It starts half the time, and whenn it dosen't I just have hit the Gas Tank about 6 times with my hand.

Yes Sir, thank you for your time, a little about me , I retired, and I was a industrial mechanic before becoming a Electrician, anyway I have a 2003 Yukon 5.3 Vortec, still a Great Vehicle, 120k miles, always starts in less than a Crank, yesterday I went to the Post Office, and it didn’t start, after going in for 5 minutes, I checked the standard things, had a half a tank of gas, even though it was acting like it was out of gas, I hit the Fuel tank with my hand a half dozen times, and it started it ran without a miss all the way home, 5 miles, ever since then, it starts perfect sometimes, and sometimes it doesn’t start till I hit the Fuel tank with my hand a half dozen times. It’s a California Vehicle, if that makes a difference, Have you heard of this problem, and do you have an idea, of what the fix is ?

Thank you very much for your Time, [email protected]