Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace) - Page 7 - Team Camaro Tech
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post #91 of 103 (permalink) Old Oct 28th, 14, 08:08 PM
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Tom Anderson
 
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

You know guys those are some really great helpful tip on the ways to go about fixing things
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post #92 of 103 (permalink) Old Feb 14th, 15, 08:05 AM
 
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Re: Gas Guage Failure. . .How to fix

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Originally Posted by 69-Pace View Post
Common issue with first gens. Easy troubleshooting to isolate if it is the gauge or the sender or the harness.

Unplug the sender lead in the trunk - in a 69 it is the brown single wire connection.
Turn key to on position.
Gauge should read past full.

Now ground the end of the harness leading back to the gauge - NOT THE LOOSE LEAD GOING UNDER THE FLOOR TO THE SENDER.
Turn key to on position.
Gauge should read past empty.

If it does both of these the gauge is in working condition and harness back to instrument panel is in working order. If not you can test the ohms being sent to the gauge as described below for the sender test, or have a buddy loan you his gauge for a second and plug theirs in and test as above.

If both gauges fail - and your description of your situation sounds as if the gauge is fine to me - the harness may have cracked or broken wire. You can also alligator clip the brown lead of the back of the gauge to a ground to do the above trunk testing to isolate wiring.

But if the gauge moves to past full then past empty with the trunk connector test, then problem is most likely the sender unit in the tank, or its ground.

The sender uses a ground fixed to the back passengers side tank strap and that is where I would start if you can get under the rear you should be able to visually inspect if the wire lead is corroded or loose. If it looks ok and is clean of corrosion it still may not be ok, and you can hook a test lead alligator clip to the connector at the tank strap and then the other end to a new clean ground you have made on the chassis and see if your gauge now reads correct with the key in the run position.

If you have a good ground at the tank or with your new temp ground, you reconnected the lead in the trunk and you still have a past full gauge reading, then maybe the sender unit itself has lost the will to live.

To test the sender you need to test the ohms (resistance) with a simple multimeter.
You measure across the loose lead in the trunk to the connector to the gauge. You
should read anything from 0 to 90 (empty to full). If you are getting something close to what you think is in the tank, the sender maybe ok. You can manually manipulate the float valve with a bamboo rod or wooden dowel through the filler neck. DO NOT USE A METAL ROD. Last thing you want to do is set your tank of gas and your ride, garage and house on fire with a spark. You can also affect change by removing or adding fuel to the tank as you check the ohms.

If you get a change in resistance the sender is most likely ok and the connector in the trunk may have been loose, or the float may have been stuck. if it is flaky better to replace then rebuild in my humble opinion. Dropping the tank is not an easy project without help or a lift and storing gas may not be easy where you live (condo owners take notice your neighbors may rat you out). And if you rebuild, how long would it last before it found its own groove again and left you high and dry.

Hope this helps you find your issue.
Brian
New member here. Great informative site by the way!

I too have the 3:00 fuel gauge thing going on and here's what I found so far:

At the fuel gauge, I have 12 volts on one side and meter shows 8 volts on the other side. I ground the 8 volt side and the gauge goes to empty. Unground and it goes back to 3:00.

In the trunk, at the sender connector, wire shows 8 volts, showing me the same as the back of the gauge so the sender wire is intact from the back to the gauge. If I ohm the sender wire to ground, it shows 44 ohms.

I ohm'ed the fuel tank to a body ground and it shows continuity. I can't get to the sender without dropping the tank, which at 44 ohms, is probably half full or better. I am stumped at this point, unless the sender itself has to have a separate ground. I don't see a grounding strap going to the tank.

