When the rear tank is selected, engine starts and runs fine. When front tank is selected, it starts very hard, and just sputters. So when i start the truck with the rear tank, I can switch over to front tank, and it runs fine. Its only starting with the front tank that causes problems. Any ideas? Sending unit?

 

It would help to know the model year of your truck, but I see from your other post it's a '96. Each tank has it's own high pressure fuel pump. I suspect the front pump is bad in your case. A test with a fuel pressure gauge will confirm or debunk my suspicions.

 

My 96 F350 w/460, dual tanks did the same thing. Ended up with new pumps for both tanks. They are expensive, but I could afford it at the time and glad I did it. BTW, you should be getting some codes.

 

As a matter of fact, I am getting a code: p0174 "System Adaptive Fuel Too Lean Bank 2". One of the ten possible cause that it lists is that "The fuel system may not be supplying enough fuel (e.g. The fuel pump may not be supplying enough fuel)." It also suggest checking for multiple air leaks, MAF sensor, etc. Since I know there is an issue with the front tank fuel pump, and that's one of the possible causes, maybe I'll start there. Oh, and that tank has a very small leak, so maybe I change out the entire tank while I'm at it.