Fuel Gauge Issues
 

All, I'm having some fuel gauge issues. Currently, I have a full tank of gas and the fuel gauge stays at 1/4 of a tank. I've done the following and it still isn't working.

1. Replaced sending unit
2. unplugged the wire from the sending unit and the fuel gauge went to full. Plugged it back in and it went back to 1/4.
3. Unplugged the sending unit wire at the fuse box and the fuel gauge went to full. Plugged it back in and it went back to 1/4.

What are my next steps to diagnosing this issue?

Re: Fuel Gauge Issues
 

Pull the door sill plate at the bottom of the drivers side door opening and check the wires to make sure they are OK. The Dome light wires run under there too, check them also.....

LockDoc

Re: Fuel Gauge Issues
 

Thanks for the tip. The wires look good to me. Any other advice?

Re: Fuel Gauge Issues
 

Read Tbone's thread....:)

http://67-72chevytrucks.com/vboard/s...d.php?t=640615

LockDoc

Re: Fuel Gauge Issues
 

How long did you replace the sending unit. The new ones are known to fail because of bad solder joints which will give you a bad reading. I posted a thread on a plastic float that is a great replacement.

Smitty

Re: Fuel Gauge Issues
 

Had the same issue...drove me crazy, try grounding the sending unit.

Re: Fuel Gauge Issues
 

I had the same problem with a aftermarket unit I found a NOS unit on ebay no more issues

Re: Fuel Gauge Issues
 

Just replaced it this weekend. My next step, after testing wires, is to pull the sending unit back out and test it.

Re: Fuel Gauge Issues
 

Check and make sure the harness is plugged all the way in on the instrument cluster, the circuit runs through there and I have seen issues with that connection with the water temp and fuel guage.

Re: Fuel Gauge Issues
 

Remove the old sending wire at tank and fuse block. Then Run a temp wire to re sending unit and fuse block marked fuel
Make sure to ground the sending unit.
This way you can eliminate it was a wire issue from tank to fuse block.
Keep us posted.

Re: Fuel Gauge Issues
 

Make sure there is nothing interfering with the movement of the float on the sending unit.

Re: Fuel Gauge Issues
 

Thanks for the tip. I'll give it a try next time I work on the truck and let you know. I live in one city and house the truck in another, so I only get to work on it once every few months.

Re: Fuel Gauge Issues
 

If you have not figured this out yet, remove the resistor from the back of the gauge and ohm it. It should be in the 85-88 ohm range across the poles.

If you get less than that, replace the resistor. I suspect you will only get around 22-25 ohms, if the resistor is bad.

This is one of the more typical reasons why a fuel gauge will only reach 1/4 full when the tank is actually full.

Typically a ground issue or lack of it will cause the gauge to peg past full (around 3 o-clock position).

Truck and Car shop in Orange CA, sells replacement resistors for factory gauges

Hope this helps,
Tom

Re: Fuel Gauge Issues
 

This is great info and I’ll for sure try it when I get a chance to work on my truck again. I’ll report back if this is the issue. Thanks!