Quirky gas gauge

[blown motor]

When I turn the key on the gas needle goes up to 1/4 and then back to empty, up, back... the truck has not been moved so the gas is not sloshing in the tank. No matter how full the tank is the needle bounces around. What causes that? 79 Dodge truck.

[Bullitt-]

  A good guess would be something like Jaybee illustrates with these sending unit videos
https://forum.e-bodies.org/interior/6/inconsistent-gas-gauge-readings/26168/msg298605#msg298605

[blown motor]

Thanks @Bullitt- I hadn't seen that.

[Jay Bee]

Sorry Murray, I was planning on pointing you to that thread BUT thought you read ALL my posts (lol).