Stalls when gas tank is half full.

[littlevx99]

I replaced my leaking gas tank with a used one and now my VX stalls when it reaches half full. It runs great until it gets around a half a tank of gas. I have no clue what could be causing this. Any help is appreciated.

[bartmanS4]

Did you use your original fuel pump and fuel gauge sender? How many miles are you getting from your half tank? I ask because I had a similar issue when I swapped to a new ECU until I swapped the fuel gauge sender from the same vehicle the ECU came from. The problem was the ECU was calibrated to the sending unit. It turned out the range of my gauge only went from full to half tank and it was actually empty just below half.
The other problem I've had is sediment from inside the tank being stirred up and clogging the fuel pump flow and the filter. This only occurred when below a 1/4 tank and if I shut off the ignition it would temporarily go away. I doubt this is your problem since you replaced your tank but who knows.

[tom4bren]

When mine did that it was the MAS. Easy to clean. Auto parts stores sell a special spray for it.

I don't know what the link was with the tank being half full but that's exactly what I was experiencing.

[Marlin]

Interesting, the LS1 powered buggy I wheeled with in Moab did some crazy stuff like that. The fuel suction line had come off inside the fuel cell. Being as our sending unit sits barely off the bottom of the tank, I would go with the gage error, or maybe even the sediment, but only if it starts after it stalls.
ANother thought, if the sending unit is going bad, it may not be enough suction head as the tank gets empty. A long shot, but if you put the old back in there...

[littlevx99]

I appreciate all of the advice. I put a used tank in so it could be the sediment issue. They broke a couple of screws when moving my fuel pump to the new (used) tank so I guess it could be the pressure thing too. The problem has gotten worse now. It only gets to about a quarter of a tank when it starts to stall. I can clean the MAS. You never know. I'll probablly call my mechanic again. Hopefully we can get it going. Thanks again.