Bad Gas Guage? - Team Camaro Tech
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post #1 of 13 (permalink) Old Sep 4th, 14, 08:08 AM Thread Starter
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Scott
 
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Bad Gas Guage?

1st off I read the sticky. I have a 69 with 2 gas gauges. The dash one is not wired. Looks like I inherited a console set of gauges and a new harness already installed. The gauge is wired in the console. It stays at 1/4 at all times and never moves. I tested the wire in the trunk and have no power there n I also tested it (brown wire) at the plug under the dash with no power there either. Was told there in a new sender and new tank. I checked and cleaned the sender ground to bare metal. Any ideas?

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post #2 of 13 (permalink) Old Sep 4th, 14, 08:33 AM
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Re: Bad Gas Guage?

Probably going to have to open up the console if the temp gauge works given the symptoms. Check the pink wire that supplies power to all the gauges. Power on the brown wire actually comes from there after running through the gauge circuitry. Should most likely be a jumper from the temp gauge to the to the fuel gauge (if fuel is installed in the front of the pod like original). Also check that the ground jumper is installed between the metal carrier/pod from the rear gauges to the front gauges.

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post #3 of 13 (permalink) Old Sep 4th, 14, 08:42 AM
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Re: Bad Gas Guage?

You need three things for the fuel gauge to work (as well as the gauge itself). You need ignition 12 volts, a ground, and a variable resistance from the sender.

Testing at the trunk does reveal things but not always so what a person needs to do is verify they have an ignition 12 volts and ground at the gauge. If you have those two things, disconnect the sending unit wire in the trunk and then back at the gauge turn the ignition on and see if the gauges needle is at full or above. You then need to do a second test to verify the gauge works and to do this you then short the sending unit stud on the back of the gauge to ground. The needle should then swing to empty or below (and you have to have the ignition switch to the run position). Now disconnect this wire from the gauges sending unit stud and the needle should then swing to the full or above mark.
If you get the needle to move to full and above and then to empty and below, then the problem is from the sending unit stud back to and through the sending unit in the gas tank and then to the point the sender is grounded.
If the gauge does not respond, one problem is the gauge is not working and you may still have other issues once the gauge is replaced and retested.

Jim

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post #4 of 13 (permalink) Old Sep 4th, 14, 09:02 AM Thread Starter
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Re: Bad Gas Guage?

I have no power to the pink wires or the brown wire at the gauge. I tried a ground jumper from front gauges to the back with no results.
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post #5 of 13 (permalink) Old Sep 4th, 14, 09:16 AM Thread Starter
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Re: Bad Gas Guage?

There are 2 pink wires coming out of the harness at the plug. looks like one goes to the neutral safety and has keyed power. The other has no power keyed or otherwise. Also the needle is missing from the ammeter and the temp gauge is also inop. The lights in the console a gauges work.

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post #6 of 13 (permalink) Old Sep 4th, 14, 09:32 AM
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Re: Bad Gas Guage?

There's the most likely culprit. See if they by chance left the old gas gauge plug hanging or if they left the dummy lights in underneath the dash gauges. Either one of those should have a 20 AWG pink wire with key-on power that you can use to power the gauges. If not there are spade connectors on the fuse panel labeled BATT, RUN, and ACC. You can slip a female spade/wire on the RUN or ACC spade and use it to power them.

I'm thinking the other pink may be for the reverse lights.

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post #7 of 13 (permalink) Old Sep 4th, 14, 10:29 AM Thread Starter
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Re: Bad Gas Guage?

I'm making progress. I ran the jumper wire to the pink wire. Powered up the gauges. Ammeter works!!. Temp gauge came alive. Gas gauge now moves. With unplugged trunk connector the gauge went past full. With the wire grounded in the trunk it went to empty. With everything hooked up it went to just under 1/2. Is that right??? Who knows...I thought there was more gas in there than that but maybe it gets worse mileage than I thought...Once I get the brakes figured out I'll go put some gas in n see if it moves.

Also any idea why the pink wire has no power naturally?

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post #8 of 13 (permalink) Old Sep 4th, 14, 01:49 PM
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Re: Bad Gas Guage?

