This code says its for a large evap leak and before this id be at the gas station and about every gallon or so the pump would stop like the tanks full. So far ive changed the purge valve and caister vent valve. Ive also bought 3 different gas caps so any help at this point is much appreciated, also has a bit of a rough idle

 

Edit: Sorry. I missed that you replace the purge valve already. Your best option is to smoke the system and look for cracks. I've had to replace cracked pipes on my truck but on my suburban it was what I outlined below.

I spent hours trying to track this code down. I built a smoke canister to pump smoke into the evap system but never could find the leak. I then tested the evap canister purge valve and it was bad. The reason I couldn't find the leak is because I removed the hose from that valve to do the testing on the system!

On the 2005 suburban, remove the engine cover and it'll be right there in the front sticking straight up with a green cap, host and wires attached to it. You remove the hose/cap assembly from it along with the wire connector. Remove the bolt and pop it off the engine. You can then test it to see if it's functioning or not. If not, replace it. If it is, you'll need to smoke the system and look for leaks.

There are many youtube videos on how to do this if you want to see if done first.

 

Hi thanks for the advice anything at this point helps it driving me crazy. Yeah i guess smoke test needs to be the next on the list and how did you build your own machine? Ive seen some people say it could be the carbon filter canister, is there a way i can clean it just to see if thats the problem.

 

I bought an all metal paint can, drilled two holes in it then screwed a brass ****** nipple into one hole and sealed the nipple edges with silicone. The other hole I screwed an air compressor nipple into it and sealed it. I then attached clear tubing to the nipple and hooked it into the evap hose at the engine. The compressor nipple was then hooked to my air compressor. If you do a google search for Make Your Own Emission Control Leak Detector you'll see many variations on how to do it. If you don't have an air compressor, you can use an electric tire pump with tire valve in the can or you can use another nipple with hose and have a helper blow into hose while you look for smoke.

I can't remember what I used for the material to make the smoke. Maybe a piece of cotton or lantern wick soaked in mineral oil. Can't remember what I found that worked well.

I then set the compressor at a very low psi. Enough to get smoke coming out but not too much to where it would pop an evap line.

Next, I got under the car and looked for smoke coming from where it shouldn't. When I did this on my truck, I found it leaking around where the hose plugs in to the canister. The hoses were all cracked on the inside edge allowing air in.

 

to leak test a evap system for gm products...you need a scan tool to close the vent valve...its normally open. that is what vents the tank when you fill. modern evap testers have a flow meter that you monitor...if the flow meter drops after filling the system...you know the system is leak free...no need to chase smoke.

if you are still getting a slow fill...you have a blocked vent path. the tank must vent out a hose to the evap cannister...out the vent valve..out to a fresh air filter. a blockage in any of the mentioned parts will cause a slow fill. remove the hose from the tank at the cannister...blow thru it...back to the tank and then blow thru the cannister...there should be no restrictions.

I would have to check the build...if your system uses a fuel tank pressure sensor...it monitors purge by watching for a change in tank pressure when the purge valve is open.

 

Go remove the charcoal cannister, I bet it is leaking charcoal and your vent line is clogged. That is why the gas pump stops because the air coming from the tank as the fuel enters cannot escape. You'll have to replace the charcoal cannister, drop the tank, and blow the vent lines out with compressed air or simply replace them. I ended up adding a screen to my charcoal cannister so if it goes bad again it does not clog up the vent line and I won't have to drop the fuel tank again.