New problem on my '98. Turn on the truck, have 1/2 a tank of gas, then suddenly it drops to zero and gas light comes on, sometimes it'll shoot back to correct 1/2 tank. Only does this when the truck is not moving, such as idling or waiting in traffic. Any ideas where to start?

 

Connector at the fuel pump module.

 

The sender is 20 ohms full to 220 ohms empty. So what you describe is a potential disconnect. the FPM connection has a locking tab, but still could be coming loose. Other option would be worn out contacts on the level arm.

 

Guys, that is some great info, give me a good place to start. I will check into it and I'll report back what I find.