Rusty fuel tank? Or sending unit?

[Warren96]

My 6.5 is getting air in the fiter making it stall. Since the sides of the tank are damp with fuel, i decided to take it down and have a look. I figured the supply line must be leaking since that is the only place air can enter the engine fuel filter . Since i had already replaced the line from the suction side of the pump to the tank, I expected to see the top of the tank soaked with fuel due to the steel nipples rusting. To my surprise the supply line isnt wet,just a little dark, and the outside of the tank was so wet i had to wipe it off to pull it down. It had over a half tank of fuel before i took it down, wouldnt you expect to see a lot more fuel around the supply line due to splashing? It isnt always under suction. So-o-o this long winded story brings me to my question ... Who else has had this problem and what did you do?

[Mark Rinker]

Just replaced the pickup unit on my '94 K3500. Same issue. The shop found an aftermarket unit for $200, GM wanted nearly double for theirs.

No apparent leak anywhere, just air getting into the system, causing rough running and eventually stalling. You could always find the air at the filter, that was the clue.

[Warren96]

Was the outside of the tank wet with fuel? Or just air in the filter?

[Mark Rinker]

Everything appeared dry, but very the lines and pickup fitting were very rusty. The theory is the air leak was outside the tank, somewhere on the rusted fitting where it wouldn't leak - at least visibly.

[Warren96]

Well, I poured a couple of gallons of fuel back into the tank and laid it on its side of the tank that appears wet, and sure enough,the part of the tank where the anti-squeek insulator is on the back of the tank is leaking also. With sales tax the tank and sending unit UNINSTALED at the dealer is over $900 bucks!