Eagle

This is the first time I have ever encountered a recommendation to wear ear plugs when welding. What's the reason for that? What kind of plugs -- are the cheap foam rubber ones I use under my shooting earmuffs adequate>

Chrysler used to sell a kit for converting the carburetted 4.2L Wranglers to electronic fuel injection. The kit was basically the complete engine room harness from a '94 Wrangler 4.0L. All the engine sensors are different, the ECU is different and mounts in a different location. I have not done the conversion, but basically you are scrapping everything that's associated with your engine and computer, and you're keeping the wiring that runs things like horn, headlights, brake & tail lights, and hazard flashers. The CPS for the HO operates on a different principle than the Renix, so in addition to replacing the wiring you will have to replace the CPS.

https://www.autozone.com/fuel-delivery/fuel-tank/spectra-premium-fuel-tank/163611_127816_0_7348_40163 14 x 18 is 252 miles. That should get you to a gas station. Even if you only use 14 gallons, that's still 196 miles. But 14 MPG is pretty awful for an MJ. Maybe it needs a new oxygen sensor? It should get closer to 20.

That's correct. AMC did the same thing with the XJ -- the early ones had either a 20-gallon tank or a 12-gallon tank. They were the same tank externally, the smaller one was just set up to accept less gas. They did it because the most base of the base models had such small tires that a full 20 gallons of gas put them over their rated load!

Take the bolt you have to Lowe's to match the thread. They probably won't have a grade 8 replacement (or whatever the metric equivalent is of grade 8), so you may have to go to Fastenall or on-line to find the right one. Use a helicoil to repair the stripped-out thread to the correct size.

It doesn't fit.

Try this: http://www.lunghd.com/Downloads_and_Links/CPS-87-90-update.pdf Note that this TSB is intended for use with a replacement harness that was available from the Jeep factory, so it has a rubber grommet that fits the 1/2-inch hole to seal it against water intrusion. If you're rolling your own harness, before you start drilling take a couple of minutes to figure out how you're going to seal a hole through the firewall (letting the outside inside), and size the hole accordingly.

You have a shortbed? The tank is 18 gallons. There was only one size tank for the shortbeds. Long bed could be 16 or 23.5 gallons. As others have commented, the tank from the longbeds is too long to fit into the shortbed chassis. What kind of range are you looking for? My '88 was good for 19 MPG in general, mixed driving. Figuring 16 gallons usable, that gives a range of 304 miles. I can't drive 300 miles in an MJ without stopping.

The actual response may be flaky, but look at the numbers. 9 + 5 = 14, 14 + 5 = 19. Equal sweep for equal numeric values. Linear. Then look at the temperature gauge. There's no way you can interpolate accurately on the temp gauge, but the oil pressure gauge is also calibrated on a linear scale.

"Car"? Go to your room -- no supper for you tonight!

I was describing what happens withOUT spacers, Don. Installing the wider KJ axle is a functional equivalent of your spacers. It moves the tires out from the bodywork, eliminating or alleviating the rubbing.

That's a feature if you plan to run large tires on Jeep rims. On stock Jeep 15x7 rims, 31x10.50s have the sidewalls come very close to the inner fender and the leaf spring. I routinely came home from Paragon (off-road park, now closed) with the insides of the rear wheelwells polished smooth and black from the tires rubbing. Never happened on pavement, but close enough to be a potential issue anytime the axle would deflect other than straight up and down. But you have to watch out if you run aftermarrket wheels with less backspacing than factory, or the tires will extend beyond the flares and you risk being ticketed.

I would use an MJ or XJ Dana 44 if I could find one for a reasonable price, mostly because that's the "right" (meaning correct) axle for the vehicle. Second choice would be the newer (97+) Chrysler 8.25" -- and I would seriously consider the disk brake version from the Kiddie Jeep.

Do you just want power windows and locks, or do you want a functional remote lock as well? The early remote system were infrared, not radio, and they sucked. If you just want to power the locks and windows, you don't need a dash harness, you just need a wiring diagram and a couple of spools of wire.

Too low. You need .5 to .8 volts. http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm (Scroll to the bottom) Note that the section on the TPS gives you the TSB for upgrading the CPS harness. That's a good idea in any case, but if you're that bad right off the CPS plug, improving the harness can't make .1 volts into .5 volts.

Agreed. The factory manual calls for the resistance (ohms) test, but the voltage test is what tells the tale. The fact that unplugging and reconnecting got a start, even momentary, strongly suggests that the CPS is your problem. Has your vehicle had the TSB modification to bypass the main harness and connect the CPS directly to the ECU? That eliminates a lot of wire and reduces voltage drop -- which a tiny voltage like that can ill afford.

