Fuel Gauge languishing & other Gauges read zero = due to welding of new cat?

So - I just got a new cat installed to pass my emissions test and get my red baron (92 XJ with 98HO) back on the road. Now - I've been having some problems with my fuel gauge reading artificially LOW for some time... it was consistently reading about 1/8-1/4 tank lower than was actually in there (better than the reverse I figure!) but since getting my new cat welded on - suddenly the fuel gauge is not only reading much lower but being really inconsistent. And now so are my BATT and OIL PRESSURE gauges. My best theory on this is that the welding wasn't done properly (no battery disconnect?) and it's somehow messed up the gauges directly or messed up the ground reference for all gauges.

So the question is - what can be done to reset my systems ground for the vehicle (and gauges) - SHOULD that be the problem (or else - what CAN the problem BE?) - AND what about the fuel gauge? Could the 'offset' have been due to a similar problem or is it just the death of my sender unit (that's PART of the fuel pump from what i've read??)... thanks much.

oh - one more thing - as a random topic... since the new cat was put on - suddenly i'm lurching and hestitating when on the freeway and I try to give it gas wide open. I'm guessing it's due to the narrow (low flow) cat in the middle of my high flow exhaust system and borla headers etc (?) - or should I look elsewhere and it's a random phenomenon? (or maybe it's related to the gauge problem above??)

You need to get out an ohm meter and wiring layout for the grounds and test them. One or more maybe corroded. Start with the battery post. Also check the O2 sensor grounds!!!!

I'd crawl under there with a flashlight and check the rear O2 sensor wires really close. Possible they are laying on your new Cat or were fried during the welding. The clip that holds the rear O2 sensors wires out of the way is a pain and gets brittle with age.

No telling what a short in the O2 circuit is going to do, I do know a short in my CPS caused some gauge issues on my 95.

I've done a bunch of welding on my XJ's and never had any issues. I do always kind of hold my breath though and get nervous when I do weld.

Many times when I've had gauge issues it turned out to be the contact strip to the gauge cluster. I've dreaded having to swap out the fuel tank gauge sender and learned on my YJ's, to check the contact strip before I mess with the fuel tank sender (the hard way). Clean the contact strip with a clean pencil eraser and then wipe it down with a good electrical contact cleaner and see what happens. It is a pain to do, but easier than many other options and cheaper. There was a TSB on this contact strip, Jeep is aware of the oxidation problems there.

I was also thinking if they used an electric welder, the ground path may have gone through the O2 sensor wiring and fried it.

Greetings Mr. 8mud!!!!:cheers:

Ecomike said:

I was also thinking if they used an electric welder, the ground path may have gone through the O2 sensor wiring and fried it.

Greetings Mr. 8mud!!!!:cheers:

Click to expand...

Back at you, It's been awhile.

thanks for the suggestions... yeah i was only thinking along those lines because I had a rear body panel replaced several years back and (INEXPLICABLY!) half my fuses were fried afterwards... there are a lot of people out there with more amperes than brains it seems.

okay- well i had a little brief look-see and DID notice that the three wires coming out of the fuel pump had been coming out of their corrugated hose jacket (you know what i mean?) and the harness about six inches from the pump was at kind of an awkward angle - so I tried stuffing the wires back into the jacket and cleaning things up a little, geometrically speaking - got back in the cab and started up and ran it around the parking lot a little - it was only a few minutes - while I can't say it's fixed (since it was such a small demo) - but things look VERY VERY encouraging!! I've never seen the fuel gauge that steady- and oil pressure went straight to 40PSI and stayed there etc... so I guess I'll unplug the harness tomorrow and shoot some deoxit in there and try to set things up so that the jacket slit isn't pointing down and the wires will be more secure... hope that works...
:cheers: