2008 fuel gauge always full
I've done some searching on here and I seem to have the opposite problem from most people on here. The gauge in my truck (2008 F-250, 6.4, base model) doesn't move off of full. It started a couple of weeks ago when I was showing a half a tank and then as I was driving I started watching it move back towards full. I let it get to full and then I stopped and opened up the fuel cap. It was hissing like I was taking a radiator cap off. I put it back on and started the truck up, now I was showing the half a tank agian. It worked properly on and off for for a week or two and now it doesn't move at all. Yesteraday I filled up, drove over 400 miles, and the gauge never moved. When I stopped to fill up agian I took the fuel cap off and it started hissing like it has been, but this time I heard something else coming from under the truck. I can't say for sure what it was, but it sounded to me like the tank contracting. I assume the tank isn't venting properly, but before I dive into this has anyone every expierence anything like this?