68 fuel gauge behavior - Team Camaro Tech
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post #1 of 12 (permalink) Old Oct 25th, 09, 04:26 PM Thread Starter
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68 fuel gauge behavior

When i got my 68 i was told the "fuel guage doesnt work" and was given a brand new sending unit with the car. I have not installed this yet.

When i pulled apart my dash and was checking wiring i found that the pink wire to the gauge assy was cut and had a pigtail spliced to it. I was told this was the fuel guage and i assume someone had a aftermarket gauge installed at one time. So I fixed this wire with the hopes that maybe this is the reason the previous owner thought he needed a new sender.

My tank is empty now. When i turn the key to the on position the gauge reads well beyond F all the way clockwise but slowly starts to move up counterclockwise.. I didnt leave it on long enough to see where it was going to stop.

So my questions are:
Would the needle ever go over there in normal operation??
When the car is off does the needle stay where it last read or does it park itself to one end or something??

What would be a easy test of the sender at the tank wiring without dropping the tank and pulling the sender out?
thanks
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post #2 of 12 (permalink) Old Oct 25th, 09, 05:03 PM
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Re: 68 fuel gauge behavior

There is a sticky on troubleshooting the fuel guage.

https://www.camaros.net/forums/showthread.php?t=73968

If you have a bad ground or open ground then the needle will go past the full mark. You can check the sending wire in the trunk area with DMV meter and at empty will be 0 ohm and when full it will be 90 ohm.

You can also do a search and there is alot of info on this site about fuel guages.

Mike
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post #3 of 12 (permalink) Old Oct 25th, 09, 05:07 PM
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Re: 68 fuel gauge behavior

The needle might go the normal positon. But every Camaro I've had, the needle would register the level its at, no overshoot, and needle is pretty damped, meaning rapid movement of the car/sending unit does not yeild the same results - slow action.

Needle generally stays in the last known position, but if off center, gravity may prevail and the needle drop to the side, not always.

The tan wire of the body harness goes to the sending unit. Testing this wire to ground would indicate the resistance of the s/unit. Sometimes the ground wire from the s/unit, the black one, going to the pass side strap needs a little cleaning to make a good connection.

Getting a 50 ohm (approx 1/2 tank) & 100 ohm (full tank, may read pass F) resistor, or a 0-500, 0-100 ohm potientmeter, and tie one lead to ground, the other to the tan wire of the disconnected harness to the gauge would help to see if gauge is working. It will never read exact, just an indication of level in tank.

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post #4 of 12 (permalink) Old Oct 25th, 09, 06:19 PM Thread Starter
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Re: 68 fuel gauge behavior

sounds good. Thanks guys. I will let you know what i find.
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post #5 of 12 (permalink) Old Oct 28th, 09, 06:46 PM Thread Starter
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Re: 68 fuel gauge behavior

reporting back.. So i had fixed the wire behind the dash but still had the fuel gage pinned beyond full. I started by testing the ground. I cut the original ground off and ran a new wire to a known good ground, still nothing changed. So i dropped the tank. Found the wire had been spliced on top of the tank in the same fashion as all the other wires in the entire car.. That is strip about an inch of each wire, lay them next to each other and then wrap them with tape about 5-6 times... It fell apart as soon as i touched it.. So i fixed that connection, and now the gage moved to about 1/2 full. Problem is the tank was empty... I then hooked up the new sender outside of the tank with temp wires. tested the gage in various positions and all looked well. Left the gage reading E and hooked the wires back to the original sender. Again it went to 1/2 full. So i swapped the new sender into the tank. Should be all set now... Only worry is if the new gasket at the top of the tank leaks.. I have had that happen in the past, smallest bit of rust or grit can screw up the seal and there seems to be no way to know till you go fill it... ughh.. here is hoping.
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post #6 of 12 (permalink) Old Oct 29th, 09, 03:39 AM
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Re: 68 fuel gauge behavior

Was OE sending unit stuck at half tank or wiper arm broke at half tank?
Reads like you have conquered the challenge.

Good luck on the leak check; the first hard braking situation will tell.

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post #7 of 12 (permalink) Old Oct 29th, 09, 05:04 AM Thread Starter
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Re: 68 fuel gauge behavior

It looked fine once i took it out. I didnt test it out of the tank. Hopefully there isnt something in the tank that was hanging it up. Cause the new one could end up stuck as well.. Will know soon enough once i get gas in it and start using it. wont be till spring though.
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post #8 of 12 (permalink) Old Oct 29th, 09, 09:06 AM
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Re: 68 fuel gauge behavior

Cool,,, glad you found the problem.

If you have a ohm meter you can check the sending unit with it out of the tank.

Mike
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post #9 of 12 (permalink) Old Oct 29th, 09, 11:01 AM Thread Starter
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Re: 68 fuel gauge behavior

Im going to get the tank back in the car and move on to the next issue.. dash lights flicker/on/off (mostly off) as you wiggle the headlight knob... hopefully just a bad connection? Maybe a bad switch/dimmer...
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post #10 of 12 (permalink) Old Oct 29th, 09, 05:11 PM
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Re: 68 fuel gauge behavior

You might grab the knob and twist the bejesus out of it. The rheostat usually gets a burn spot in the wiper and coil of wire it rubs against.

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post #11 of 12 (permalink) Old Oct 29th, 09, 08:35 PM
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Re: 68 fuel gauge behavior

An old electronic technicians trick for scratchy potentiometers might work to "twist the bejesus out of it". Grab about a 24" piece of string. Wrap it wround the potentiometer shaft and see-saw it back and forth. You might even blast a little electronic control cleaner in there, but I'd avoid the lubricated kind since the light dimmer gets pretty hot inside.

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post #12 of 12 (permalink) Old Oct 30th, 09, 02:54 AM
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Re: 68 fuel gauge behavior

I've been busted!........LOL

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