brucecooner

At a cold start, the 4.0 (1988 Renix) will settle in at about 750 rpm, with an occasional dip to four or five hundred every couple of seconds. Here lately once it's warmed up, it will idle at about 1250 rpm. Turning on the AC drags it back down to about 1000 even, but it still wants to idle higher. It's very very consistent in this behavior, normal-ish idle when cold, high when warm. It had a few incidents in the past where I'd start it and it would immediately race to about 3000 and stay there. I replaced the IAC valve last year, but I have seen that race condition once since. So it got better at least. Because this new behavior only happens after warmup, and the race happened at startup, I don't think they're related. So is there a sensor or system that affects the idle speed upon reaching a certain temperature? It's so consistent (normal at startup, high at warmup) that I don't feel like it's a vacuum leak, but it could be an unexpected leak when some valve or something opens up to a passage missing a diaphragm or something like that. Could it be related to an emissions system maybe?

Those are long gone on mine. So if you remove the nuts the bolts drop down unless you devote one hand entirely to holding it up. If I were smart I'd just put a c-clip or something down there.

I did that trick of jamming cardboard tubes together, sitting them upright in the battery tray at the point where the posts would sit, closing the hood, and getting the clearance from the final length of the tubes. This gave me fairly precise clearances at the posts. Negative looks to be about 8 and a quarter inches. With the positive side about 10 and 3/4ths inches. I can't remember the height of a group 34, but I think it was like 7 and 7/8ths. So not quite an inch on the negative side, but plenty on the positive side, which is probably where it really counts. So I got the group 34 and as all the old timers around here have said, it sat in a stock '88 tray without needing any mods. The stock hold down system wasn't very pleased with my decision, the nuts on the threaded uprights aren't going on very far, and I think I backed them off out of fear the bar might warp the battery. And don't worry, I moved the loom around that coolant hose further down so it's fully between the hose and battery. I plan to get a boot to go over the positive terminal too. This hold down is sturdy, but I have to wonder if there's any options for this system. The uprights tend to fall down, and I'd prefer something that's a better fit to the battery. Our Mustang has a sturdy fabric strap that goes across the battery that is the easiest system I've ever used. Loosen one tall 10mm bolt that sticks up on one side and lift the strap. Easy to put back and nothing drops down into the dark voids of the engine bay. Anyway, the $65,000 question, the whole point of this thread, did this fix my problem? YES! It's started every time I've turned the key since dropping this one in. As can be expected, about a week after I replaced this battery, the one in the Mustang gave out, so it was good I got this guy back on the road when I did. So a big round THANK YOU to everybody who helped out here.

It looks like the stock battery group size is 58, but lots of guys prefer running a group 34. It is also apparently a bolt-in fit in earlier XJ/MJ's? The size charts I've seen indicate the 34 is about an inch taller though. I have the stock tray without any sort of spacer in the bottom that some have mentioned removing. I'd definitely spring for the 34 for the extra cranking amps, but I don't want to run the risk of shorting against the hood.

I'm pretty suspicious of the battery at this point. The coil checks out (see below). I'm still running the battery that was put on there when I bought it a couple of years ago. The date on it is 01/22, and 2.5 years in the Arizona heat has probably not been kind to it. Add in also that the Jeep sat around for a while back when I was sick and working my way through the eternal brake job, so the battery was probably draining off a good amount. THANK YOU for the helpful pictures, that made testing a breeze (coincidentally, I have the same multimeter). All my readings are about the same as yours. The two small round posts show 0.6 across, but I can wiggle the probes and get 0.7. Mine does show what looks like rust inside the galvanized(?) outer casing, and the water sealant near the top front has a couple of mild breakaways... But if the interior is wires encased in a big blob of plastic, I probably don't have to worry as much about the exposure. (I have cleaned the posts, that gray stuff is Oxgard) If these coils are known to last that long, I'll be keeping this one. I seriously doubt any new one is as well built as the original (even it it was made in France). In other news, I hooked the jump box to the battery a few days ago. It didn't start on the first crank, but it did on the second. And evening before last I test fired it and it started right up. So I'm less suspicious of the coil and more of the battery at this point. It's a Duralast Gold. I used to run Duralasts in my Ranger, but I never got much beyond 3 years with one. This one has been sitting in the Arizona heat for going on three years, and sat without being recharged for stretches of time while me and/or the Jeep was down for repairs. The battery posts show 13+ at key off and 14+ at idle, which seems normal but I don't think I can tell how much cranking oomph it has just based on that. I wouldn't trust the Autozone test either. A few months ago they told us the battery in our Honda was good, but the key off draw was within spec so we changed the battery anyway and that was indeed the problem. Can anyone recommend a battery that might stand up to the heat a little better? Are the AGM's better for a hot climate? Are the Optima's worth the premium? Or are they all a crap shoot these days? One other question, is that flat spade connector between the small posts supposed to connect to something? Mine reads the same as the pictures, but I can't tell that there is anything in the coil cradle for it to connect to.

