Bloody Electrical Bugs!!!!

A few things have been going on in my comanche. Some from when I bought it, some a little more recent. The easiest thing to do is list them seperatley i guess.

Gas guage has never been accurate. It constantly sweeps when I go down the road and the low fuel light comes on at about half a tank full. No idea why, it's been like that since i got it. Now I use the trip as the gas guage.

Cruise control has never worked. I don't know what circuit it runs on so i can't even check the fuses. Heard it could be the little yellow box under the dash or the contacts in the multi-switch.

Temp guage did work for a while, then after I changed out the thermostat, it started reading extremely high like it was overheating, but it wasn't. A week later, it just quit. No reading. I tested the temp sensor on the thermostat housing according both of my service manuals and determined it was faulty. New one. Nothin. Was told it could be the temp switch on the back of the head. Replaced it. Nothin. Now I just live with it.

Not much of a problem, but kinda annoying. My speedo sensor went out a while ago, and ever since i replaced it, it seems to be fast by about 2 mph. I know that when I got stopped for doin 70 in a 60 it was dead on. Now, when i pass all those radar things that tell you how fast you are going compared to the speed limit, it says i'm 2 mph slow. I though it could have been the radar devices but the same thing has happened at multiple locations in different counties. That and everybody seems to want to pass me when I'm doing the speed limit. Could this be a result of the sensor?

FYI: It's a 91' eliminator 4x4 automatic with a 4.0 HO. It does have 30x9.5 tires, so I don't know if it will make any difference. Any help would be great.

Anyone? At all?

There is not one answer for all your problems. The first thing I would want is the factory service manual. (or on cd). Not Chiltons or???????????? Your vehicle is 15 years old and that could be part of the problem. Your in Spokane? Humidity and corrosion? Here in Mi. its salt corrosion. I know everything should be in weather pack connectors but stuff still goes bad. People probe in to wires, splice stuff, etc. You could have bad grounds. Make sure all the grounds are good first. The serv man will give you a wiring schematic or diagram. This is the road map of your electrical system. By using electrical concepts and principals you would use the map to find the problem. For ex. Your temp sender. You need a good ground between the Battery and the body and the battery and the engine. Manuals will show locations. You would locate each wire in the circuit and test that wire. Your looking for resistance. You basically want to know that the wire is not corroded or the connectors on the ends are not bad. You need to prove or disprove each circuit. You need to check each sensor or switch, etc. as you go. I know it sounds like a real pain. It is. It is the way to fix stuff though. You cant throw parts at it, you will go broke. You need to pin point and verify each piece of the map, bit by bit. As you go through it concentrate on the circuit your on not the whole harness or it will be overwhelming. All push on connectors have to be clean and tight. Be sure the connector crimp to the wire area is good. You should use an ohm meter and have a feel of what your looking at when reading wire resistance. Buy some grease designed for electrical work and grease all the connections as you go along. Don't go overboard. You can cause a hydraulic effect if you put to much grease in some connectors and it will push the pins out of the connector. I work on stuff like this all day. Not much guessing. Trouble shooting.

ah yes, welcome to an Old MJ, I just finished rewiring my parking lamp circuit last night.

My thoughts.
The temp SENDER in the back of the head feeds the guage. Don't get a temp SWITCH, that's for the dummy light. Make sur eyou tell the parts man you have the guage, or he'll assume you've got a light.

Regarding the fuel guage.
A few possibilities.
Loose ground
Float is messed up
The sender is hosed.
From what you're saying, I'd look at the ground behind the drivers taillight, and inspect the wiring. Then pull the pump assembly out. The sender has two small copper fingers that move like a rheostat, it's likely that it's corroded or one of the fingers is broken, and it bounces around in there doing all sorts of funny electrcal things.

Youre speedo reads 2MPH slow? That's not really bad, and since you do have larger than stock tires I would expect it. The only fix would be a new speedo gear with a different tooth count, but then it would likely read 2 MPH fast, I don't think you'll find a gear that will compensate for only 2MPH.