I am working behind my dash this morning reconnecting gauges. I have replaced a couple of bad gauges (voltmeter, for one), and cleaned up a lot of wiring. None of these gauges besides speed and odometer have worked for a while. I now have all working gauges through testing with jumpers and test resistances. The dash panel is currenly on standoffs so I can work behind it easily, and the panel is connected to a dedicated ground (confirmed).
Prior to reconnecting the dash panel, I wanted to double check the ground to the tab at the base of the fuel sender. The tank is installed, but I can drop it about an inch without removing it. Now the question... I can feel (cannot see) the grounding tab. There is no ground wire attached. This would normally be a spade connector. On the other hand, I have confirmed that my tank is grounded by connecting a test light and checking the body of the tank as well as the skid.
If I have ground at the tank body, can I conclude that the sender is grounded? It will be a real pain to drop the fuel tank just to attach the spade lead to the sender tab. I thoroughly read the CJ gauge troubleshooting articles by John S, and of course he warns of checking and double checking the sender ground before buttoning everything up to prevent the sender element from pulling enough current to cause damage.
Can you get a meter probe to the tab to verify continuity to ground?
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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If the tank body is grounded, then yes, the sender is as well.
It's not the greatest ground, but it is there. My '75 didn't have a ground wire to the sending unit. It relied on the tank being attached to the frame for the ground from the factory. I know I swapped out the sending unit for one with the tab, but I'm pretty sure that a ground wire was never attached to it. That would have been around ten years ago.
Since you dropped the tank to feel around, I assumed it's still dropped that inch. I would try to attach a pre-wired female spade to it by feel. Then there will be no question it is a reliable ground, and run that wire to the battery securely along the frame.
@ renegade82 --> I can touch the empty spade connector with my fingertips, but that's it. Imagine reaching up from the bottom of the tank, pushing your elbow up close to the frame rail, and bending your wrist at the top of the tank... your finger tips can reach about 1" beyond the tab...also the tab is down below your fingertips in that slight well at the entry of the sender into the tank. Between the body underside and the top of the tank, there is just enough space for my hand. I cannot push a mating connector onto the sender tab...just not enough leverage.
@MikeRomain --> tried to get a jumper clipped on it to tie in a meter...no luck yet, but that was after fighting it for an hour. I'll try again when I'm fresher.
To the Forum --> Has anyone put an access panel through the floor of their tub above the fuel sender just for this reason? I was thinking something like an inexpensive kayak hatch that could provide about a 6" dia access when needed. Pictures?
Loosen the bolts at the back of the fuel tank skidplate and you would probably have the needed clearance. I swapped fuel lines on a CJ in a Moab campground this way a few years ago, not wanting to drop the entire tank.
Yep...I've done that. My problem is that it will only drop about 1" until the mounting bolt & washer for the skid strap hang on the lower lip of the rear crossmember. I will have to pull the rear crossmember to get any further this way. Not the worst thing to happen, I guess. I was up in there about two months ago to replace the crossmember due to rust. When I pull it this time, I'll notch the bottom lip to clear the strap bolt.
Lotta work for a ground. I think I'm in denial....
Personally I installed a ground on mine.. I used a small hose clamp and bared the wire, wrapped it around the clamp and attached it to the return line. I then took the other end to a good frame ground.
Im trying to trouble shoot why my gage is not working aswell, Just bite the bullet and drop the tank, with all the time you spent on trying to get around it you could have already dropped it and reinstalled it, Yea its a pain in the rear but what your doing sounds like one also, there's no pun intended, the trap door sounds like a good idea if your constantly having issues
I would not rely on the tank mounting as a ground for the Sending Unit. Don't forget, there is a gasket O-ring that seals the Sending Unit to the tank that is held in place with a locking ring. The O-ring itself is enough to insulate the Sending Unit from a good ground connection.
The ground terminal on the Sending Unit is there for a purpose, use it. A dedicated ground back to the battery is an even better idea that further insures the gauge functions as it should. After all, poor grounds are the #1 cause for malfunctioning gauges
In the light of a new day, I will be dropping the tank and connecting the proper ground lead. I will report back whether or not there is ground continuity to the tab. In any case, I run the dedicated ground. Thanks to all who have made suggestions on approaches to access this. Hopefully, by mid day today, I will have a complete set of working gauges for the first time in about two years. And also hopefully....two years from now they will still be working!
You may want to give some thought to soldering the connections at the sender and then making the connections so that you can attach/detach the sending unit while the tank is completely installed. (Basically making an extension cord for access) I did this when installing my new tank and now I can easily trouble shoot. Soldering the connections assures me they won't fall off.
I'd rather be lost on the trails than found at home!
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I was called away this afternoon. My next opportunity to finish this will be Saturday morning, weather permitting. I do all the work in my driveway...literally shadetree mechanic work. During the high heat of the day, the asphalt reflects enough heat to up the normal temperature by 10+ degrees. One of these days, I'll own some property with a garage... but for now, I need to push on.
All gauges are installed and wired. One quick disconnect connection supplies power to all. This remains unconnected until I get this sender grounding resolved. As usual, one small task requires tackling two or three larger tasks before the 'quick job' can be completed. Individually, I have tested the voltmeter (new), oil pressure, temperature, fuel gauge, and tach (replaced). A big part of this was simplifying the seemingly miles of unnecessary extra wiring under the dash. Much easier to follow down a specific connection now. KISS rules!
Hopefully, Saturday morning I can simplify the job of being able to drop the rear edge of the fuel tank by modifying the bottom lip of the rear cross member to allow the skid strap attachment to clear the cross member. Need to remove the frame mounted receiver hitch, the remove the rear crossmember, drop the rear edge of the tank.... and, simply connect the ground lead spade connector! As they say, installation is the reverse of removal...with one small intermediate task... Cut away a portion of the rear crossmember lower lip to allow the tank to be dropped (next time?) without all of the drama.
Stand by for the completion of this 'quick' wiring upgrade.