I'm late to this thread but WOW, nice truck and that is an epic adventure. And you even turned it into a seagoing Comanche. I've never made plans to take mine outside of the county (not country, county) I live in (but Maricopa is a big county). Although apparently the truck has no plans to travel beyond the borders of my driveway so it and I are on the same page, I guess.

"Liquified". Absolutely. When I first opened mine there was brown gunk inside, I'm pretty sure it was whatever rubbery stuff was originally in there that had long since turned to liquid. The brown gunk was everywhere, I sprayed e cleaner in both sides for a while until it mostly quit coming out. Then when I cleaned it the second time a bunch more came out. I remember someone mentioning that but the fuel pressure gauge says I'm at 32psi at key on so I hadn't considered the fuel system any further. I'll definitely jump across it next time I'm out there. As I understand it I can just delete the ballast and live with the slightly louder fuel pump. Does deleting the ballast affect the lifespan of the pump? I'd assume not since I think the resistor wasn't even on earlier models. A new ignition coil is $60 bucks from Napa, I'm seriously considering it. It would be just firing the parts cannon for sure, but I'm wondering how old reliable that coil stamped "Renix" could be. Maybe same age as the truck and likely to fail at any time. Or it could last another 40 years, maybe? At any rate I need to figure out that "trigger a crank from under the hood" push button arrangement so I can put the multimeter on various things while it cranks. Mostly so I can check the CPS voltage. The CPS would would have been moved to the new bellhousing during the recent transmission swap, and maybe the move upset it. It's odd to me that CPS's fail. I thought it just held a magnet that generates the current sent to the ECU when the teeth on the flywheel pass by, and didn't contain any moving parts. How do they fail? Has nobody figured out how to restore them, or modify them to avoid whatever failure case makes the cheap units to go out so frequently?

I originally thought the C101 was the source of all my trouble, as I could jiggle it and then it would start. What was really happening was something else was failing intermittently and my jiggling wasn't actually affecting anything. But I did open up and clean the C101. Twice because I'm insane I guess. It was super nasty inside, and definitely needed a cleaning, but it's cleaned up and snug now. I plan to delete it when the weather cools off. I started at the air cleaner and have been going counter clockwise around the engine bay cleaning up the connectors I see. It's a clean truck, never got dirty, but it looks like none of the connectors have ever been unplugged and some of them are a bit crusty after nearly 40 years.

Man, I could NOT unplug the big gray connector behind the kick panel to check it out. But, nothing under there seems loose or disconnect-y. No luck yet figuring out my no start (got sick for a couple weeks), but I have been cleaning up various connectors under the hood, doesn't look like anything has ever been cleaned. I went to do the cruiser ignition coil tip.... https://cruiser54.com/?p=41 And found out my coil might be the original unit, and it looks a bit rough. Looks like it might have event gotten wet at some point. I cleaned up the contacts on it, but I have to wonder if should I just replace it based on visual inspection and apparent age. Also, the cradle the coil sits in on my '88 (ICU?) doesn't look quite like the one from cruiser's tip. Ugh, picture is backwards. Anyway, I have the little connectors for the two pins on the bottom of the coil, but I don't see the "pins" as indicated in the tip. Is there some contact surface here that I'm overlooking? Those little connectors I could see were really nasty so I cleaned them up and spritzed some electronics cleaner into both the plugs. I didn't bend them inward, need to go back in and do that. I'm moving towards the plugs from here. The contacts inside the distributor were completely oxidized so I cleaned all the surfaces in and on the dist. cap so everything was shiny, and the tip of the rotor inside. Of course, none of this fixed my no-start... But it was stuff that needed doing. I've checked the fuel rail pressure several times, it is pressurizing well enough. My next step is to put the spark light after the coil and see if that thing's putting out any juice. I doubt it will be that simple though.

Would have never guessed there's an MJ with a BMW engine in it. That took some serious skill but the result is cool, and it looks like it will go wherever you point it.

That's intriguing because I took my kick panel off a while back looking for rust in the floorboard (yep, need to do some scraping and sealing there) and I just left the kick panel off. So there's a good chance those connections have gotten brushed or knocked on. Are you referring to a specific fuel pump related connection down there or all of them?

