Can someone shed some light/point me in the right direction. During a 5 hour drive yesterday my fuel gauge was bouncing up and down about 1/8 to 1/4 tank on straight level ground. The tank was full 38 gallon and did it all the way to 1/2 tank and stopped. Then continued around 1/4 tank. I jerked the wheel a little thinking float on sending unit and I could not make it flux. There was no common time/speed/incline/or decline that made sense. Any thoughts would be appreciated. Thanks

 

Did you fill the tank with the ignition turned ON?

 

No. Ignition off. I love to drive and have gone back and forth to Alaska 4 times. The truck is pretty consistent as far as fuel mileage. These fluctuations are abrubt not gradual

 

I always fill my truck up while running...is there something I should be aware of by doing this? My gauge has acted weird once after filling...the needle stayed close to "E" and the miles to empty went to zero and stayed there for a few miles. Once I got going and pulled up to the next light, the gauge read full and the miles to emply read 400.