Fuel Gauge/sending unit |
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Old Man Army
Member Joined: 29 Nov. 2017 Location: Lexington, SC Status: Offline Points: 6 |
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Posted: 18 July 2018 at 1:27am |
I have a confession to make, I'm a CJ 3B owner who spends a lot of time looking at this page. My questions is, the fuel gauge reads 1/2 full when the tank is full. It reads empty at about half a tank and never reads full. I've never done electrical trouble shooting, where should I start?
Thanks, Andrew
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Stev
Member Sponsor Member Joined: 27 July 2016 Location: Cincinnati Status: Offline Points: 2383 |
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Old Man Army,
I would think that your sending unit float wire / rod needs to be bent downward - so that the float with cause the sending unit to read full when it is full. Also tell us what you like about the Cj2A Page. Stev
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Stev
1946 CJ2A Trail Jeep (The Saint), 1948 CJ2A Lefty Restored |
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Steelyard Blues
Member Joined: 09 Oct. 2017 Location: Reno, NV Status: Offline Points: 1482 |
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Make sure your gauge has a good ground. I replaced a sender and I still could not get it to read. I pulled the gage out and there was a lot of surface rust on the back of the dash where it mounted. I cleaned it up with sandpaper and reinstalled. Works fine now.
Micah
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1947 CJ2A 106327, Engine J109205, Tub 97077. Luzon Red
https://www.thecj2apage.com/forums/steelyard-blues_topic41024_post397981.html?KW=micah+movie#397981 1965 Johnson Furnace Company M416 #6-1577 |
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athawk11
Member Joined: 18 Jan. 2012 Location: Arvada,Colorado Status: Offline Points: 4145 |
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Is your CJ3B a 12 volt setup or 6 volt setup?
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1- 1946 CJ2A
2- 1949 CJ3A |
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Old Man Army
Member Joined: 29 Nov. 2017 Location: Lexington, SC Status: Offline Points: 6 |
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Stev,
That sounds like a good idea, thanks. I like the CJ 2A page because it has so much information and the owners are obviously passionate about their vehicles. Best regards, Andrew
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Old Man Army
Member Joined: 29 Nov. 2017 Location: Lexington, SC Status: Offline Points: 6 |
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Micah,
Thanks for your quick response. I wouldn't be surprised if that's not the problem. Now to figure out how to get in there to get the gauge out. Best regards, Andrew
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Old Man Army
Member Joined: 29 Nov. 2017 Location: Lexington, SC Status: Offline Points: 6 |
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I'm going to show how little I know, but I believe it's a 12 volt. It's a 1961 and it uses a regular car battery.
Thanks, Andrew
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Rus Curtis
Member Joined: 25 Mar. 2010 Location: Alabama Status: Offline Points: 1733 |
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Andrew,
You're not the only 3B owner that spends time over here! These guys have a lot of depth and have been at it a long time. Plus, a handful are owners to more than one model of jeep. Your 3B should have the cluster gauge and is most likely a 12V. The battery will tell you by either counting the holes on the top or printed somewhere on the labeling. A quick check with a voltmeter will also tell. I try to always go simple first. Your gauge reads something. It responds to sending unit input. The suggestion of checking your sending unit is where I'd start. In the past, I'd always like to bench check the gauge and sending unit using a battery. After connecting everything, I'd swing the float up and down to see if the gauge responds correctly. There are some adjustments you can do to the sending unit to improve its readings. After removing your seat you can pull the sending unit (cover the tank hole to keep debris out) and leave the wire connected and check the readings while moving the float. That will tell you a lot. There is some good info on the 3B page on this type gauge. I also couldn't find your jeep in the owners list. Consider contacting Derek to get your jeep added!
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Rus Curtis
Alabama 1954 CJ3B Bantam T3-C |
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athawk11
Member Joined: 18 Jan. 2012 Location: Arvada,Colorado Status: Offline Points: 4145 |
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A general rule is, you want to run a 12 volt gauge with a
12v tank sending unit…and a 6 volt gauge with a 6v sending unit. Thus my question about the vehicle
voltage. For example, if your 3b has a
6v setup and a prior owner installed a 12v sending unit, it might cause some issues
with how the gauge reads the information sent by the sending unit.
