I feel many know this now, but maybe not. Years ago this was never a issue cause there were not all these environmental devices added to tanks. In modern cars you really shouldn't ever over fill your tank. Keep in mind every vehicle is different and so is every pump. The advice of always stopping at first click is kinda the all in safe place to stop and never have a issue. Now most Id say 2 clicks is fine but every click you go up you are increasing your risk. I am a very OCD type person, so when getting gas I like to always round up the amount it costs. So if pump clicked off at 41.18 I feel compelled to make it 41.25. I have done this for years and never had a issue yet.
While the issue is usually a messed up sensor etc with over filling there are other potential problems. My last truck was bought at three years of age. Upon purchase it had a full tank of gas. After about a week I needed to fill it up. As soon as it clicked off this splash of gas came flying out of the filler pipe. Thankfully I wasn't near it. So of course I thought it was a pump issue and that was that. Well the next fill up, at a different station it did same thing. I asked a local dealer, place purchased wasn't local, why this would be happening and was I doing something wrong. He replied with, " You just bought it correct? You need to bring back to that dealer and have them deal with it cause it was a safety issue". I contacted the dealer and explained the situation and they arranged for me to bring in. After looking it over they determined the previous owner apparently over filled tank often which led to build up and blockage in some of the venting. So basically what happened was as you filled tank air was getting trapped in there. When pump would stop the air trapped in tank would force the gas left in filler pipe out.
