Gauges not working after rebuild?
 

So I searched and didnt see or find anything I though could be the problem. I have a 93 jeep cherokee, 4.0 engine, 4x4.

Last week we finished up the rebuild on my engine. Put the motor back in hooked everything up started it up and the temp was at 210 on the gauge, the oil gauge was tacked out to the right at 80. checked it with another guage at the sending unit and it was at 20 for oil pressure. The next morning started it up and the temp was out of wack also now sits right in the middle of the red now. Checked it with a laser temp reader at the thermostat housing and it said 204 degrees.

So I went and bought a new temp. sending unit and a oil pressure sending unit thinking this would solve my problem... well it didnt. So now im stuck and dont know what to check. the oil pressure guage seems to be right now most of the time but at times I see it sit at 40 and when I hit the gas move up from there but it always goes back down twords 18-20ish area.

If you guys have any ideas on what I could do it would be much appreciated!

All the ground wires back in place?

Yes, check grounds.

Yup just double checked have everything grounded good. Its weird the guages act like they work just off like the temp gauge goes up in temp after start up but goes to the middle of the red. And the oil pressure is all around the place(in the right spot sometimes other times not)

Is your voltage correct? Not overly high or low?

Voltage is right below 14.

At 190 degrees that temp sender should measure between 850 and 950 ohms to ground.
Lower resistance means higher temp readings. What does yours measure at operating temp?

Okay so I dont know if I did the readings right but i drove around town temp was at 205 ish and then came home too the readings(ground on the main engine ground in the back and the positive side on the temp sending unit) and it read 2.8 ohms??

Well... that'll peg the gauge alright. Do you have the correct sender, ie: gauge, not idiot light?

What do you mean sender? If your talking about the temp sending unit its the one that screws into the back on the bolck with the plug in on top. or do you mean my tester. the tester is a fluke has all diffrent modes.

block to firewall ground hooked up ?

Yup

no pinched wires between bellhousing and motor, under wotor mounts,melted to exhaust gotta check every where.

nope none anywere checked a few diffrent times

is any other electrial going bonkers,try another battery.

Its only the temp gauge and the oil gauge jumps around, but thats only sometimes with the oil. I cleaned up the battery really good the other night? you think I need a new battery?

There is a choice of either 1 or 2 + #3:
1.) Sending unit for the dash indicator light.
2.) Sending unit for the dash gauge.
3.) Coolant temperature sensor for the PCM.

any thing electrial done while motor was out

original sensors were on motor at first start up?

Oh okay I have number 2 then
nope
Yes at the very first start up it read 210 on the guage, then the next morning when we started it up it was outta wack replaced temp sending unit and was still acting funny

correct sensor bought i assume gauge and light look alike check part number on line...

sensor on back of head or thermo housing

freegdr----the sensor is on the back of the head

just trying to help out GRANDLICH

Yes the sensor on the back of head, and its the same part.

they look just a like

yup

well still trying to figure this out. I went around and tested anything in the engine bay that is a ground to something. found 3 maybe this will help??


-battery to engine block: .2-.3 ohms


-negative battery terminal to wall(3 inches long): .4 omhs

-NOW THE temp. sending unit(back of block): .9-1.0

these were all taken after the engine had cooled down quite a bit. I was thinking maybe replacing all these ground wires could help, but i did take all them off and cleaned the endes of each wire up. somw looked like there had some corrosion going on inside the the wire??