My gas guage reads beyond full. I have visually checked the ground wires. It went bad while driving and I think I have about 1/4 or less gas. What should I check and what is the fix? I am thinking of dropping the tank and checking the sending unit. I would'nt think the wiring would just go bad while driving!
The Camaro Guy
Re: Gas Guage Failure. . .How to fix
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
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
Re: Gas Guage Failure. . .How to fix
Very detailed and appreciated diagnosis. I will be following your instruction this week end. The good news, I live in the country on an acre so no problems. . .I have all my Camaro parts along side the shop in the back!
Very detailed and appreciated diagnosis. I will be following your instruction this week end. The good news, I live in the country on an acre so no problems. . .I have all my Camaro parts along side the shop in the back!
Re: Gas Guage Failure. . .How to fix
Ok, I appreciate the fuel gauge test procedure, but I have one question. First of all, let me say that with two different sending units, with the float all the way UP, my gauge barely reaches half.
Now, when I disconnect the sending unit wire from the plug in the trunk, and turn the key on, the gauge goes WAY past full. The needle goes around so far that it is horizontal. Is it supposed to go that far, or would you say my gauge has had it?
I hope one of you can help me.
Thanks,
Chris
Ok, I appreciate the fuel gauge test procedure, but I have one question. First of all, let me say that with two different sending units, with the float all the way UP, my gauge barely reaches half.
Now, when I disconnect the sending unit wire from the plug in the trunk, and turn the key on, the gauge goes WAY past full. The needle goes around so far that it is horizontal. Is it supposed to go that far, or would you say my gauge has had it?
I hope one of you can help me.
Thanks,
Chris
Re: Gas Guage Failure. . .How to fix
What year and style of gauge?
If 1969 - located in right dash pod - yes and if your test resolve that it goes the same way past empty you can reset the pointer if the ohms are correct for half a tank of fuel = 45-ish.
If not the resistor on the rear of the gauge maybe damaged.
What year and style of gauge?
If 1969 - located in right dash pod - yes and if your test resolve that it goes the same way past empty you can reset the pointer if the ohms are correct for half a tank of fuel = 45-ish.
If not the resistor on the rear of the gauge maybe damaged.
Re: Gas Guage Failure. . .How to fix
the guage on my 67 camaro goes from 8 o'clock (empty) to 12 o'clock (full) when unplugged the wire in boot guage sits on full mark perfectly tested the sender seems to work fine filled the tank and i got 91 ohms, so would this be a resistor problem? or is the guage niddle in the wrong spot?
how and where is this resistor?
thanks
the guage on my 67 camaro goes from 8 o'clock (empty) to 12 o'clock (full) when unplugged the wire in boot guage sits on full mark perfectly tested the sender seems to work fine filled the tank and i got 91 ohms, so would this be a resistor problem? or is the guage niddle in the wrong spot?
how and where is this resistor?
thanks
Re: Gas Guage Failure. . .How to fix
Chris,
The sender float just "stops" at the full range, but the arm can stick if too much fuel pushes on it long enough.
Bench test the sender laying in the trunk and see if as you manipulate the float you get a change in ohm's from it. If you don't take a good look at the electronic portion of the float arm assembly for loose or missing parts. Once you can get it to report a full range on your meter hook it up to the gauge harness connection in the trunk and ground the sender to the decklid latch catch near the connection. Move the float and see if the gauge reacts.
If it does you can either drain the tank or drive it bone dry, and swap out the unit, then bench test the unit that was inside the tank and see if you can get a working spare out of it.
Chris,
The sender float just "stops" at the full range, but the arm can stick if too much fuel pushes on it long enough.
Bench test the sender laying in the trunk and see if as you manipulate the float you get a change in ohm's from it. If you don't take a good look at the electronic portion of the float arm assembly for loose or missing parts. Once you can get it to report a full range on your meter hook it up to the gauge harness connection in the trunk and ground the sender to the decklid latch catch near the connection. Move the float and see if the gauge reacts.
If it does you can either drain the tank or drive it bone dry, and swap out the unit, then bench test the unit that was inside the tank and see if you can get a working spare out of it.
Re: Gas Guage Failure. . .How to fix
I just found this:
The wire that needs power on it is the other wire on the dash unit, and it should have power when the key is on. If it does, and the gauge doesn't read upscale, temporarily ground the wire that goes back to the sender, and briefly turn on the key. If the gauge responds by moving upscale in slow jerks until it gets up toward "full" on the gauge, the dash unit and the gauge regulator is OK, and your problem is associated with the sender in the tank. DO NOT LEAVE THAT WIRE GROUNDED for more than the time it takes to see if the dash unit responds - immediately turn OFF the key and remove the temporary ground before you turn the key on again. Failing to do that can burn out the dash unit.
