I have a 97' with a 5.2L. I've been giving it some much needed TLC after some long trips and just not having the time and money to do some of the more in depth maintenance.

I did the TSB rerouting which fixed a small miss that's been eating at me for a while and then I started to check out the EVAP code I've had for a year or two.

The code is the purge solenoid. I replaced it and the code went away but the solenoid was clicking like crazy, I could hear it loud and clear in the cabin. After investigating I found that the canister was dumping crazy amounts of charcoal into the solenoid which seems to be the source of the clicking.

Now in my state I don't have to pass emissions because the truck is over 20 years old, so I pulled the canister, the vacuum line to the solenoid and the check valve that was coming off the solenoid, the line from the solenoid to the motor, and left the line from the tank to the canister hanging under the truck. I capped both vacuum ports on the solenoid but left it plugged in (still no code), and I capped the port on the motor.

The problem arises when I capped the line going from the tank to the canister. After doing this I didn't drive the truck I went in for the night and in the morning I started her up and everything seemed fine but I decided to pull off the gas cap and I heard a loud hissing, now I'm used to this when I fill up but this was much louder than before.

My worry is that since the canister is supposed to remove and recycle vapors from the tank will I end up creating too much pressure in the tank if I cap off the line from the tank to the canister? Also if I uncap it won't the gas just evaporate off over time and waste gas? I drove it to work with the line uncapped on a full tank of gas and it drove like it was brand spankin new, love it.

I have all the lines and such to reinstall the canister when I can pony up the cash for a new one but I'd like to just leave it off so I don't have to deal with the maintenance...

If I put the release valve that was connected to the canister on the end of that line will that stop it from building pressure and stop any gas from evaporating off?

 

The evap system is pretty reliable. Look how long the first one lasted. Chances are VERY good, that you fix this once, and you will never have to deal with it again. Eliminates a fair few issues associated with removing it.

 

Capping the line stops air from getting in or escaping from the tank! There is a vent(near the corner by the brake booster) that's where the air comes into the canister. At lease it was there for 96 and older a 97 may have changed. If you plan on getting rid of the system use that for a vent. If you look at your canister there should be a # on it and use it to search you may find it cheaper. If you are brave you can rebuild the canister but it's a pita.