]

4 hours ago, BarryKH said:

Does a failing Evap Purge Valve always throw a code. My 2013 Sierra sometimes cranks but won't start for a few seconds, DIC shows tighten fuel cap pretty often. I cleaned the fuel filler neck and installed a new cap, but still get the DIC message often. Sometimes if stopped for a minute or two at idle, it doesn't want to take gas and accelerate. Could the Purge Valve cause this without throwing an error code? No check engine light either.

No, it does not, it can throw them after time, once tests are complete.  I would be looking at fuel pressure for a no start and won't take gas.  

[richard wysong]

I agree , purge will not cause driveability problems

[richard wysong]

you may have to do a smoke test to cure the fuel cap message . any reason you think the purge valve is bad other than that?

[dna9656]

Maybe that canister near the purge valve is plugged up? I cleared mine out with a garden hose (water) and replaced the purge valve. My issue threw a code though I don't recall what the code was.

[tbarn]

Purge valve is nowhere the cannister.

[BarryKH]

On 1/2/2022 at 11:45 AM, richard wysong said:

you may have to do a smoke test to cure the fuel cap message . any reason you think the purge valve is bad other than that?

I kept having fuel cap problems on my cadillac and it turned out to be the purge valve. I replaced it and haven't had any problems since. I think the purge valve could be sticking a little sometimes making it seem like a vacuum leak. I don't know, it never fails to start, just sometimes you hit the starter and it will spin over for several seconds before it starts. I have even suspected the accelerator pedal module, I'm just trying to figure it out without spending a bundle on parts I don't need. Sometimes, after idling for a minute or two, and you start to take off, it stumbles, and will die if I keep trying to give it gas, but will start right back up and run fine. If it stumbles and I just ease back off the gas and give it a few seconds it picks up and goes. It has me puzzled. I am far from a master mechanic and depend on advice from folks like you for help when I'm in over my head. Many thanks.

[tbarn]

Easy enough to check a leaky purge valve. Remove the engine cover. Remove the air duct if required. Disconnect the electrical connector on the valve, idle the engine and remove the hose on the purge valve that goes back to the canister. If it is bad you will have vacuum at the port.

Edited January 5, 2022 by tbarn