Fuel Sending Unit again

I was able to buy a used fuel pump (the whole thing). Unfortunately, they gave me a 98 pump instead of a 99. It looks exactly alike execpt that the float is on the other side compared to my original 99. But since it fits right, I used it and also check the contacts. I even tested the damn thing before I bolted the tank and it workED. After putting some gas into the tank, the damn gauge went up and started to blink again. CEL is off though. When I make a sharp turn, the gauge goes to level for a while and then goes to Full again.

What's wrong this time? I made sure that the contacts are ok.

Sounds like you have a bad sending unit.

Will the 98 vs. 99 pump have any effect on it or is it just the sending unit again?