Eagle

A '91 XJ cluster will certainly fit, physically, but you'll need to convert to an electronic speedometer, and the gas gauge will read in reverse because Chrysler changed the polarity.

Offset measurement from what to what?

Building a custom cluster will be a lot of work and a lot of expense when any cluster out of an '88 through '90 Cherokee will drop right in.

No. When I lost brakes in my '88, it was the height sensing valve itself that popped, so I still had the fronts. The fact we don't know of it happening doesn't in any way negate the reason the system was designed the way it was, and it doesn't provide me any rational reason for NOT ensuring that the system is properly bled.

This works fine -- for the normal braking fuction/circuit, which is what your foot feels when driving around. By skipping the FSM procedure for properly bleeding the MJ system, you have no way of knowing if there's air in the rear bypass line. If there is, instead of getting full braking to the rear if the front brakes fail, you'll get mushy rear brakes at best, or posibly nearly no rear brakes at all. The factory specified that procedure for a reason ...

Same here.

If I remember correctly, the 84-86 cluster gauges didn't return to zero when the engine is shut off, they stayed where they were. When the ignition was turned on later for a restart, they then moved to display the current reading -- which would be zero for oil pressure and cold (100) for temperature. I don't think you have a gauge problem, I think you have a no power to the cluster problem. Are you getting a reading from the volt meter?

Nobody asked about testing the gas and oil pressure gauges. I asked if they work. The engine must start and run, since your question about the tachometer mentions idle and then increasing the throttle. So when the engine is running, what does the gas gauge read, and what does the oil pressure gauge read?

This thread is about the temperature gauge, because that's what you asked about and that's what we have been discussiing. If you want to diagnose the tachometer, please start a new thread to discuss that. What's the status on the temperature gauge? Do the fuel gauge and the oil pressure gauge function?

Factory Jeep coils were all black. NAPA and Carquest "cargo coils" could provide 2-1/2" of lift. Numerous companies used to to sell 3" lift coils for the Cherokee -- it's not difficult to imagine that aftermarket coils might have settled a half inch.

The opposing coils don't have separate polarities. Both are 12-volt input. That would be one of the two terminals that also connects to other things on the circuit board. Then one of them connects directly to ground (the C-coil). The other connects to ground through the temperature sensor (the H-coil). So in your test setup, you need a 12-volt positive source to the terminal you determine to be the input. Then you connect the C-coil terminal directly to the negative terminal of your power supply, and you connect the H-coil to your potentiometer, and then connect the potentiometer to the negative terminal of your power supply. To run the test, you have to have both coils powered up at the same time, because the gauge operates by comparing the magnetic output of the two coils.

Does your potentiometer have the same resistance range that the temperature sensor operates in? The section Green Mesa provided from the 1986 electrical manual gives us some numbers: 55 ohms for 260 degrees, to 1265 ohms for 100 degrees (which is "cold"). So you need a pot that gives you approximately that range. I suppose they all start at zero, but if you use one that's rated for 10,000 or 50,000 ohms on the high end, it won't take much rotation to blow right past the range for the Jeep sensor. It does appear that your gauge is functioning. The second photo from Green Mesa is from the 1988 electrical manual, which is the one I have. The simple GO - NO GO test is to disconnect the wire from the sensor. This simulates infinite resistance and should peg the needle to Cold. Grounding the wire directly to the chassis (or engine) simulates low (zero) resistance, and the needle should peg to Hot. Your testing seems to have replicated that cycle, so the gauge itself is probably okay.

I guess we could say you're past the statute of limitations ...

Getting better. Put a real roof on it and I could start to think about maybe being interested.

You need the wiring diagram to determine which pole is 'C; and which is 'H.' Only one of them is connected to the temperature sensor. One gets a constant 12-volts, the other sees variable flow based on the resistance at the sender. The third pole at the gauge is ground, which apparently both circuits share. Since the back of the gauge has four, one of them is redundant and not used. However, we can make some guesses. Look at your fourth photo -- the one of the back side of the gauge. Of the three circuit traces that lead to the temperature gauge, the upper one also connects to a terminal on the other gauge on that side of the cluster. (Is that for the tachometer, or do you have the big fuel gauge there?) The middle one connects to two light sockets, plus the other gauge. So that one HAS to be either a common 12-volt feed, or a common ground. The trace from the lower contact from your gauge doesn't touch anything else -- it runs directly to the connector header. I'm going to guess that's the C-coil. If the lower one is the C-coil, the upper must be the H-coil, and the middle one is likely the ground.

