Fuel gage bounces
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
OK I must have dreamed that because I just opened a gauge up and there was "no" string packing around the center axle. 
Inside was the center axle with a wheel attached to it. The wheel was in a bath of thin grease. That must be the dampening that keeps the needle from moving too fast.
The fuel gauge was not a vette gauge but was a GM.
Where is Willcox ???
I'm reading this from top to bottom and will comment as I go along.
Below you'll see a picture of how most small gauges operate. The fluid inside the gauge can dry out and the gauge will lose its dampening ability. When this happens the needle will usually follow the movement of the float in the tank.
I’ve tested this repeatedly with good sending units and gauges; the gauge will not follow the sending unit. What I’ve not tested is a good gauge with a defective sending unit! I’ve never had a reason to until now, but I think Roger may have done so in another post in this thread. If Roger has not done this, it will give me a new project to test.
Willcox
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
This video was posted by Buns on the C2 fourm a long time ago... Just more info. Here is the thread link. http://forums.corvetteforum.com/c1-a...-squirely.html
18243
18243
Last edited by Willcox Corvette; Sep 5, 2009 at 01:57 PM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
OK I found something. I set a gauge up and using the pot setup Ernie sent me I set the needle to 1/2 tank- full power on the 12 volts in to the gauge-- full and solid ground to the gauge cluster
Then I removed the ground (same as the ground to the tank) and put a pot in between the gauge and ground so I could vary the ground.
I then rotated the ground pot up to 50 ohms-this only changed the needle by 1/8 tank so this wont effect the accuracy too bad.
Then using the first pot that varys the input to the gauge (what comes from the tank sender) I started rotating it back and forth to make the needle go from E to F.
With the resistance up on the ground side the speed of the needle is much much slower.
To me this means a poor ground at the tank sender can mask a bad gauge."Bad" gauge from the standpoint of dampening even though it reads accurately.
My thoughts are Noonies gauge has poor dampening capability's but probably reads accurately sitting still but when he soldered the ground in made a better connection to ground and increased the sensitivity of the gauge movement.
Then I removed the ground (same as the ground to the tank) and put a pot in between the gauge and ground so I could vary the ground.
I then rotated the ground pot up to 50 ohms-this only changed the needle by 1/8 tank so this wont effect the accuracy too bad.
Then using the first pot that varys the input to the gauge (what comes from the tank sender) I started rotating it back and forth to make the needle go from E to F.
With the resistance up on the ground side the speed of the needle is much much slower.
To me this means a poor ground at the tank sender can mask a bad gauge."Bad" gauge from the standpoint of dampening even though it reads accurately.
My thoughts are Noonies gauge has poor dampening capability's but probably reads accurately sitting still but when he soldered the ground in made a better connection to ground and increased the sensitivity of the gauge movement.
If you have the dash unit out of the car, you should be able to test the dash unit. You seem to have the knowledge and the proper testing items.
I would power up the gauge and use the linear potentiometer as my sending unit. This way you can make quick swings with the turn of a ****. See if the gauge jumps quickly when doing this and if the gauge responds just like it does in the dash then the gauge is the problem
As with Noonie’s posted problem and Rogers findings, I believe the coalition between repairing the ground to the tank and the dash gauge failure are related. Since Rogers findings on adding resistance to the ground only slows the movement of the dash unit.
In the mid year thread I posted a link to there was discussion about adding a capacitor inline to dampen the needle, I believe it was a 100 volt 2000 MF capacitor. While I’m not saying this would or would not work, it would be a PITA.
As most can see from the length of this tread, this problem is not just C3 specific and has been an ongoing problem with these cars for years.
Willcox Inc.
W
Last edited by Willcox Corvette; Sep 5, 2009 at 01:56 PM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
OK I must have dreamed that because I just opened a gauge up and there was "no" string packing around the center axle. Inside was the center axle with a wheel attached to it. The wheel was in a bath of thin grease. That must be the dampening that keeps the needle from moving too fast.
The fuel gauge was not a vette gauge but was a GM.
Where is Willcox ???
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
No you don't..... They are a pain!
It took me 5 hours to do the vid on the tach boards.
Now I have editing software and got some tips from someone else on doing them in burst. This allows you to put them together in one video and edit out the mistakes.
On the tach video... if I screwed up, I would start over, and over and over, and over, and over....
