Gas gauge 1/2 full

[truckin 79]

So my gas gauge reads 1/2 full and I am pretty sure it is full. I tested gauge with 9 volt battery and swings to full and empty when applied. I ohm tested and it read 90 ohms between top posts. I have 2 old gas gauges and they read about 45-50. I thought I would switch resistors and would fix problem but hit 1/2 tank again after swap. I can move needle to empty or full add power and still moves back to 1/2. What is my next move? Thanks

[truckin 79]

One more question are all turbo 400 kickdown gas pedal switches the same

[Palf70Step]

It probably is the sender unit in the tank. Drop the tank, and swap it out. Took me about an hour and half manhandling a full tank of gas on my 81.

[Pontiac1976]

might be sticking sender leaver, bad leaver slid connector, bent leaver, dented tank, or something wrong with gauge.

[Dead Parrot]

The gauge on my CUCV would only read about 1/3 full when the tank was 1/3 or more full. When the fuel was less then 1/3, it read the proper amount. Swapped the gauge with a different gauge and the replacement works fine. Read later that the problem was probably a bad resistor in the gauge(not sure if I read it here or over on Steel Soldiers). Haven't pursued the issue any further as the current gauge works(it is labeled unleaded instead of diesel) and there are other things higher on the to do list.

If you know those other gauges are good, might use three clip leads and substitute for the combo unit as a test.

[truckin 79]

Well I was under the truck changing the vacuum modulator since I also feel truck is not shifting at consistent rpm. Well I was able to trace tank sending wire and it looks like the metal tube that protects the wiring harness by the starter may have slipped down and exposed it to hot exhaust. I kind of looked wire(s) over and it did not look like any burnt/exposed wire but there probably is. The sending wire also had several spliced areas under the frame, not good. I still have to take out the old fuel tank selector switch since I am not running two tanks. So I will probably drop tank to run new rubber lines for a single tank and change out sending unit wire at the same time. Just more things added to the list. The good news is my new inner door panels arrived from USA1, so even if truck is rough on the outside. On the inside the truck will look close to brand new.

[Pontiac1976]

truckin 79

Well I was under the truck changing the vacuum modulator since I also feel truck is not shifting at consistent rpm. Well I was able to trace tank sending wire and it looks like the metal tube that protects the wiring harness by the starter may have slipped down and exposed it to hot exhaust. I kind of looked wire(s) over and it did not look like any burnt/exposed wire but there probably is. The sending wire also had several spliced areas under the frame, not good. I still have to take out the old fuel tank selector switch since I am not running two tanks. So I will probably drop tank to run new rubber lines for a single tank and change out sending unit wire at the same time. Just more things added to the list.

Wow sorry to hear the list got bigger. Oh if you got dual tanks make sure if it has any wiring off them making a full switch over( connection )
truckin 79

The good news is my new inner door panels arrived from USA1, so even if truck is rough on the outside. On the inside the truck will look close to brand new.

Well that should look nice, don't for get the pic when you finish it.

[Dead Parrot]

If that dual tank setup had the one wire solenoid valve, the switch changes which tank sender is read. Any chance it is set for the wrong side? Based on your many splices observation, I wouldn't trust the switch label. A PO might have tried to wire around a bad switch by swapping things under the truck.

[truckin 79]

Well like I mentioned I have some gas gauges. I have jumper wires from gauge and bolts sticking out back. When I hooked up gauges I get different readings from 3/4 to full on existing gauge. So I added another resistor to these bolts and now it reads past full. Would this work or is this just wishful thinking

[Pontiac1976]

Yes it can work if every thing in the wiring grounding set up is good. But you would best find out if the sending unit moving up to full the try your resistor then test at 1/2 then empty if does not read right try another resistor till you get them work together correctly.

[truckin 79]

Well interior doors look much better IMO. A nice mix of used and new parts. Some new weatherstrip and tinted windows as well. The gas gauge has not been tested on a trip yet, so don’t know if it works properly with extra resistor.

[Pontiac1976]

Looks pretty nice the inner door panel now.