Slant Six Forum :: Gas tank sending unit doesn't work

Before installing the unit since it's a pain to put it in and take it back out again... I would pull the unit, visually look at the 'lever' and the measuring unit and make sure as you 'sweep' the float up and down the contacts are clean and close enough to 'register'... another thing to do similar to your experience, it to connect the sending unit to it's connection under the car, use a length of wire and a couple of alligator clips to clip to the unit body and a clean ground on the under side of the car... have your wife click the ignition to 'on'/no start and sweep the float arm up and down... if it still doesn't register check ground, check the arm... hopefully it's just the ground and not the measuring arm/needle (have had a unit that worked fine, pulled it out cleaned out tank, and then the needle decided to fall out due to corrosion...also have seen the 'contacts' get corroded and break too)...

-D.Idiot

What else could cause my dash to not register?

I plugged my store bought wire coming from the sending unit into the blue terminal. I plugged the wire into the section of the plug that goes under the dash (and not the section that goes to the rear of the car under the carpet). Turn on the ignition, still no movement on the fuel gauge.

We took a four inch section of copper wire ... and hooked it to the sending unit nipple. ... and plugged in the other end of that four inch wire to the blue wire on the upstream terminal, ...turned key on, and damned if that &*$#^@ fuel gauge began moving as we moved the float back and forth on the sending unit.

Once I grounded the sending unit at the kickpanel wiring harness, it has been moving every time since then.

Author:	74DartSport [ Mon Apr 21, 2008 9:57 am ]
Post subject:	Gas tank sending unit doesn't work
I clear coated my new gas tank this weekend. The sending unit is the original installed in 1974. It has a new float and filter. As of now it has no fuel in the tank. After the clear dried, I turned the tank upside down and could feel the float move to the TOP of the tank. I then plugged the electrical line under the car to the nipple on the tank and attached the ground strap to the fuel line coming out of the sending unit/gas tank. I had my wife turn the car ignition on (without starting the car) and the fuel gauge on the dash did not move. Do I have a bad sending unit? My multimeter showed I have power at the electrical line that attaches to the tank nipple. What else should I test before putting gas in the tank?

Author:	DusterIdiot [ Mon Apr 21, 2008 10:17 am ]
Post subject:	Out of tank check...
Before installing the unit since it's a pain to put it in and take it back out again... I would pull the unit, visually look at the 'lever' and the measuring unit and make sure as you 'sweep' the float up and down the contacts are clean and close enough to 'register'... another thing to do similar to yoour experience, it to connect the sending unit to it's connection under the car, use a length of wire and a couple of alligator clips to clip to the unit body and a clean ground on the under side of the car... have your wife click the ignition to 'on'/no start and sweep the float arm up and down... if it still doesn't register check ground, check the arm... hopefully it's just the ground and not the measuring arm/needle (have had a unit that worked fine, pulled it out cleaned out tank, and then the needle decided to fall out due to corrosion...also have seen the 'contacts' get corroded and break too)... -D.Idiot

Author:	emsvitil [ Mon Apr 21, 2008 1:16 pm ]
Post subject:
Upside down, the sending unit will go 'up' farther than it ever would achieve with a full tank.. It might just be that it's so far 'up' that it's out of the resistor contact in the unit.

Author:	69a100 [ Tue Apr 22, 2008 8:39 am ]
Post subject:
Make sure that the unit has excellent ground!!!!!!!!!