Is this telling me that there is a voltage regulator that could be bad, rather than the gauge? If I bought a repro gauge, does it have all that is necessary to make stuff work, as long as the sending unit and wiring is all ok?
I just found this:
The wire that needs power on it is the other wire on the dash unit, and it should have power when the key is on. If it does, and the gauge doesn't read upscale, temporarily ground the wire that goes back to the sender, and briefly turn on the key. If the gauge responds by moving upscale in slow jerks until it gets up toward "full" on the gauge, the dash unit and the gauge regulator is OK, and your problem is associated with the sender in the tank. DO NOT LEAVE THAT WIRE GROUNDED for more than the time it takes to see if the dash unit responds - immediately turn OFF the key and remove the temporary ground before you turn the key on again. Failing to do that can burn out the dash unit.
Is this telling me that there is a voltage regulator that could be bad, rather than the gauge? If I bought a repro gauge, does it have all that is necessary to make stuff work, as long as the sending unit and wiring is all ok?
I am having the same problem on my 67 with console gauge. Went back to trunk and unplugged the sender. Grounded the wire to the gauge at the trunk plug got empty on the gauge. With the wire unplugged in the trunk I get full. Put a 40 ohm resister on the wire in the trunk got little under 1/2 on the gauge. Put a 10 ohm resister on the wire in the trunk got almost empty. I have to assume its the sender. Stuck a dowel rod down the fill port by my license plate but could not seam to find the sending unit with the dowel rod to see if it was stuck. Do you have to remove the fill neck in the trunk to use the dowel?
John
John
John - The 69 it is a straight shot to see the float from the filler neck. 67-68 it is not easy if at all possible to manipulate the float from the filler neck. I think others have accomplished that but don't know if dis-assembly was required.
But I think at this point the next test would be to connect an alligator clip test lead, or create a long test lead and connect one end to your sender's ground wire connection at the strap and shunt the other end to a known good ground, or the trunk latch and see if the gauge comes alive. If not I would be feeling confident if I drained and dropped the tank it would not be a waste of time. The sender does seem to the the issue - but it might just be the ground. If not you can remove the sender and bench test it.
But I think at this point the next test would be to connect an alligator clip test lead, or create a long test lead and connect one end to your sender's ground wire connection at the strap and shunt the other end to a known good ground, or the trunk latch and see if the gauge comes alive. If not I would be feeling confident if I drained and dropped the tank it would not be a waste of time. The sender does seem to the the issue - but it might just be the ground. If not you can remove the sender and bench test it.
Brian
Good advice!
I forgot to say I did run a wire from the tank ground wire to another ground location with no change. I also forgot to say that when I unplug the trunk plug to the sender and measure resistance to ground it is always 90 ohms or so. I used my ohm meter on the sender while trying to get at the sender with the dowel. Figured if I touched the sender with the dowel that I should see a change in ohms on my meter. No luck there!
John
Good advice!
I forgot to say I did run a wire from the tank ground wire to another ground location with no change. I also forgot to say that when I unplug the trunk plug to the sender and measure resistance to ground it is always 90 ohms or so. I used my ohm meter on the sender while trying to get at the sender with the dowel. Figured if I touched the sender with the dowel that I should see a change in ohms on my meter. No luck there!
John
Guys, I have a similar problem with my 69 with console gauges. Using the troubleshooting guide noted here (along with some good advice) it looks like it is my sending unit because I get about 135 ohms at the trunk connection; the tan wire.
The question I have now is: what would cause the gauge to go past full when I turn off the ignition? Based on the troubleshooting, that would lead me to believe that the tan wire is grounding out somewhere between the lead in the trunk back to the sending unit.
Am I way off here? I am waiting on a new sending unit to arrive and to use up the gas so I can drop the tank, I suppose that when I do that, I'll be able to tell if the tan wire is in good shape.
The question I have now is: what would cause the gauge to go past full when I turn off the ignition? Based on the troubleshooting, that would lead me to believe that the tan wire is grounding out somewhere between the lead in the trunk back to the sending unit.
Am I way off here? I am waiting on a new sending unit to arrive and to use up the gas so I can drop the tank, I suppose that when I do that, I'll be able to tell if the tan wire is in good shape.
Bill,
Not sure I understand your problem but from my test 135 ohms would make your gauge go past full I think. Go to radio shack and buy a 10 ohm a 40 or 50 ohm and a 100 ohm and try them one at a time on the tan wire in the trunk. One end of the resistor needs to be grounded. If you get 1/8 tank on the 10 ohm 1/2 tank on the 50 ohm and full on the 100 ohm then its your sender.
I assume you tried to ground the tan lead and get empty.
I am thinking about making a box with a 3 position switch with the resistors in it. The box would just plug into the trunk plug and then this test would be easy.
