gas gauge

[bdjr]

help :headpop:

need some info the the gas gauge. after i removed the tank and bed the gas gauge reads about an inch past full. always!. thought maybe i buggered the sending unit so i replaced it(thanks alex). and it still sits an inch past full! opened up the dash and pushed it over to empty and turn on the ignition and guess where it went(an inch past full). removed the gauge and metered it there are three prongs one at 12o'clock one at 9 and one at 6 as you look at them. there is 12volts dc between the 12o'clock and 9o'clock prongs but nothing between 9 and 6. i'm thinking either a solid short or solid ground. but not sure. what should i do next? is there a relay?

 

bill

[GirsMJ86]

no problem on the sending unit. sorry to hear it didnt fix your problem. hope someone can figure this out for ya.

 

Alex

[bdjr]

thanks alex, makes me think that there wasn't anything wrong with the original till i got a hold of it and broke the tab :oops: .

[GirsMJ86]

thanks alex, makes me think that there wasn't anything wrong with the original till i got a hold of it and broke the tab :oops: .

 

eh it happens. i have done that many times thinking something in one of my rebuilds needed fixed and turns out i just break it and the fix was something easy. i am in the process of painting and refinishing the tailgate. thanks again for that.

 

Alex

[88Manche]

I have the same problem, I had to replace my gas tank and while I was messing around in the dash i broke the gas gauge so when i put a new one in it doesnt register right even with the original sending unit?

[Mathis]

I just got my MJ out of Jeep dealer for same problem - full tank of gas always reads just pass half full - dealer says problem isnt the gauge but float and isnt made anymore. Hope this helps.

[DirtyComanche]

Check the resistance on the sending unit, if it checks out (0-90~ Ohms, IIRC), then the gauge is fubar.

 

 

Personally I don't care if the gauge doesn't work. I clock my tanks with the trip-ometer or go by the feel of things.

[Druville]

are all the other gauges fine, i know mine was being funky once b.c the gauge fuse was a little dirty, i replaced it and it helped. but my volt and temp gauges were also reading off.

[500 MJ]

When I took the bed off of my MJ, I didnt have a fuel pump becuse it needed to be grounded to the rear harness... maybe this helps?

[bdjr]

wow thanks for posting i thought i was being ignored ;) here is where i am at so far. the float and send unit is fine i disco'd them to check them out and pulled out seats to see if any damage was done when i put in the bucket seats. even disco'd the gauge reads the same almost an inch past full. after researching how the system works the tan wire that feeds to the gauge's bi-metal spring is not telling the gauge that there is less fuel. either the wire is broke or when i took the tank out it waved to a point that FUBARED the gauge. what a pain in the @$$. looks like i will be paying a visit to alex's barn 8)

[Eagle]

It would help to know what year MJ, because Chrysler reversed the polarity AND changed the ohm rating on the sender in 1991. However, there is a basic test you can use w/o knowing the year or polarity.

 

Step 1 -- disconnect the plug under the bed that's about a foot from the tank. This creates an open circuit. Turn on the ignition. The needle will peg to one side or the other (Full or Empty). Which side depends on the year. Don't worry about it, just note which way it went.

 

Step 2 -- go back to the connector you unplugged. It has three wires. Color may change by year, but ground is always black, and the fat, heavy wire is always the one that powers the fuel pump. The third wire is for the sender. On the chassis side, jumper the gauge power wire to the ground wire. Now go turn on the ignition and look at the gauge -- it should be pegged to the opposite side from where it was with an open circuit. If not, either the gauge is bad or you have a broken wire between the gauge and that connector.