My truck is a 2003 silverado 3500 w/ duramax. I jumped into it to get to work, looked at the fuel gauge. Gauge registered no gas with the low fuel light on. I thought someone had siphoned my 50 gallons of diesel out. Limped to the gas station to pump in another $150. in fuel. Low and behold I pumped only 20 gallons in. Gas gauge defective. No problem, I'll just set the trip meter. I drove 361 miles and ran out of fuel. I usually get 550 miles. Thought, what crappy mpg I got! Again, I limped to the gas station and filled the front tank and continued to the back tank. To my suprise, the back tank was full. So, there must be a solenoid switch or valve that isn't working as well. Anyone have any idea's?