Eagle

I have them on my '88 XJ and I'll be converting at least one of the MJs to them in the near future.

You didn't believe me when I wrote that my info came from the FSM? ETA: I don't understand why the first page is upside down. It's oriented correctly when I view it in Photobucket.

No.

You have a real mystery. The voltage should change more than 0.1 volts through the range of speed settings. Does all wiring appear to be factory?

Studs are just as accurate as dowels. The interface of the head to the block, horizontally, is not critical to the thousandth of an inch. You just want to cylinders to line up under the valves and the water and oil passages to line up well enough to allow passage of coolant and oil. Also, pay attention to torque. The bolt with the pipe sealant gets a lower torque than the others. Also, be aware that the torque values for the 1984 thru 1987 engines were different from 1988 and newer.

I took the liberty of editing out the color background codes. Dunno what you did, but ... DON'T DO IT AGAIN!

The arm should be horizontal with no load in the bed.

One or two of the head bolts penetrate into the water jacket and have to be sealed. You wrote that you used RTV on the bolt that needs it, but I wonder if RTV is the correct sealer. According to my FSM for the I-4 engine, the head bolt at the left front position (#8 in the FSM illustration) should be sealed with "Loctite Pipe Sealant with Teflon 592 or equivalent." RTV is a gasket sealer, not a thread sealer. Back in the halcyon days of my youth, we used a sticky black Permatex product for the head bolts that penetrated the water jacket, but I don't remember the exact name for the product. Also, the head gasket can only go on one way. Be sure the side marked "TOP" is facing up.

While you are repairing the brakes, I would strongly advise that you either repair the rear height-sensing valve or bypass it completely.

If it doesn't turn over, you should be looking at a weak battery, bad starter, bad starter solenoid, or bad starter relay.

Why don't you first verify that the problem is with the ground, by hot wiring the blower motors and seeing if they run?

I wheeled my '88 MJ for several years with a 4" lift and 31s and I never touched the u-bolts on any obstacle. If that's a major concern, it should be easy to fab a couple of u-bolt skid plates.

If you have voltage to the fan connector with the switch in all positions, the problem isn't the resistor pack. Even when the resistor pack blows its internal fuse, the fan will run on high. Have you tested the fans (old and new) by hot wiring them directly to the battery? Do they run? If they run, and you have voltage to the connector, then the only thing left is the ground connection.

Sockets and grounds.

Why did you "have to" use 5,500 RPM? I know the factory tachometer sets that as the redline, but the 4.0L engine (especially the Renix version) doesn't make any more power above about 4,000 RPM. It's a torque engine, not a race engine. There is nothing to be gained by running any higher than 4,000 to 4,500 RPM. I told you to use 5,000 just to leave some "headroom." Between an '88 XJ, an '87 MJ, and two '88 MJs I don't think I've ever seen the north side of 3,500 RPM in well over 300,000 miles of driving. (The '88 XJ alone has 287,000 on it.) The original 1987 model was rated at 173 horsepower at 4,750 RPM and 220 foot-pounds of torque at 2,000 RPM. The horsepower rating for this version was raised to 177 horsepower at 4,750 RPM and 224 foot-pounds of torque at 2,400 RPM for model years 1988 through 1990. You gain absolutely nothing by revving the engine beyond the horsepower peak, and you get the best driveability by staying closer to the torque peak -- which is 2,200 to 2,400 RPM.

4 liters is 244 cubic inches. Plug that into the formula, use 5,000 as the peak RPM, and do the math. But WHY would you use a carburetor on a 4.0L when the EFI is so much better? we don't know if the computer for the 4,0 works, just a back up option if it don't, Redwolf That's an expensive backup. You'll need a new fuel pump, because carburetors only want about 5 to 7 psi, not 40. You'll need a new distributor, because the one in the 4.0L Jeeps is controlled by the ECU. You'll probably need a new coil to go with the new distributor. And you'll need an intake manifold on which to mount the (expensive) new carburetor. I'd say you're looking at between $500 and $750, minimum, all to avoid buying a used or reconditioned ECU for a Renix 4.0L that you can probably find for $25. Doesn't sound like a great plan to me.

You are over-thinking, and worrying about things that don't need to be worried about. The u-bolts are 14mm diameter. Even at the weakest grade for carbon steel, the tensile strength is 58,000 psi. Each u-bolt will support 13,837 pounds in tension -- and there are four u-bolts per vehicle. That's 55,348 pounds. The load on the rear springs of a fully-loaded metric ton Comanche is how much? 2,800 pounds? 3,000 pounds at most. That's a safety factor of 18.45:1. The greatest safety factor I can recall hearing about in structural engineering class was 6:1. How many MJs have you ever seen with the axle fallen out because the u-bolts broke?

Shackle bolts are 14mm, but if you clean out the inside of the bushing sleeve really well and coat the bolt with anti-seize, you can use 9/16" grade 8 bolts. I know it works because I did it to get a friend's Cherokee back on the road. He had been swapping springs around, and he LOST the bolts. :doh:

4 liters is 244 cubic inches. Plug that into the formula, use 5,000 as the peak RPM, and do the math. But WHY would you use a carburetor on a 4.0L when the EFI is so much better?

Return the JKS shackles, buy a small manual wire brush and a small, cup-style power wire brush. Brush 'em up in place, apply two coats of Rustoleum, then let the shop do their thing. When you get it back, touch up any nicks they put in the paint and add a third coat.

I almost posted that^^ word for word!! LOL. You probably remember, too. When I bought my '88 XJ new, the service manager at the stealership was a racing buddy, and I hung out in the shop fairly often. Back then there were still a lot of 84, 85 and 86 Cherokees on the road, and every time I went to the dealer's shop there would be another one with a connecting rod blown through the side of the block. You DON'T beat on the 2.8L engine. (And what many people consider to be normal driving, unfortunately, is "beating on it" for the 2.8.)

What were you expecting for $500?

5,000 RPM. And you probably will never actually take it that high. If you do, you'll only do it once and after the engine blows up a carburetor will be the least of your worries. Why do you think we used 5,500 and 5,000 RPM in the examples? You need a 300 CFM carburetor. That Weber kit in Cruiser's link looks like just what you need.

See posts number 2 and 3.

Rust on the underside of the driver's side floor pan. Signs of leakage at the lower rear corner of the two wing vent windows. Signs of the heater core leaking. Check for small (or large!!!) cracks where the upper hinge of the driver's door is welded to the body pillar. Looks like it has a tilt wheel. Test the tilt mechanism -- they sometimes work loose.