I didn't mention in my post but I'm going around to various under-hood connections as I can. I've cleaned that ground by the dipstick last year, but will get it again as I get around under there. I've noticed a previous owner added an extra block-to-firewall ground strap, somebody knew about these types of things. That was after a few seconds. The injectors are a rebuilt set I put in a couple years ago (bought from someone cruiser recommended, not some random amz or ebay purchase), so I hope they're sealing well but I should check the KOEO instant pressure. The fuel pump might be old and tired, like a lot of other things on the truck. I've been meaning to add the FP ground mod, but it's been hot here lately, and laying on the pavement is like being on hot coals. Yeah I need to invest in a creeper, it would see a lot of use now that my son has an old F150. I've heard about the ballast resistor delete. I actually cleaned the connectors on mine the other day, but the best part is no part, one less thing to fail would be nice. Unfortunately I park it facing north in our driveway and the weather usually blows in from the west, meaning the driver's side hood bay and everything near that edge of the hood gets pretty wet. I obviously need to start backing it in the driveway so the rain blows in the other side for a change.

EDIT: If you got to this thread searching for why your Renix will crank but not start, or get no-starts at random, it might be the battery losing its juice. A new Group 34 battery (yes, it fits in an '88 tray) fixed my problem. --- I got a no start a few weeks ago, popped the hood and jiggled the C101 and it started right up. I wound up cleaning the connector (see elsewhere), but after a couple weeks got the no start again. Hmmm. Jiggled the connector, started. About a week later, no start again, and it did NOT seem to be the connector this time. No amount of futzing got it to start. Went out the other day to attempt to debug. Put the fuel pressure gauge on and turned key on, 32 psi. Put the spark plug light inline, had my son crank it so I could watch the light and lo and behold it was a bit of a rough start, but it did start. So now I'm thinking the connector was just a red herring (it did need cleaning though, it was a bit crusty). My suspicion is that it was just not starting randomly for some unrelated reason. Note, randomly. Whether it was starting or not probably had nothing to do with my jiggling and fiddling, and was related to some currently unknown condition. On one or two of these no start days, it cranked a few turns, then stopped cranking as I heard a thunk from below the floorboard, which made me think the starter was having a conniption, that may be unrelated though. Once it starts it purrs, maybe like a slightly asthmatic kitten, but there's no sign of trouble whatsoever. And it keeps running. Sunday I cleaned up some connections under the hood and since it started that day I took it out on a pleasure cruise, twenty or so miles, and it didn't miss a beat. The non-start seems to have gotten more prevalent since it began, so I may be looking at something that's on the way out. What kind of things would lead to a no-start, but NOT a no-run, condition? Is some sensor somewhere going out? Something in the ignition system unhappy (coil, etc.)?

"Glass Run Channels" Dang, I'd have never been able to pull those words out of the air to describe it. Many thanks! This is the link from that thread for the part (Summit Racing): https://www.summitracing.com/parts/PQP-GRB-6110-84 And I might as well get a set of those spiffy replacement taillights while I'm ordering...

The plastic trim at the front vertical edge of the driver's side window on my '88 is cracking and breaking. This is the rearward side of the bar that separates the quarter glass from the window (see picture). I've hunted and hunted online for it, but no phrase I use seems to get any hits. Is this a piece that is reproduced?

Recently brought my son's rebuilt 302 back from the speed shop (going back in his 95 F150). The Heartbreaker did squat a little, but drove like the lump wasn't even back there.

Dang, I'm really sorry to hear this. He was always around, and genuinely helpful to me (and many others). I can't imagine how many old Jeeps are still running today thanks to his generosity. RIP Cruiser, and thanks for the tips.

I hadn't really looked at it closely until I read your comment, but the cowl gasket is in good shape. I think the water is blowing in from the driver's side hood gap when the wind picks up out of the west. I park facing north and we get some pretty strong gusts with some of our storms. I don't have a windshield washer reservoir at that spot anymore, which would block some from blowing on my master cylinder, but I'd rather it stay reasonably dry under there. I took a picture that shows the cowl gasket in place, but a HUGE gap down the fender. I wonder if it's possible to modify a cowl gasket, or any piece of rubber I guess, to fit under that seam.