If the sender line from the trunk is connected running the troubleshooter sticky will confirm if it is connected tot he gauge and the Ohm's reading will confirm if the sender is working.

Post what Ohm's you get from the sender in the trunk testing and that will tell you how much fuel it thinks is in the trunk.


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post #9 of 13 (permalink) Old Sep 4th, 14, 02:45 PM Thread Starter
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Re: Bad Gas Guage?

Quote:
Originally Posted by 69-Pace View Post
If the sender line from the trunk is connected running the troubleshooter sticky will confirm if it is connected tot he gauge and the Ohm's reading will confirm if the sender is working.

Post what Ohm's you get from the sender in the trunk testing and that will tell you how much fuel it thinks is in the trunk.

33.8 ohms. Sound right? Gauge reads 7/16 of a tank. That is measuring with the battery unhooked measuring the sender lead with the red lead and grounding the black lead. Looks like you say to measure between the sender lead a the wire going to the guage but I don't get a reading on my multimeter that way.

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post #10 of 13 (permalink) Old Sep 4th, 14, 03:27 PM
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Re: Bad Gas Guage?

Since the fuel gauge system uses a 0-90 ohm sender with 0 ohms to read empty and 90 ohms to read full, you can do the math to figure out what would be needed to get the gauge to read 1/2 full which would be 45 ohms. To get it to read 1/4 tank this would require 22.5 ohms and 3/4 full, 67.5 ohms. This would be if everything was highly calibrated but these systems are not.

33.8 ohms would relate to having the gas gauge read right about between 1/4 full and half full.

22.5 ohms for 1/4 tank plus 11.25 ohms for 1/8 tank would equal 33.75 ohms. You are pretty close to that number.

Jim

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post #11 of 13 (permalink) Old Sep 4th, 14, 04:29 PM
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Re: Bad Gas Guage?

Okay Scott. Since you have a 69 you can see and manipulate the sender float with a wooden dowel or bamboo plant stake if the Ohms increase as you lift the float to 90 or more then the sender would be okay.

If you have continuity up the lead to the back of the console gauge, you are set there too.

If you have power on the pink lead and ground on the grey you should be able to move the gauge if the trunk lead is disconnected at the trunk and then grounded as per the trouble shooter in the sticky it should peg. If it doesn't the gauge is dead. If there is no power on the pink, jump some to it from the cigarette lighter. If the gauge works then you need to find where the other end is disconnected.

I can see the resistor is in place but make sure the wire is not broken in the winds.

Brian


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post #12 of 13 (permalink) Old Sep 4th, 14, 05:23 PM
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Re: Bad Gas Guage?

Looks like I stumbled onto the right thread at the right time. I was concerned if my gauges were working correctly as well. My fuel gauge never goes past 1/4 full, but goes down as I use fuel. Further to that my ammeter gauge is always in the negative and if I turn the lights on the needle moves towards zero, but not quite. Water temp never goes above 1/4 either. Not sure if this is the same issue, but would love to know how to fix my problem as well. So far this is the closest I have come to reading a thread that sounds like a similar problem to mine.

Also regarding 12 volts constant, I just ran a wire from my fuse box to my coil as I am running a Pertronix Ignitor II as I was having ignition problems. Not sure if this problem is connected or not.

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post #13 of 13 (permalink) Old Sep 4th, 14, 05:44 PM
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Re: Bad Gas Guage?

Quote:
Originally Posted by 69z28freak View Post
My fuel gauge never goes past 1/4 full, but goes down as I use fuel.

Further to that my ammeter gauge is always in the negative and if I turn the lights on the needle moves towards zero, but not quite.

Water temp never goes above 1/4 either. Not sure if this is the same issue, but would love to know how to fix my problem as well.
Mike - First run the fuel gauge troubleshooter outlined in this sticky. Run all the steps then report the findings.
https://www.camaros.net/forums/showthread.php?t=195833

Some of the other gauge issues smell like a grounding issue for the gauge pack to the console mount and or your Voltage Regulator may be responsible for less than a full charge. The temp sender may also be failing to make a good ground on the block.

There should be a pair of grounding wires on each step of the gauge pack that tie to body ground. I would start there and then bench test each gauge if that doesn't square you away.


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