d00med

Speculating that's my problem as I don't have time and would love if just replacing it fixes this intermittent issue of not starting, or starting, or sometimes aaaalmost starting for an instant and then nothing more. Will probably get one as a shotgun repair approach. Thanks.

Rogue4x4

Well...you need to put the time into proper diagnosis to be sure. Hard starting, intermittent starting or whatever it is you have can be caused by many things. Speculation won't tell you what is wrong with your ride. Proper diagnosis will. But it's your ride...throw money at unnecessary parts if you want to. You've given a pretty vague description. More details if you want better guidance.

d00med

I agree it's not a smart method. But it runs great, no symptoms except this recent one of usually starting as normal and occasionally (more often recently) just cranking away without ignition. The coil wire seems to have clean connections and I'm not sure of many other single failure points that might just age out in this manner. I guess I'm trying the magical approach to save time over money. I'll try a fresh wire first, they fail too.

Rogue4x4

Well, you need fuel, spark and air for the engine to fire and run. Have you verified proper spark, plug gap, continuity checked the wires? Cap and rotor ok? Verified fuel pressure? These are some of the things you need to be doing to track it down. Don't just throw parts at it and hope for the best. You may mask the original problem only to have it return later. If you don't have time then take it to a mechanic. Probably will cost about the same as just throwing random parts at it.

Stabsthedrama

I don't think I've ever even heard of one of these coils going bad. Try doing cruiser's coil refresh tip (squeezing the receiving prongs closer together and spraying the area out with contact cleaner), but otherwise I really doubt the ICM is your problem...

d00med

Granted I'm making assumptions based on performance when it does start and tune up not long ago. Mechanics not usually an option given they only work weekdays. But no, though the wires are less than a year old I have not checked them.

d00med

That's interesting input about the coil. Even after 25 years? What do you mean by receiving prongs?

('89 4L 6)

CCKen

I had a coil go South on me once. The motor would bog down when doing a fast acceleration from a stop. It would start & idle fine, just gave up the ghost when putting a load on the engine.

I don't know if the '89 coil has the same specs as a Huge Output 4.0, but you can open this link and scroll down to post 59. It shows how to test a coil.
https://www.cherokeeforum.com/f2/gre...e-6558/index4/

Stabsthedrama

Do what Ken suggested and test it, what I meant was bending the prongs back in (truck side) not the posts coming off the coil itself. You first spray the area out with contact cleaner after removing the coil, and then use a pair of plyers to squeeze in the 2 prongs (that the 2 coil posts sit in) together a bit more. Should be done at least once in the lifetime of a vehicle, so if your coil is indeed OK, it should definitely be done anyway.

d00med

You all were of course right not to just jump on a new ignition coil, and the old one passes the DC resistance test just fine. A closer look and I would have seen that one of the connectors going into the block (ICM / Ignition Control Module) that the coil rests in has broken, leaving a hunk of plastic inside the connector and signs of corrosion on the pin and socket (this signal is GND). I can't seem to pry that hunk of plastic out and if I really am unable to, may just go get a replacement block from the wrecking yard and a new pigtail I can splice in (with solder and heatshrink), for about the same price as that coil. I'm not at all sure what diagnostics would have led me to that, nor of course do I know yet if that's really the problem, but the intermittent nature of the symptom should have had me looking at connections and not the coil itself. A large inductor is not going to fail intermittently but instead just fail open or short, and that rarely, as stated above. Thanks for the help and feedback.

CCKen

"Solder and heatshrink". I like that... Good choice. Sounds like you have your thinking cap on.

DFlintstone

Ken, I stole that coil test and added it to the info in my signature. Cool, Thanks!

CCKen

That's what it's there for bud.

Keep in mind that the wiring diagram is for a '97 - '99 XJ. Maybe '96 (?)

DFlintstone

10-4, I caught that. I just now finally found, (after looking a bunch of times over years), values in the 84-98 Chiltons for a 4.0.

Primary, Diamond, .97-1.8. Toyodenso, .95-1.2 (ohms)

Secondary, (to primary pos), Diamond, 11,300-15,300, Toyodenso, 11,300-13,300 (ohms)

So I guess I'll change that! "ASD? We don't need no stinkn' ASD's

Edit. I did actually find identical, matching info in a FSM for 96.

cruiser54

See Tip #3 in my pink link below.