Pontiac Repair: 1999 Pontiac Montana, crankshaft rotation, pontiac montana

Question
The gas gauge has been reading full 90% of the time, and will fluctuate 10% of the time. I replaced a fuel tank pressure upon the advice of a ASE mechanic friend, but no luck. Wondered if this problem is common on Pontiac Montana's. I also replaced a crankshaft rotation sensor successfully to correct an intermittant tachometer reading issue.

Answer
Its a pretty safe bet that the sensor in the tank is bad, however there is always the chance that the guage or the wiring up to it has a problem.

But if what you said means you already changed the sensor, then you have a faulty gauge or one of the wires is shorting against a live wire.