John
Not sure I understand your problem but from my test 135 ohms would make your gauge go past full I think. Go to radio shack and buy a 10 ohm a 40 or 50 ohm and a 100 ohm and try them one at a time on the tan wire in the trunk. One end of the resistor needs to be grounded. If you get 1/8 tank on the 10 ohm 1/2 tank on the 50 ohm and full on the 100 ohm then its your sender.
I assume you tried to ground the tan lead and get empty.
I am thinking about making a box with a 3 position switch with the resistors in it. The box would just plug into the trunk plug and then this test would be easy.
John
Bill, if the tan wire was grounded, gauge would show empty.
Siphon out or use some fuel, then see where the needle points.
Reading 135 ohms means there is a good circuit from the tan wire through the s/unit to ground - extremely full tank.
As far as the needle going past full after ign turned off, gravity affecting the needle? It is on the right side of the gauge. If you have a half tank and park the Camaro on an embankment drvr side down, does the needle 'fall' to the drvr side?
Siphon out or use some fuel, then see where the needle points.
Reading 135 ohms means there is a good circuit from the tan wire through the s/unit to ground - extremely full tank.
As far as the needle going past full after ign turned off, gravity affecting the needle? It is on the right side of the gauge. If you have a half tank and park the Camaro on an embankment drvr side down, does the needle 'fall' to the drvr side?
Thanks John, I guess my question is, what would make the gauge creep past full when I shut off the car instead of going to E or just below E.
When I did the test as written in the sticky, disconnecting tan wire - gauge goes past full, then grounding the harness where the tan wire connects - gauge goes past empty, I got those results.
When I checked the ohms on the tan wire I got about 135, hence the assumption that the sending unit has failed. The fact that the gauge doesn't go to E or below E when there is no power, is driving me nuts.
Anyhow, thanks again for your time. Don't know what I'd do without these forums since I'm new to Camaros, I used to have a 66 Chevelle, am really familiar with the 67 Chevelle too, but the Camaro is a different beast.
When I did the test as written in the sticky, disconnecting tan wire - gauge goes past full, then grounding the harness where the tan wire connects - gauge goes past empty, I got those results.
When I checked the ohms on the tan wire I got about 135, hence the assumption that the sending unit has failed. The fact that the gauge doesn't go to E or below E when there is no power, is driving me nuts.
Anyhow, thanks again for your time. Don't know what I'd do without these forums since I'm new to Camaros, I used to have a 66 Chevelle, am really familiar with the 67 Chevelle too, but the Camaro is a different beast.
The biggest pain in dropping the tank is emptying it. The rest is okay, better with a second set of hands. I'm about to drop my own tank because the sender currently in the tank is missing the return line so the original owner just capped it at the rail with a couple clamps at either end of a section of rubber hose and a screw. Old school fix for sure. Of course my tank is almost full so I may wait until its empty before I replace the sender just to avoid the fuel storage issue.
I have a few questions.
On a 68 console gas gauge. When you turn off the key...should the needle fall all the way to empty?
What happens if you manually move the needle with your finger?
The reason I'm asking is I had a wiring disaster yesterday and now my gas gauge is working differently or not working at all. Plus the fuel light came on but I'm nowhere close to empty. It went off again though.
This is what brought this up:
"I had bad scare today. I was asked what my "batt" gauge reads and to be honest, I have never seen it move since I've owned the car. I decided to take apart the console and inspect the connections. Low and behold, didn't think to disconnect the battery. When I loosened up the nuts on the batt gauge I saw a spark. Then I saw a puff of smoke in the wiring harness. Holy crap! Quickly disconnected the battery and inspected the harness. Didn't see any damage. Rechecked all connections. Reconnected the battery cables. Turned the key and my batt gauge moved! In the neg before starting the car...in the pos after starting the car. Cool!
Now the bad news...all of the sudden I see a ton of smoke coming from the harness and the shifter light bulbs on. No NO NO!!! Run and disconnect the battery. Inspect the harness and the GND wire (from the shifter to the shifter lights and the sawtooth gauge pod) melted and actually caused the wire to break at one point. Oh my God...
Well after some severe depression, total fear and self-loathing... I cut the wrapping from the harness to inspect. It APPEARS that only the GND wire had any damage. All of the GND wire sheathing was melted. I cut out all GND wire and made up a new GND distribution modeled after the original. It's funny how the original was part of the harness but does not go thru the connector where all the other wiring does. Checked all connections again and then connected the battery. No smoke. Watched all the gauges move as before...including the BATT.
Then strangely...my FUEL light went on in the dash...but I'm not empty. I notice now my gas gauge stopped moving. Damn it. Any ideas?
This is why I stay away from electrical stuff."
Wondering if I damaged the gauge or the resistor.
On a 68 console gas gauge. When you turn off the key...should the needle fall all the way to empty?
What happens if you manually move the needle with your finger?
