Under the hood is usually a green cap. I have see them down low near the frame too.
Follow the lines to and from it looking for obvious problems. Those lines should go back to the tank and charcoal canister. I have had people crack the canister's with rocks or ??? so I JB Weld (Plastic Weld) the cracks and good to go. A quick look may save the cost of a smoke machine or smoke test.
Exactly the situation in my case. 2005 grand cherokee 5.7. Evap code and eng light. My buddy smoke tested it at his shop and found the charcoal canister had cracks on it. Vee’d them out and jb welded. All good. Passed inspection. Would have never found it as it was cracked on top of canister. Saw smoke coming from wheelwell area and led us to that location to find it.
