Busted Gas Gage

[Stinky]

On my '86 720....the gas gage started not wanting to go under 3/4.  Then, every now and then it would bottom out, going below E.  But, when I got gas, everything was almost normal again.

 

I just finished putting a 4.10 R&P in it and it pulls much better now.  I pulled my trailer to the scrapyard and no slipping the clutch to start out....anyways, when I had it the stands, ass in duh air, the gage went to the bottom.  I've got gas since then and it hasnt come back up.

 

I assume that it is the float...correct?

 

Are the floats affected by the new gas?

 

I have an '83 King.Cab that I used to teacha guy that he should give people more space, before turning left in front of them.  Are the tanks and floats the same?

 

 

[datzenmike]

If TEMP gauge is not working say so. That's a different problem.

 

 

If reading 3/4 when there is definitely less gas then the float is stuck.

 

 

The sender is a variable resistance. The lower the resistance the more current flows the higher the gauge reads so...

 

0-10 ohms..................... FULL

24.5 ohms..................... 3/4

37 ohms........................ 1/2

56.5 ohms..................... 1/4

80 or more ohms........... EMPTY

 

No gauge reading is empty but could also be an open (break) anywhere in the circuit and no current can flow. This would include a bad gauge, broken wire, bad (loss of) ground. Here are some things to do to identify what's wrong first before tearing out the tank and sender to find out the gauge was bad or a broken wire all along.

 

Unplug the Yellow wire at the tank and ground the end. What should happen is the gauge should read FULL

1/ YES it reads FULL. This means that everything back to the gauge is working properly. Go to 3/

2/ NO still reading EMPTY. Something wrong back towards the gauge. Go to 4/

 

3/ Plug the Yellow wire back in and ground the Black wire to the tank sender. If it now reads FULL then the ground wire is bad. Check the black wire for a break if nothing found provide a good ground to the black wire. 

 

4/ Probably the gauge but under the right side (passenger) seat is a 10 pin connector that joins the cab and frame harness. Disconnect and ground the Yellow wire to the gauge. What should happen is the gauge should read FULL

YES gauge reads FULL now. The Yellow wire between the connector and the sender in the tank in the frame harness is broken or 10 pin connector under seat not making contact. The frame harness is exposed to the elements including road debris thrown by the tires. I had a 521 and had trouble with loss of tail lights and signals. A previous owner had spliced in a trailer towing plug and made a rotten mess of it.

NO change. The problem is between the passenger seat and the gauge... most likely the gauge. It'll have to come out, possibly the  10 pin connector beside the steering column that connects the cab and dash harness not making good contact. Sometimes just unplugging and plugging back in cleans it.