The reason I'm asking is I had a wiring disaster yesterday and now my gas gauge is working differently or not working at all. Plus the fuel light came on but I'm nowhere close to empty. It went off again though.
This is what brought this up:
"I had bad scare today. I was asked what my "batt" gauge reads and to be honest, I have never seen it move since I've owned the car. I decided to take apart the console and inspect the connections. Low and behold, didn't think to disconnect the battery. When I loosened up the nuts on the batt gauge I saw a spark. Then I saw a puff of smoke in the wiring harness. Holy crap! Quickly disconnected the battery and inspected the harness. Didn't see any damage. Rechecked all connections. Reconnected the battery cables. Turned the key and my batt gauge moved! In the neg before starting the car...in the pos after starting the car. Cool!
Now the bad news...all of the sudden I see a ton of smoke coming from the harness and the shifter light bulbs on. No NO NO!!! Run and disconnect the battery. Inspect the harness and the GND wire (from the shifter to the shifter lights and the sawtooth gauge pod) melted and actually caused the wire to break at one point. Oh my God...
Well after some severe depression, total fear and self-loathing... I cut the wrapping from the harness to inspect. It APPEARS that only the GND wire had any damage. All of the GND wire sheathing was melted. I cut out all GND wire and made up a new GND distribution modeled after the original. It's funny how the original was part of the harness but does not go thru the connector where all the other wiring does. Checked all connections again and then connected the battery. No smoke. Watched all the gauges move as before...including the BATT.
Then strangely...my FUEL light went on in the dash...but I'm not empty. I notice now my gas gauge stopped moving. Damn it. Any ideas?
This is why I stay away from electrical stuff."
Wondering if I damaged the gauge or the resistor.
Wow well you may have toasted a fusible link down wind.
It does sounds like the LFWM - Low Fuel Warning Module is toast since it reads line Ohms to trigger the light and unless your tank sender is sending below the trigger point you shouldn't see it. Test the Ohms from the fuel sender and post that value. The gauge should match. The original resisters were just thin wire wound around the carrier and the wire is very fragile these days. Broken wire will result in wrong reading on the gauge. But we will understand more once you post the ohms reading you are getting from the sender.
The needle doesn't always move around without power, gravity sometimes will pull it one way or the other. If you move the needle with you finger and the power is on the needle should return to the reported value from the sender signal.
Rule 23 always have a 1-2-3 dry extinguisher in the car.
It does sounds like the LFWM - Low Fuel Warning Module is toast since it reads line Ohms to trigger the light and unless your tank sender is sending below the trigger point you shouldn't see it. Test the Ohms from the fuel sender and post that value. The gauge should match. The original resisters were just thin wire wound around the carrier and the wire is very fragile these days. Broken wire will result in wrong reading on the gauge. But we will understand more once you post the ohms reading you are getting from the sender.
The needle doesn't always move around without power, gravity sometimes will pull it one way or the other. If you move the needle with you finger and the power is on the needle should return to the reported value from the sender signal.
Rule 23 always have a 1-2-3 dry extinguisher in the car.
Okay...nevermind last post.
I disconnected the brown wire from the trunk pan. Turned the key in the ignition...Needle rises to past the F on the gauge.
Question...what happens if you GND the loose lead going to the sender? I screwed up and did that first. I seem to be my own worst enemy the last few days.
I then GNDed the brown wire on the harness side and the needle went to E...but not past it.
I checked with the multi-meter set at 200 Ohm across the two wires (still disconnected)
The reading was 111.7
I disconnected the brown wire from the trunk pan. Turned the key in the ignition...Needle rises to past the F on the gauge.
Question...what happens if you GND the loose lead going to the sender? I screwed up and did that first. I seem to be my own worst enemy the last few days.
I then GNDed the brown wire on the harness side and the needle went to E...but not past it.
I checked with the multi-meter set at 200 Ohm across the two wires (still disconnected)
The reading was 111.7
111 is way too high and should then read past full. If that is correct the LFWM should not be activating.
You were reading the loose connector-wire and not the receptacle that goes forward to the gauge right?
Sounds like the resistor is or the gauge is bad. Also run the Ohm's meter over through the two leads of just the resistor and post a picture of the resistor or describe the unit.
You were reading the loose connector-wire and not the receptacle that goes forward to the gauge right?
Sounds like the resistor is or the gauge is bad. Also run the Ohm's meter over through the two leads of just the resistor and post a picture of the resistor or describe the unit.
Everything sounds good so far - have you checked the sending unit ground wire. Will be near the front of the passenger's gas tank strap
Good troubleshooting guide a couple of posts down here: http://www.chevelles.com/forums/showthread.php?t=53519
Good troubleshooting guide a couple of posts down here: http://www.chevelles.com/forums/showthread.php?t=53519
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