YJ fuel gauge pegging full

hunterdan

hunterdan

Well-Known Member
Joined
Apr 13, 2009
Location
Morganton,NC
I just installed a new 20 gallon poly tank and new sending unit. It registers properly but if the fuel is rocked it will max out. If going down a smooth road it just moves around slightly like it always did. The original harness side had a 3 prong connector. The sending unit side had a 3 prong connector with only 2 wires because of no fuel pump. At the moment I have the tank on the ground wit elec. connected.
So far I have run a ground straight to battery
Looked like the float arm was kind of sloppy and I thought the connector that changes ohms was loosing contact so I bent it a little and still no go.

Any ideas appreciated.

87 wrangler/4.2 carburetor
 
Disconnect it, take it out of the tank and measure the resistance between the terminals with a multimeter as you move the arm position. It should be continuous, even though the resistance might not be directly linear with arm position (it may follow a curve, I don't know enough about Jeep units). It sounds like it might be a poorly designed/manufactured sending unit.
 
Maybe I'm completely missing the mark here, but is this a stock tank? Does it have any baffles in it? Could the gas just be moving the float that much when the gas is sloshing around?

Sent from my XT1254 using Tapatalk
 
let me make a short story long for those interested.
The original tank in an 87 can be the steel 15 or poly 15 or 20. It can also be an export tank made in Canada which is a 15 or 20 but different measurement from USA 15/20 tank.

There is only (1) US company who makes the poly tanks. Many distributors sell them under their own name. The one I got was on ebay from T-REX.

The funny thing is that my export tanks just different enough that you must buy their sending unit, fill and vent hose and tank skid guard. I am hard headed so I have modded the skid and made the hoses work.


Thanks, I'll check the resistance and as far as baffles, there are none. I also thought that maybe it just lets the float raise to full. I only have approx. 3 gallons in the tank now and I don't believe that's enough to slosh it to full on gauge. Wish I could think of a way to slow the float arm down as it is loose and will raise or drop easily.
 
Got it figured out today. I took the sending unit, plugged it in to the harness and raised/lowered the float by hand while looking through the rear window at the fuel gauge. As I raised it it would peg here and there. Also if I tapped the float arm to the side like sloshing fuel would it would also peg. I took the float arm off the rheostat and while doing so I noticed that the hole in the Teflon housing for the float rod was oversized and allowed to much play. I bent the wiper/brush arms further in and re-installed the float arm. That took out all the play in the rod. I just test drove it and not only does it not peg anymore when sloshing but the needle on the gauge is steady with no bouncing at all.
 
hunterdan said:
Got it figured out today. I took the sending unit, plugged it in to the harness and raised/lowered the float by hand while looking through the rear window at the fuel gauge. As I raised it it would peg here and there. Also if I tapped the float arm to the side like sloshing fuel would it would also peg. I took the float arm off the rheostat and while doing so I noticed that the hole in the Teflon housing for the float rod was oversized and allowed to much play. I bent the wiper/brush arms further in and re-installed the float arm. That took out all the play in the rod. I just test drove it and not only does it not peg anymore when sloshing but the needle on the gauge is steady with no bouncing at all.
Click to expand...

Nice. After doing a few fuel pump replacements on XJs I was going to comment that the resistance gage in the tank is increadibly sensitive and brittle. And side load would lose contact and the resistance would be nil prompting a full reading. Congrats!
 
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