You have 2-1/2" of lift in the front. As I mentioned, I'm less certain what the number should be for the rear. If stock is 21" then you have no lift in the rear, but if it's 20" then you have a 1-inch lift. And that's consistent with your first measurements. Measuring from the wheel center (axle centerline) to the flares means tire size doesn't matter. The attached photos are my '88 MJ at stock height. The tires are 215/75-15s and I don't have flares in these photos, but the wheels are the same as yours. You can visually extend body lines to get a sense of where they run relative to the top of the wheel rim (not tire). Based on my attempt at that, I'd say the numbers showing about a 2-1/2" lift in front and a 1" lift in the rear aren't too far off.

I agree 110%. Cutting into an OEM bed liner should be a hanging offense.

??? You can't "send" resistance. Resistance is a parameter of each part of a circuit. Wire has resistance. Each connector has resistance. A resistor has resistance (:duh:). A light bulb has resistance. An electric motor has resistance. You can measure resistance, with an ohmmeter, but you can't "send" resistance. You also can't send current. You can send voltage. Current is draw -- the amount of current used is a function of the device that uses the power -- you don't "send" current. Go back and re-read what Green Mesa posted.

In 2WD the front differential will be coasting, with the ring and pinion contact on the non-load side of the gear teeth. In terms of break-in for driving purposes, driving in 2WD won't be doing anything for you.

You don't use a feeler gauge to measure backlash, you use a dial indicator. And before you get to that stage, you need something to check the pinion depth if you're regearing. The factory service manual provides all you need to know for the job.

I think you measured incorrectly. If the tires in those photos are really 31s, that's a lot more than a 1-inch lift. In the front, at stock height 31s really fill the wheel opening, right up to the flares. Not as definitive as the method in the FSM, but since you still have factory flares and factory wheels, for verification you could do the approximate method of measuring. Measure from the center of the wheel center cap straight up to the bottom edge of the flare. For the front, stock height is 17-1/2". For the rear, we know that XJs (Cherokees) are 17". I don't think we have a definite, confirmed number yet for the MJ, but it's probably around 20" to 21"/

You do realize that the normal operating temperature is around 210 degrees (F), right? And the temperature at which water boils at sea level is 212 degrees. All internal combustion engines are too hot to touch at normal operating temperature. You can't go by touch, that's why we have temperature gauges.

Yes.

I'm not familiar with that piece of crap carburetor, but I've never heard of a carburetor with a return line. Remember, it was designed to operate off a mechanical fuel pump, and a mechanical fuel pump doesn't shut down if the pressure exceeds 7 psi. You are using an aftermarket fuel pump, so you need to take a look at how you wired it, and how the manufacturer says it works. My expectation is that it's supposed to run all the time. Fuel flow into the carburetor is controlled by the float and the needle valve. But ... you originally posted that if you keep working the throttle, the engine stays running. Is that correct? If that's true - then you obviously don't have a fuel delivery problem.

Carburetors 101: The carburetor doesn't take gas directly from the fuel pump into the intake manifold. The fuel pump pushes the fuel at around 5 to 7 psi. From the inlet line the fuel goes to a reservoir in the carb body called the float bowl. There's a float in there, that activates a needle valve. When the fuel rises to the upper limit, the needle valve closes and shuts off the flow of gas into the carb. From the carb to the engine, the venturi (or venturis, if it's a 2-barrel or 4-barrel) such the fuel out of the float bowl. Gas in the float bowl is only under atmospheric pressure, it's not being pushed by the fuel pump, as it is in a fuel injection system. The faster air flows throiugh the throat and past the venturi, the more fuel gets sucked out of the float bowl. When you step on the throttle, the throttle plate opens wider, which actually causes the velocity nof the air through the carb throat to slow down -- which, in turn, reduces the suction effect on the venturi and starves the engine of fuel. So there is also a plunger deally called the accelerator pump, which gives a squirt of gas into the throttle bore when you step on the gas to copensate for the momentary leaning out when the throttle plate first opens. If you can keep it running by working the throttle, you're getting enough gas. You have a problem with the idle circuit -- either that idle mix screw isn't adjusted correctly, or the idle air circuit is dirty and clogged.