Author:	74DartSport [ Thu Apr 24, 2008 3:27 pm ]
Post subject:	Re: Out of tank check...
Quote: Before installing the unit since it's a pain to put it in and take it back out again... I would pull the unit, visually look at the 'lever' and the measuring unit and make sure as you 'sweep' the float up and down the contacts are clean and close enough to 'register'... another thing to do similar to your experience, it to connect the sending unit to it's connection under the car, use a length of wire and a couple of alligator clips to clip to the unit body and a clean ground on the under side of the car... have your wife click the ignition to 'on'/no start and sweep the float arm up and down... if it still doesn't register check ground, check the arm... hopefully it's just the ground and not the measuring arm/needle (have had a unit that worked fine, pulled it out cleaned out tank, and then the needle decided to fall out due to corrosion...also have seen the 'contacts' get corroded and break too)... -D.Idiot Last night I hooked up the unit without putting it in the gas tank, grounded it using the original grounding strap, and grounded it again using a good length of copper wiring. Still no go on the dashboard. The unit has three tabs that I bent upwards with a flathead screwdriver and took the cover off to reveal the contact area on the lever was actually touching the contact area. It was. So I took my multimeter, set it on 20 ohms, started with a reading of 1 and touched the positive end of the red multimeter wire on the nipple which sticks out of the fuel tank and touched the black multimeter wire on the end of the wire that goes into the cover. The 1 went to 0 as it should. Then I touched the black wire to the contact area inside the cover (the area where the measuring arm actually sweeps in a semi-arch movement as the float moves up and down depending on level of gas in tank). The 1 went down to 0.07 or 0.04 depending on the area I touched. It never went to 0.00. Is the unit good or bad? A new unit is $100.00 at Advance Auto. Should I bite the bullet and buy a new one? What else could cause my dash to not register?

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Gas tank sending unit doesn't work https://slantsix.org/forum/viewtopic.php?t=28500	Page 1 of 1

Author:	DusterIdiot [ Thu Apr 24, 2008 3:50 pm ]
Post subject:	Ooof....
Quote: What else could cause my dash to not register? The gauge can be bad...the leads on the circuit board can be tarnished or 'broke'... and the last thing is the wire going from the unit, to the trunk, under your carpet (under the rear seat/driver's seat) just beside the driver's side door sills in a bundle, and up the driver's side kick panel to the underdash harness can be bad... (I had this happen in the Beater Valiant, and went with an aftermarket gauge and rewired the lead since I could not find the elusive 'short' in the harness and after I replaced the sending unit...which also was bad...) Welcome electrical mayhem 400/500.. the needle in the needle in the haystack... -D.Idiot

Author:	65Dodge100 [ Fri Apr 25, 2008 10:29 am ]
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Author:	Chuck [ Mon Apr 28, 2008 9:41 pm ]
Post subject:
Try some of the troubleshooting tips here.

Author:	74DartSport [ Wed May 07, 2008 2:59 pm ]
Post subject:
I finally broke down and bought a new sending unit. It cost $105.00, but I refuse to drive without a working fuel gauge. I have spent many hours on my back under the car with the sending unit wire plugged into the nipple on the old and new sending units. I have used the original ground strap and also a length of solid copper wire to ground the sending unit. Still no movement on the gas gauge after I turn on the ignition. (Ignition on, car not started.) Last week I bought six feet of wire. I wrapped one end of the wire around the nipple on the sending unit, ran the wire on the garage floor under the car, and plugged the other end of the wire into the wire harness behind the driver side kick panel. That plug has seven terminals that come from the back of the car. I disconnected the male plug from the female plug. I immediately identified four of the seven terminals (two that control the dome light and two that control the rear outer taillights). The wire at the nipple is blue, so one of the three unidentified terminals also had a blue wire coming under the carpet to the kickpanel terminal. Logically I plugged my store bought wire coming from the sending unit into the blue terminal. I plugged the wire into the section of the plug that goes under the dash (and not the section that goes to the rear of the car under the carpet). Turn on the ignition, still no movement on the fuel gauge. Now I'm am really frustrated. It's three a.m. I go to bed and fume about my problem. My son just came home from college. Last night he and I repeated the above steps. No movement on the gas gauge. I am now considering the Allpar modification to the regulator on the back of the instrument cluster. I have spent hours reading SlantSix posts on the fuel gauge and instrument cluster problems. I am beyond frustrated. The right hand side of the instrument cluster works fine (brake light and oil pressure light up). The turn signals work and so does the emergency flasher. All bulbs have been changed and two broken sockets that screw into the back of the cluster have been replaced. When I pull the headlights on, the lights on the cluster do not come on, nor does the high beam light. So we remove the instrument cluster and take a number two pencil eraser and clean every copper colored wire from the pins labeled A thru L to the end of the copper wiring. We put the cluster back in the dash, hook up the wires, and all those new 192 bulbs light up, including the high beam light. Now that my cluster lights work, why doesn't my gas gauge move? The left side of the cluster has the Alternator, Temperature, and Fuel Gauges. The Alternator moves slightly to discharge when I pull on the headlights or turn key to ignition. Is the fuel gauge really broken? My brilliant college son suggested we bring the new sending unit inside the car and plug it into the upstream side of the kick panel terminal. We took a four inch section of copper wire and crimped down a terminal on one end and hooked it to the sending unit nipple. We crimped down another terminal and plugged in the other end of that four inch wire to the blue wire on the upstream terminal, used the original sending unit ground strap to ground on the metal dash, turned key on, and damned if that &*$#^@ fuel gauge began moving as we moved the float back and forth on the sending unit. Forget Allpar modification for now. That blue wire under my carpet must have a break in it, and that should be easy to isolate. The door buzzer and the fasten seat belt lights don't work, but my seats are not in and I'll address this problem on another post. Thanks to all those that gave me suggestions how to resolve this problem. I love success.

