Eagle

I would look for a wiring harness from an '89 or '90 Cherokee. Yes, the tail light and brake light wiring is different in the MJ, but with the electrical manual that's an easy adaptation.

Sorry, I don't know. I'm pretty certain I stumbled across it once, many years ago, but I certainly don't remember page numbers.

ECU?

I never knew there were more than one.

You are not having similar issues. The turn indicator is not in any way related to the brake system warning light. The usual cause of flakey turn indicators on the dashboard is the front turn signal sockets losing their ground, and trying to find a ground path by back-feeding through the indicator light on the cluster. Check your front turn sockets and the grounds for the front lights in general. Going forward, it's better to start your own threads rather than hijack someone else's thread on a different topic. That just creates confusion.

No, it's not. If the brakes were worked on recently, whoever did the work could have tripped the shuttle valve in the distribution block while bleeding, and not known enough to re-set it.

UP? Do they use salt on the roads up there? If so, check ALL the brake lines (or have them checked by a mechanic, on a lift) very carefully. MJs do not like road salt, and the brake lines often fail as they age. A frequent point of failure is where the rear brake lines (there are two) pass over the gas tank. If the brake lines look good -- have a shop or a trusted mechanic bleed the brakes to get the old fluid flushed out. Brake fluid is hygroscopic -- it attracts water vapor, which condenses in the brake lines and collects at low points, allowing the lines to rust from the inside out. I prefer to use silicone brake fluid. It's much more expensive than conventional brake fluid, but it's NOT hygroscopic, so it doesn't have the problem of getting moisture (and water) in the lines.

As Eaglescout526 posted, have to tried rotating the headlight knob? The dash lights are on a rheostat -- they can be dimmed all the way to full OFF by turning the knob.

Welcome to the inner sanctum. When your grandson gets the truck, I hope he will join us, and learn to appreciate the Comanche as a unique and rare vehicle as well as a significant memento of his grandfather. The factory recommendation was 10W30 or 10W40. I run Castrol Syntec 10W40 and change the oil and filter at 5,000 miles. My 1988 Cherokee has survived to 287,000 miles on that, so I see no reason to change. If you are in a VERY cold climate (such as northern New England or Montana/North Dakota), you might consider 5W30 or 5W40 for the winter months, just to get easier starting and faster oiling when cold. Definitely drain or siphon the old gas out and fill it with fresh fuel. No need for high test -- standard grade is all that's required. The '87 has a knock sensor, so it will control the timing to avoid engine knock/ping.

But the Ford axles are narrower than the stock MJ axle.

Axles are the same but you will need to flip the spring perches.

Definitely. You have the central axle disconnect on the front axle. That's operated by vacuum. There's a multi-tube vacuum harness that operates that, and it happens to be located right under the oil filter. Over time, drips from oil filter changes soften and destroy the connectors, resulting in vacuum leaks.

Fusible links are fuses. I would not try to repair them. Downoad the electrical manual, find out what their rating is, and replace them with new wire and actual fuses.

Check the wires the run along the frame in that area. Look for abraded insulation or broken wires.

On an '89 MJ the fuel filter is mounted to the frame rail, beneath the vehicle on the driver's side. If that's not where you saw smoke, what you saw wasn't the fuel filter.

You have it backwards. The "On" position is the 'Run" position -- power to the fuel pump goes through the ballast resistor. The resistor is bypassed when the key is turned to the "Start" position.

Much better, but punctuation includes a space between sentences. Shorter paragraphs would help, too. If the starter and solenoid work out of the vehicle, the only thing you can do is check all connections.

You have a switch for the aux fan but have you verified that the aux fan actually works? The one in my late-wife's 2000 XJ locked up for unknown reasons, and blew the fuse. Without the aux fan, the engine would get up to the red zone in light traffic on warm days. A new fan (and a new fuse) fixed it right up.

Definitely sounds like U-joints. Clunks could also be control arms, but that wouldn't cause tight steering.

Correction -- AIR flow isn't restricted. The tubes are probably clogged with sediment, and corroding from the inside.

Your hi-flow water pump may be pushing the water through the radiator faster than it can shed the heat.

If you still have the original radiator, you're due for a replacement.

You tried both American and metric Allen wrenches?

Read the thread you just posted in. The problem isn't the gasket on the oil fill cap, the problem is engine blow-by and a PCV that isn't sucking the blowby out of the crankcase.