Any ideas from you gurus?
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post #93 of 103 (permalink) Old Feb 14th, 15, 09:31 AM
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Al
 
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Re: Gas Guage Failure. . .How to fix

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Originally Posted by Svickers View Post
I am stumped at this point, unless the sender itself has to have a separate ground. I don't see a grounding strap going to the tank.
It does. A wire with a ring terminal end, bolts to the passenger side tank strap mount at the front


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post #94 of 103 (permalink) Old Feb 14th, 15, 09:54 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Well you have isolated the issue to the sender unit. If you are speaking about a 69 you can manipulate the sender with a wooden dowel through the filler neck. If 67 or 68 not an option. If you can change the sender arm position and the ohms change then the sender is working. Your reading at 44 is between half and 1/4 full. Zero is empty, 90 is full tank. If that sounds like your true reading of whats left in the tank you are in good shape so far.

So the issue is more then likely the ground lead which is not the easiest thing to get to but if you remove the rear pass wheel you can get to it. You can alligator a test lead to a known good ground location and if you get a reading on the gauge with power on, its the ground location. Then you need to just scuff and clean the area and re-tighten the screw with a star washer. That should give you a good ground IF the lead is in good shape from the sender cap.

If the lead is dead you have to repair or replace which will require the tank to be dropped. You can test the lead for continuity before the big drain.


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post #95 of 103 (permalink) Old Jun 1st, 15, 01:31 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Great info here.now I just have to go drive my car for a bit and use up some gas in case I need to drop the tank.

6 kids...= poor man...and I wouldn't have it any other way!

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post #96 of 103 (permalink) Old Dec 15th, 15, 09:40 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Brian,
quick question, after running thru all the processes you listed, is there a way to get to the inside of the gas tank via the trunk?
4 Screws hold the filler neck, by removing will I gain access?
I would like to use a broom handle & see if the float is stuck b4 removing tank & can't snake it around the bend of the neck from the outside.

Thanks,
Mike
'67 Camaro Convert. 327 4sp.
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post #97 of 103 (permalink) Old Dec 15th, 15, 11:50 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

I'm not sure in a 67 or 68 if you would have enough room to manipulate the float through the license plate opening once you remove the filler neck but if you can see the float from there you can move it.


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post #98 of 103 (permalink) Old Dec 15th, 15, 12:24 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

I seriously doubt you'd be able to get to it without dropping the tank.

I had to change my sending unit a couple years ago.

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post #99 of 103 (permalink) Old Dec 16th, 15, 09:23 AM
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Post Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Thanks Brian & George,
I'm getting ready to put her up for the winter so a tank drop wouldn't be that big of a deal. I hope.

Mike
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post #100 of 103 (permalink) Old Dec 16th, 15, 10:49 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Hey Mike don't jinx of Connecticut in California Winter by saying your putting her up for the winter. We can still ride until the first night they spray salt solution.


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post #101 of 103 (permalink) Old Dec 16th, 15, 12:39 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Got it!
Rhonda doesn't sleep until the 1st sand & salt!!!
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post #102 of 103 (permalink) Old Aug 21st, 16, 12:21 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Hi Guys

First post on this forum so i thought i'd make it a useful one. Hopefully it might save someone else some time.

I had been struggling to get my fuel gauge working in my 68 for a couple weeks now. Anyways here's the short version.

No matter how much fuel was in the tank it always read empty. Unplug the sender in the boot and the gauge pegs way over full to the 3 o'clock position. Tested the gauge and vehicle wiring with a decade box and that worked fine so Figured it must be the sender. Which is brand new by the way. Tested the sender at the plug in the boot and it reads around 0.5 Ohm. That would explain the gauge reading empty. Put about 20L fuel in the tank and resistance did not change.

OK tank back out and look at the sender again. With sender still in tank I used a stick to move the float manually. Had no effect on the resistance output of the sender. OK sender out and onto the bench. Tested on bench works fine hmm. Reinstall back in the tank and it's again 0.5 Ohm's regardless of float position. sender out again and eureka! spotted the culprit. The metal strap the joins the variable resistor to the wiring plug on the underside of the sender is missing some insulation and appears to be making contact with the tank. Give it a bend inwards to clear the edge of the hole where the sender goes into the tank and test. Sender now works as it should. Reinstall everything back in car and look at the fuel gauge now works.

Massive pain the the bum but got there eventually!
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post #103 of 103 (permalink) Old Aug 21st, 16, 08:00 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Good Catch Mat.


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