Fuel Guage

[gandalf]

I sense a problem in the making. Over the weekend I took the truck to Home Depot for some plywood. Much to my amazement I saw the fuel gauge pegged over full. I knew this couldn't be true since I haven't won Lotto. I tried switching tanks, and the rear read as I expected it to. Once the truck was warmed up the gauge read over full when moving, and dropped to half a tank at idle (right where I expected it to be). But as soon as I would start moving again it would jump to over full.

I ran the truck briefly yesterday and the gauge seemed to be working.

What sort of problem am I looking at here? Is the sender going south? Do I have an intermittent open line? Whats happening?

 

[fellro86]

The senders are well known for failure on these trucks.

 

[Agnem]

You didn't say which truck. On the 86', the IVR could be the issue. All your gauges would be reading high if that were the case.

 

[acousticrawk]

whats an IRV?

 

[Agnem]

The IVR is the Instrument Voltage Regulator. All the gauges in the 80-86 trucks are 6 volt, so the IVR (which is mechanical) cycles the 12 volts on and off with about a 50% duty cycle. If it sticks, it will put 12 volts to all the gauges, and they don't like that very much. The temp gauge is the most sensitive one I have found. And, prior to the internet I replaced my thermostat 3 times before finding out my truck wasn't overheating at all and it was just that dam IVR that was stuck.

 

[gandalf]

You didn't say which truck. On the 86', the IVR could be the issue. All your gauges would be reading high if that were the case.

Oppps. Sorry. I'm talking about the '92, the truck here in Cali. The '86 is in Maine, still waiting for an engine. Thats pretty low on the priority list.

 

[towcat]

check the ohm readings on the sender. chances are the one that is not working has had its plating eaten up the the fuel. If both quit at the same time, the FSV would be suspect but if one is working and the other is not, the sender is suspect.