84' K10 Fuel Gauge Issue

[HeciDeci]

Hello All,

I'm having an issue with my fuel gauge only being 50% accurate, the truck has a new 20 gallon tank, new sending unit, verified the tank ground, and the truck has about 10 gallons in it. The fuel gauge only shows a 1/4 tank, it should show 1/2. If I ground the sensing wire, the gauge goes to empty, as it should. If I disconnect the sensing wire, to my knowledge, the gauge should peg way past full. However, it only goes to full and stops. Checking resistance at the sending unit peg, to ground, I have 61 ohms, so the sending unit is working correctly. However, checking the sensing wire to ground at the bulkhead connector, I only show 25 ohms. If disconnect the sensing wire, and check it to ground, I get 45 ohms on the sensing wire. It should be an open circuit, correct? What is the deal with this thing? I'm at a loss with it. Any help is appreciated.

Thanks,
Tom.

 

[123jerryeric]

I am having a similar issues my self. I posted a thread also trying to figure it out! I read 65 ohm at new fuel sending unit (about 3/4 tank) but behind guage I'll only ready about 7 ohm (1/4 tank) with key off. And my sending wire seems to be fine (no shorts or pinches) and about everything else checks out too

 

[Jgonick]

Check for loose nuts on gauge terminals?

 

[Turbo4whl]

Check for loose nuts on gauge terminals?

Also, that resistor bolted on the back of the gauge can go bad. That is why it is replaceable. Different resistors for medium duty trucks with deeper tanks. Color coded line, (GM parts) for different value.

Poor ground on the gauge panel to body ground can be another issue.