I have noticed off and on for a couple months that when I let my truck sit over night of for a couple hours that when I turn the key to start it, it has a pop or crack sound from the back of the truck. Its not from the exhaust. If I start it once it will pop or crack and if I turn it off and try it again, it wont do it. It sounds like its coming from someplace high like above the gas tank or the canister area. Was wondering if anyone else has had this happen? The little researching I did, it sounds like a valve on the tank or canister.
Thanks for any help.