I had a few minutes of daylight and no other obligations today, and I couldn't leave cruiser in suspense, so I tackled cleaning the C101 today. The connector isn't as delicate as I had imagined it to be based on looking at it from the outside. But once I opened it up, ick-o-rama. The pins are pretty well gummed up with what looks like corrosion, but I didn't see any signs of the tar-crap, leading me to think this thing has been cleaned out before. Regardless, it needed cleaning so I went in with brake cleaner for a while, then switched to the electrical cleaner, going at it with a metal brush and an old toothbrush too. When I'd spray the cleaners down into the connector, some brown fluid would flow back out. It might have been rust or the old tar stuff's remains. I got as much brown fluid as I could out, but I feel like there's more left in there. I took q-tips moistened with electronics cleaner to everything metal I could reach until the q-tips quit coming back brown. I tried to tighten the female pins with a small hook, it looks like there's only one side, that mates to the bottoms of the male pins, but I could barely budge them. As a final step, I coated a q-tip with oxgard and hit all the male pins, not sure if it will help much but it might. It was a bit after dark when I got done, and it was still not what I'd call clean looking on the inside, but at least the metal parts looked sort of metallic again. There was a slick looking, greasy sort of resin coating on the inner plastic surfaces that I never got rid of. Again, maybe the remains of the original tar crap. I had been afraid this would be a bear to reconnect, but the bolt did the work of seating and firming up the connector. Once I bolted had it back together she started right up, so at least I didn't bungle the job. I was wondering if this would fix the wandering idle, but it was still there. No matter, it definitely needed doing. Big thanks to cruiser and the others for nudging me forward on this. But this leads me to my next concern. I park it in a driveway, and I'm pretty sure some of this corrosion is due to water making its way under the hood. I can see some water drop witness marks on dusty surfaces, and my uncoated brake master cylinder has rust spots all over it. (disappointed about that too, it's a Napa part, I didn't try to skimp on it) Also that deep well at the corner under the hood, where the firewall meets the inner fender, has a little bit of rust waaaay down there. I keep leaves and stuff out of there as much as I can, but I want to try and get a dremel wire cone down there and then treat and seal it somehow. This leads me to wonder if there's a gasket I could install around the edge of the hood or something like that to keep the wind from blowing so much water into the engine compartment. At the very least, I think I need some sort cover to keep water off the C101. Anyone have any experiencing keeping rainwater from gushing under the hood?

There's no slop at the pin, that bracket/pin went unused for a long time. I listened more closely today, and it makes two distinct noises. There's the general high pitched squeak, but as the bar works through the wheels there are two distinct pops, as if something is catching for a bit, and then jumping. May be associated with the fact there are two notches on the bar. I tried to grease the little wheels when I had it out, I'll just have pull the door panel off and hit it with some oil, see if that helps.

I think I had only ever considered C101 removal as the only option, and forgot about the cleaning tip. But it's been a busy week at work, trying to get a project sorted before a deadline, and then more plans this weekend. I've been bummed that I haven't had more time to fiddle with the Jeep.

I'm wondering if I did something wrong when I reassembled the check. I greased the little axles the wheels are supposed to roll on, but it still creaks and pops. And a properly functioning one should be quiet. I didn't grease the outside of the wheels, I assume they are supposed to roll along on the bar, otherwise you're scraping and wearing down the metal. I wonder if the spring is so strong there's too much compression between them and the bar, keeping the wheels from turning. But this is out of an old cherokee, presumably oem, so I'd think it should work.

The way mine creaks, I might be in the market for another one in the future, so good to know these are a viable option. Thanks for the update.

I wasn't aware cleaning it was an option. My approach to it has been "don't disturb it" though I'm sure it shakes around plenty while I drive. I have a can of the electronics cleaner stuff, I've hit some of the other stuff under the hood with it already. I might just unplug the 101 and blast the contacts, then hope I can get it plugged back in.

cluck cluck... I've done a few tips, but have been avoiding this one as "she runs okay-ish" and the thought of messing around with the vital and fragile C101 connector makes me nervous. Then I had a crank-no-start condition the other day. I had washed some bird crap off the hood (dang pigeons are a menace) and was going to drive it a few miles to dry everything off. But it would crank and crank without starting. It was dark out and I was wondering if despite my caution with the hose I had gotten something important under the hood wet, so I went inside figuring I'd let it dry and try again. The next day, same thing. It had come back from the transmission shop a week prior so my first thought was that someone had disturbed the CPS in some way. But upon raising the hood it was obvious the C101 was a little cocked out of place. I tweaked and snugged it up a bit and and she started right away. I guess it had wiggled out of place just enough... I was just lucky it did this in the driveway. Anyway, this is a clear message from the universe that it's time to bypass the crusty old C101. Too bad my soldering skills aren't the greatest. I know, practice... There's an excellent video featuring the famous cruiser54 on yt detailing this process, but I was wondering... Are there alternate connectors you can use that might idiot proof this process? Or is it just down to solder and oxgard and heat shrink tubing and patience?