OH... Just a tid bit of info on the tachometers too! If the oil is missing from the 1975-1982 tachometers, when you hold the tach in your hand the needle will pretty much free wheel. If you tilt it backwards, it will float. If you flick the needle with your finger it just flips around. We had one of these the other day! It would read high at ever point on the board when installed, no matter what you did to it. (no resistance). On the bench it would show working fine, but in the car it would just go crazy. We replaced the metal can and inner works with a good used one and the tach worked fine after that. If you have this condition, you're in trouble.
E
It took me 5 hours to do the vid on the tach boards.
Now I have editing software and got some tips from someone else on doing them in burst. This allows you to put them together in one video and edit out the mistakes.
On the tach video... if I screwed up, I would start over, and over and over, and over, and over....
OH... Just a tid bit of info on the tachometers too! If the oil is missing from the 1975-1982 tachometers, when you hold the tach in your hand the needle will pretty much free wheel. If you tilt it backwards, it will float. If you flick the needle with your finger it just flips around. We had one of these the other day! It would read high at ever point on the board when installed, no matter what you did to it. (no resistance). On the bench it would show working fine, but in the car it would just go crazy. We replaced the metal can and inner works with a good used one and the tach worked fine after that. If you have this condition, you're in trouble.
E
Last edited by Willcox Corvette; Sep 5, 2009 at 03:08 PM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
No you don't..... They are a pain!
It took me 5 hours to do the vid on the tach boards.
Now I have editing software and got some tips from someone else on doing them in burst. This allows you to put them together in one video and edit out the mistakes.
On the tach video... if I screwed up, I would start over, and over and over, and over, and over....
OH... Just a tid bit of info on the tachometers too! If the oil is missing from the 1975-1982 tachometers, when you hold the tach in your hand the needle will pretty much free wheel. If you tilt it backwards, it will float. If you flick the needle with your finger it just flips around. We had one of these the other day! It would read high at ever point on the board no matter what you did to it. (no resistance). If you have this condition, you're in trouble.
E
It took me 5 hours to do the vid on the tach boards.
Now I have editing software and got some tips from someone else on doing them in burst. This allows you to put them together in one video and edit out the mistakes.
On the tach video... if I screwed up, I would start over, and over and over, and over, and over....
OH... Just a tid bit of info on the tachometers too! If the oil is missing from the 1975-1982 tachometers, when you hold the tach in your hand the needle will pretty much free wheel. If you tilt it backwards, it will float. If you flick the needle with your finger it just flips around. We had one of these the other day! It would read high at ever point on the board no matter what you did to it. (no resistance). If you have this condition, you're in trouble.
E
Your talking much more today,sounds like your feeling better. 
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Roger,
Thanks.... it comes and goes right now.... (Pinched nerve guys) Last night horrible, this morning not so bad.
W
Thanks.... it comes and goes right now.... (Pinched nerve guys) Last night horrible, this morning not so bad.
W
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Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Well with all the help from Willcox and DWncchs on testing the fuel gauge and fuel sending unit to determine what was causing the fuel neddle to bounce. I replaced the sending unit and 
it's working great. Thanks again 
ED
from Willcox and DWncchs on testing the fuel gauge and fuel sending unit to determine what was causing the fuel neddle to bounce. I replaced the sending unit and it's working great. Thanks again ED
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
I had one today in a 70 that was doing the same thing. I replaced the gauge with a good used one and it doesn't fluctuate now while driving. This good used gauge you could actually feel the dampening resistance in comparison to the new or even the supposed rebuilt gauge.
I'm going to start gathering up good used gauges.
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
The video that Ernie posted is exactly how it should work. If I had a camera I could have made the same video using the 70 I was working on. The reaction of the needle from the sender must be heavily delayed.
I have not yet gotten hold of my electronics buddy to see if there is such a thing that could be put on the sender wire to "choke" , slow down or retard the ohms signal before it gets to the gauge.
Race Director
Joined: May 2006
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From: Dayton, Ohio
Noonie ... what part of Florida do you live in ? I have a couple good used gauges and I will be in Fort Myers Jan-Apr , I could leave one with you for awhile and you could try it and see if it takes care of your bouncing so you dont have to invest in one. Both are not pretty but work as they are supposed to and will be good for testing.
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Sorry.... I guess its going to depend on the individual car. Before ED posted I was going to say if a dash gauge passes the test of unplugging the sender wire and needle going to full and grounding the sender wire and the needle goes to empty the next test would be to watch the needle speed. If the needle moves any faster full scale than 2 full seconds the bounce is in the gauge. The gauge I put in today would not flick or bounce no matter what I did with any of the wires. It was very sslloooooooowwwwww. Before with the rebuilt gauge and the new gauge I could shake the car and the needle would bounce all over the place until the fuel in the tank settled. I did test the sender and its ohms reading were very smooth up and down the scale.