The sending unit is basically an adjustable resistor. There are more Ohms passing through the sending unit while the tank is empty, than when the tank is full. In your case, your gauge can reach ‘E’, so the electricity needed is there and the connections and power supply are probably working okay. Another good sign is the gauge reading actually does vary with the amount of fuel. So, you’re already in better shape many of us. The gauge or the sending unit could be failing, but I agree with the others. A small float rod adjustment on the sending unit is worth the effort. You might also discover a fuel-logged float or the rod is getting caught on something that won’t let it move all the way to the top of its travel. If all this looks good, this is what I would no next… While the sending unit is out, keep the wire connected at the center of the sending unit. Since the sending unit is no longer attached to the tank, it is no longer grounded, so we need to secure an additional wire to the top plate of the sending unit. Just wrap a piece of wire through one of the mounting holes. Now, attach the other end to something metal on the 3B. It doesn’t really matter what, but these connections on this wire need to be clean from rust or paint. You now should be able to turn on the key and move the float up and down while watching the gauge. Perhaps have a tub of water close by that can simulate a full tank and an empty tank. I can’t remember for sure, but a full tank holds around 5-6” of fuel when full. Now, some trial and error. Depending on the float, it might have some adjustability built into it. If not, slight bends to the rod will adjust the float height when in contact with fluid. One Caution: DO NOT leave your key in the “on” position for long periods of time. While in the trial and error phase, TURN THE KEY OFF. Very important for the health of your ignition system. Good Luck. |
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1- 1946 CJ2A
2- 1949 CJ3A |
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Spinnas
Member Joined: 24 Apr. 2018 Location: AZ Status: Offline Points: 375 |
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Along with everything already mentioned(ground, check sender for full movement, etc), there should be a screw accessible from the back of the gauge to calibrate its reading.
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athawk11
Member Joined: 18 Jan. 2012 Location: Arvada,Colorado Status: Offline Points: 4145 |
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Good point. Some reproduction gauges do have an adjustment screw on the back. Originals and some reproduction gauge do not an adjustment screw.
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1- 1946 CJ2A
2- 1949 CJ3A |
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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SInce the sender is a variable resistance device be careful to clean all the connections from the sender to the gauge. Corrosion, dirt, and paint can affect the gauge reading.
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'47 CJ2A -- #114542
Warn FF D41 rear Lock-Right locker 11" drum brakes Dual master cylinder T90C Transmission 16 X 6 Jeep truck wheels Cooper STT Pro tires |
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binthere
Member Joined: 29 Nov. 2010 Location: Cherryville B.C Status: Offline Points: 707 |
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It could also be that the float is partly filled with gas and only reads half full. The new gages in the tank have a plastic float and it soon fills with gas. This has been discussed before, and I believe there is a brass float from a mustang that is the same as the plastic one. Just replace the float! Ask me how I know!! LOL
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chuck
1953 CJ3B "a fistfull of dollars" 1949 willys jeepster "a few dollars more" and a few other retirement toys |
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Old Man Army
Member Joined: 29 Nov. 2017 Location: Lexington, SC Status: Offline Points: 6 |
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Gentlemen,
Thanks for all of the advice. I decided to start simple and pulled the old sending unit. I cleaned the top and found a bare spot on the body to check if the unit worked. It does! I ended up cleaning the rest of the top of the sending unit, re-installing it, and now have a working fuel gauge! No more wondering if I'm about to run out of fuel while driving.
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ndnchf
Member Sponsor Member x 2 Joined: 22 Sep. 2017 Location: Virginia Status: Offline Points: 2177 |
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Glad you got it fixed.
FYI - Walck's sells a sending unit with a brass float, around $35-40. I put one in over the winter and it works great.
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1948 CJ2A - It goes nowhere fast, but anywhere slow.
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