Author:	65Dodge100 [ Wed May 07, 2008 4:18 pm ]
Post subject:
Quote: I plugged my store bought wire coming from the sending unit into the blue terminal. I plugged the wire into the section of the plug that goes under the dash (and not the section that goes to the rear of the car under the carpet). Turn on the ignition, still no movement on the fuel gauge. We took a four inch section of copper wire ... and hooked it to the sending unit nipple. ... and plugged in the other end of that four inch wire to the blue wire on the upstream terminal, ...turned key on, and damned if that &*$#^@ fuel gauge began moving as we moved the float back and forth on the sending unit. It sounds like the plug behind the kick panel isn't connecting. You could try a jumper wire bypassing the plugâ€” one end connected to the wire going to the tank, downstream from the plug, the other end where you hooked the sender last to the blue wire upstream from the plug. Danny

Author:	Chuck [ Wed May 07, 2008 9:33 pm ]
Post subject:
Testing that wire should be a piece of cake. If you have a meter with a "beeper" in it for continuity testing, just connect one side of the meter to ground and the other side to the disconnected kick panel plug, then ground the wire that connects to the tank at the sender. The meter should beep if the wire is good. If your meter doesn't have a beeper, you will have to watch the needle instead of listening for the tone. If bad, just run a replacement. I made a previous post on checking the gauge. In your case, if you ground the kick panel wire that goes up to the dash, the gauge should move.

Author:	74DartSport [ Thu May 08, 2008 1:59 pm ]
Post subject:
Thanks Chuck. I read and applied your previous post test. For whatever reason that fuel gauge would not work for the last two months I've been trying to get it to work, all the suggestions on this board have been tried, except the Allpar repair. I really think my problem can be isolated to one of the following. After the car was repainted, I had an undercoating applied to the underneath of the body. This same undercoating was dealer applied in 1974 when I bought the car. I completely removed the original undercoating when I started the restoration in late 2005. Well that undercoating was on my fuel lines and everywhere else under the body of the car. The wires that I used to ground the sending unit probably were not making a good ground. I used a wire wheel to grind all the undercoating off the metal fuel lines and then I used the original fuel ground strap. The new sending unit and gas tank are now reinstalled. When I turn the car to auxillary, the fuel gauge moves slightly, even thought the gas tank has no fuel in it. By tomorrow the tank will have fuel. I resisted buying a new sending unit. That decision was wrong. Even though I had the new sending unit for over two weeks, I still could not get that fuel gauge to move. Once I grounded the sending unit at the kickpanel wiring harness, it has been moving every time since then. I also believe the original ground clip provides a better ground than a lenght of wire. Remember this car last ran in 1990. Maybe it was just stuck.

Author:	Chuck [ Thu May 08, 2008 3:14 pm ]
Post subject:
Quote: Once I grounded the sending unit at the kickpanel wiring harness, it has been moving every time since then. My point exactly. My original post mentioned grounding the gauge at the back in the instrument panel. If that worked, the next place to test would be at that harness connector, then at the sender itself. If the grounding at the gauge made the gauge work, then the problem would not be there. You move back toward the sending unit, checking at each junction, until the gauge no longer works when grounding the wire. Then you know the problem is between where it worked and where it didn't. From reading your posts, I wasn't sure that you tried grounding at the gauge first. From what you just posted, it sounds like you skipped that check.

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