The video that Ernie posted is exactly how it should work. If I had a camera I could have made the same video using the 70 I was working on. The reaction of the needle from the sender must be heavily delayed.
I have not yet gotten hold of my electronics buddy to see if there is such a thing that could be put on the sender wire to "choke" , slow down or retard the ohms signal before it gets to the gauge.
The video that Ernie posted is exactly how it should work. If I had a camera I could have made the same video using the 70 I was working on. The reaction of the needle from the sender must be heavily delayed.
I have not yet gotten hold of my electronics buddy to see if there is such a thing that could be put on the sender wire to "choke" , slow down or retard the ohms signal before it gets to the gauge.
After reading your last thread I remember while doing your above suggestions, the needle did go fast to full and fast to empty, with no lapse in time.
Anyway there is a fuel gauge enroute as I write. Maybe with the position I had the gauge laying around repositioned
this oil filler in the gauge and made it work for awhile
Will let you know next about the gauge!! Thanks DWncchs--ED
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Ed-
If you want to send me the original gauge I can test it for you before you purchase the new gauge. It may be to late. . . It only takes me a few minutes and I can immolate a swashing take with the test machine.
Let me know.
Willcox
If you want to send me the original gauge I can test it for you before you purchase the new gauge. It may be to late. . . It only takes me a few minutes and I can immolate a swashing take with the test machine.
Let me know.
Willcox
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Mr Willcox I will take you up on your offer, It will be the first of the week before I can mail. Thanks again ED79
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
No problem Ed, I highly think the problem is in the dash unit...
Send it to:
Willcox Inc.
Service Department.
123 E. Maple Street
Jeffersonville, Indiana 47130.
Willcox
Send it to:
Willcox Inc.
Service Department.
123 E. Maple Street
Jeffersonville, Indiana 47130.
Willcox
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Now you made me look at my gage!
Mr Willcox:
#1 Get well fast, you are a real trooper, not feeling 100% but you still find the time to help us out. Thank You!
#2 Thanks to your service and shipping department for getting the parts that I needed to keep my 74 clunker on the road.
#3 All this talk about bouncing fuel gauges made me look at mine. At between 1/4 and 1/2 a tank mine bounces too, it ain't bad enough for me to need a new one. I fill it up and it reads OK for the next 130 miles.
PG.
#1 Get well fast, you are a real trooper, not feeling 100% but you still find the time to help us out. Thank You!
#2 Thanks to your service and shipping department for getting the parts that I needed to keep my 74 clunker on the road.
#3 All this talk about bouncing fuel gauges made me look at mine. At between 1/4 and 1/2 a tank mine bounces too, it ain't bad enough for me to need a new one. I fill it up and it reads OK for the next 130 miles.
PG.
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
OK With the dash out I installed a new AC Delco gauge, plugged it up to instrument panel wiring harness and fuel gauge goes to 5/8 to 3/4 tank.....I only have a 1/4 tank of fuel, now what's the deal
Unplugged sending unit and needle slowly went to 3 o'clock, grounded sending unit wire and needle slowly went to empty, plugged sending unit back up and it goes to 3/4. I'm about ready to light a match 
With the dash out I installed a new AC Delco gauge, plugged it up to instrument panel wiring harness and fuel gauge goes to 5/8 to 3/4 tank.....I only have a 1/4 tank of fuel, now what's the deal Unplugged sending unit and needle slowly went to 3 o'clock, grounded sending unit wire and needle slowly went to empty, plugged sending unit back up and it goes to 3/4. I'm about ready to light a match
Race Director
Joined: May 2006
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From: Dayton, Ohio
First did you get the resitor put back with all the fiber washers in the right places ?
2nd take a deep breath set your pot to 45 ohms and connnect 1 wire to ground and the other to the sender wire and see if the gauge reads 1/2.
3rd - you say you have 1/4 tank- read your sender with your ohm meter-should be around 22 ohms
edit- I forgot ,does your new gauge need the resistor ?
2nd take a deep breath set your pot to 45 ohms and connnect 1 wire to ground and the other to the sender wire and see if the gauge reads 1/2.
3rd - you say you have 1/4 tank- read your sender with your ohm meter-should be around 22 ohms
edit- I forgot ,does your new gauge need the resistor ?