Fuel Gauge Issue

Fuel Gauge Issue
A

Al Lindner

Jeeper
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Location
Richmond VA
Vehicle(s)
1980 CJ 7 258 CID T176
2004 F-150
I think I read EVERYTHING over the last two days on here about gauges but I didnt see this. I dropped and drained the tank, inspected the sender and float tripple checked all my connections as well as grounds. When I hooked every thing up and turned the ignition the gas gauge goes right to full, the only problem is the tank is empty! I havent put any gass in it yet as I dont want to have to drain it IF I have to drop the damn tank again. I'm HOPING i just have a wire crossed some where.
If anyone has a suggestion Im more than open to listen Im SO close to getting the "Quick " project on the road (year and a half and cuonting)
THANKS GUYS
 
Your gauge is reading full when tank is empty, probably because the sending unit has gone to ground. Either because the sending unit itself is bad, or because you have the wire going to direct ground someplace in the circuit. Of course, this is assuming that it's all wired and connected properly, which you said you have done and checked.....good luck!
 
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In just a few easy steps we can determine if you have a gauge problem, a wiring problem or a sender problem... You will need a cheap meter - they can be purchase at most auto parts stores, hardware stores, electronic stores or even discount stores.

With the tank empty.
1) Remove the sender wire from the fuel gauge. If it reads full (with the key on) the gauge is faulty. If it goes to empty the gauge is most likely not a problem.
2) Using your meter, check continuity to ground. Since the gauge shows full it will probably show a direct short to ground. Verify this.
3) Drop the tank.
4) Re-verify the sending wire at the gauge to ground with the meter. If it show open, then the tank assembly is shorting to ground (the sending unit stud may be rubbing the body). If it shows a short to ground then there may be a sender problem.
5) Disconnect the sending wire at the sending unit.
6) Re-verify the sending wire at the gauge to ground with the meter. If it shows open now then the tank assembly is shorting to ground. If it shows a short to ground then the sending wire is shorting to ground. You will need to trace the wire to find the short..
7) Using your meter, check continuity of the sending unit to the tank. The sender should show shorted to ground. The sender is stuck in the full position or the sender is faulty.
8) Remove the sender.
9) Using the meter, check continuity of the sending wire stud to the sender mounting flange at the floats lowest level an it's highest level. If the ohms change (from a low continuity to a full short) the sender is working as it should.

To verify correct operation. Connect the sender wire to the gauge and the sender. Ground the sender flange. Move the float and observe the gauge (with the key on). What happens?
 
Here you go! I’d look for a short or a bad sending unit but the wire between the fuel and temp gages can be troublesome too.
 
Another question I have Mechanical gauges (oil, temp, and Volt meter) installed so do I need to hook the electrical gauge up in order to make the gas gauge work?
 
Not sure how you have a mechanical volt meter as it relies on electricity to function. :eek:

So, Jeep did not use mechanical gauges from the factory. Can you post pics of your aftermarket mechanical gauges?

Thanks, :chug:
 
CJ said:
Not sure how you have a mechanical volt meter as it relies on electricity to function. :eek:

So, Jeep did not use mechanical gauges from the factory. Can you post pics of your aftermarket mechanical gauges?

Thanks, :chug:
Click to expand...


I could be way off here but I think he means his guages have a needle and that they are not digital
 
JSW - probably correct - just hoping to see some pics so we can help! :chug:
 
CJ, the volt meter is electrical. It is a sunpro not my favorite but inexpensive. The Oil pressure and thermometer are also sunpro, part of a kit. They do not require an electrical signal. I prefer Mechanical to electrical so I swapped them. I hope that clears things up. The reason I asked is I dont have the temp sender installed in the new block, I have a wet bulb in the water jacket with a cappillary tube to the sunpro gauge. The old OEM gauge is still in the speedo tied to the fuel gauge but the other terminal on the temp gauge is essentially OPEN
JS Watson, You are way off, but I appriciate the reply
 
I hope I didnt come off like an A$$h01e, JSW and CJ. I like the mechanical stuff better cause I dont have to trouble shoot electrical stuff, but I went and bought a multimeter and dug thru my tool box for a 12v tester I guess I'm going to learn to LOVE electrical trouble shooting
Thanks guys
 
CJ said:
Your good...

Let us know how the continuity tests work out! :)
Click to expand...
The "PINK" sender wire reads ground when its not hooked up to the gauge? If I have the hot "RED" hooked up to the "I" terminal,the gauge goes right to full. Also following one of the tutorials I should be able read resistance between the terninals and ground
Now I know this is going to sound dumb, but but do I need everything hooked up and key on in order to measure the resistance between the terminals?
Thanks
 
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