I second that. It's a relief to find someone who doesn't think "restore" means "modify beyond recognition."

You're about 15 or 20 years too modern. OBD-2 systems have a second O2 sensor downstream of the catalytic converter, to monitor how well it's doing its job. The Renix system only has one O2 sensor, right off the manifold. All it monitors is the oxygen content as the exhaust leaves the engine -- it has no way of knowing whether or not there's a cat somewhere downstream. Its only purpose is to control the air-fuel mixture.

You're not in California. This is an '87 MJ? There is no "Check Engine" light. The only light is an "Emissions Maintenance" light, and that's only a mechanical timer that reminds you to change the oxygen sensor at 80,000 miles.

To clarify, the three wires are in the chassis harness, not pigtails from the WJ control panel? That diagram is from the 99 WJ manual. Have you looked at the corresponding diagram from the 93 XJ electrical manual? Something doesn't make sense. Your image is too small for me to read, and if I enlarge it the pixelation is still unreadable. But it looks like that connector has five wires, with letters. But your table of functions shows seven wires, and they aren't identified by letters. I can't do anything with what you've given us. If you have three wires left over, and there are only five wires, that means you have connected two wires to a panel with seven connections. What did you connect to what?

The voltage regulator is built into the alternator. Not the ECU, the alternator itself. Assuming your alternator is working, the first step is to see what you have. The numbers CS-121 and CS-130 refer to the case diameter in millimeters. 121 mm is 4-3/4 inches, 130 mm is 5-1/8 inches, so get out your tape measure. (Disconnect the negative cable from the battery before you go poking around the alternator with a steel tape.) Looking at Autozone's alternators on-line, they say their new-manufacture Durolast Gold alternators may be 121 or 130 mm in size, but all are rated at 100 amps. That doesn't make sense to me. There's an independent shop near me that just rebuilds starters and alternators. I just had him rebuild an alternator for my '87 MJ. I wanted to be sure it was a 100-amp, or upgrade it to 100-amp if it wasn't. Initially, he said "No problem." Once he got into it, he found that it was a CS-121 rather than a CS-130, and that he couldn't find a 100-amp winding for the smaller size. If your alternator is the CS-130, it's probably good for whatever you need, and you can wait until it fails before worrying about upgrading. If you have a CS-121, then you need to find out if it's the 61 or 74 amp version. I don't know how to do that in the vehicle without a specialized tester, so you might want to pull it and have it bench tested. The 74-amp version might be adequate for your increased needs -- the 61 amp might be marginal.

I wouldn't worry about it. Any stock automotive voltmeter is not a high-quality, precision instrument. If the system checks out, just get used to where the needle sits and pay attention if it ever points somewhere else. On your gauge, if we assume a liner sweep (which I think the voltmeter is, there's a 5-volt step from 9 to 14, and another 5 volts from 14 to 19. So the white tick between 9 and 14 is 11.5 volts. Midway between that tick and the 14 mark would be 12.75. Your needle reads only slightly below that in the engine off photo (12.94 volts at battery), which can likely be attributed to voltage drop through the wiring. Voltage with the engine running should be not less than 13.5 and not more than 15. You are reading 14.48 at the battery, which is within spec and shows that the alternator is working. The reading at your gauge is just a hair under 14, which again is probably due to voltage drop in the wiring. If you see the needle pointing at that tick between the 9 and the 14 marks when the engine is running, that's the time to sit up and pay attention.

Now that y'all know they exist, don't go rushing out to buy one unless you really need it. The purpose is to increase the rotational mass of the flywheel to aid in preventing the engine from stalling under extreme low RPM conditions. But ... there are always trade-offs. For those of you who want quick acceleration, it works against that, because it means the engine has to spin up a heavier flywheel before it has any extra power to send to the wheels. It also works against compression braking, because it tends to keep the engine spinning at whatever RPM it's at. (Which, of course, is the purpose.) If your truck is primarily used on the street or for occasional, light wheeling -- you probably don't need it, and probably wouldn't like it if you had it.

The Renix era MJs used Delco alternators with built-in voltage regulators. You can swap in a larger one with no rewiring needed, but increasing the wire size would be a wise precaution. Don't try to go too big, or you'll have problems fitting the alternator in the space available. The base alternator was a CS-121. The optional was a CS-130. Don't try to go larger than the CS-130 in physical size. The CS-121 could be 61 or 74 amps. The CS-130 could be 85, 100, or 105 amp.

^^^ This. The concept still makes some sense for the 2.5L, since that doesn't have a lot of low-speed torque. I had never heard of it for the 4.0L and I'm actually surprised that it even exists.