Haven't been able to reliably put gas in my 2019 Ram 1500 for over a month. Had it at dealer about 3 weeks ago to have them diagnose and replace what I believed was a faulty filler neck since it was replaced once before by them under warranty for the exact same issue: gas handle clicks off immediately when fueling. After having it all day, they called and said they think it's the vapor canister and will have to order one. I reluctantly agreed to their diagnosis so I picked up the truck while they tracked down a new canister; good thing I didn't leave it with them! After a couple weeks of waiting, I went ahead and ordered a new fuel neck (revision "J") and a vapor canister (revision "D") from an online Mopar retailer
www.moparpartsgiant.com. Today I installed just the filler neck and viola! problem is fixed. Ram has had real problems for their 1st edition capless filler necks, hence revision *J*. If you have a 2019-21 Ram with capless filler neck and cannot put gas in the truck, put this in 1st as it's only about $50 for the part and replaceable fairly easily at home.
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