Jeep Driver

Stick a philips screwdriver in the plug boot, you'll see spark jump off the screwdriver when placed near a GOOD ground.
Don't trust the VC.

Have you got 12 volts to the coil?

97grand4.0

The VC is a fine ground. Only has what..12 bolts to the head in it, unless, they are isolated? Changed my gasket 2 weeks ago but can't remember.
Ace, I see many responses that you have not replied to. That being said, it sounds like no spark. Before I put a used ECM from the junkyard in, or bought a new one, I would first put the old CAM sensor in, unless you bought a Mopar sensor. I had 2 from AZ bad right from the box and yes will cause a no start but usually will set a code.
If it looks like the coil is getting +12 and the tps, iac, and cts are getting their +5 voltage sources, I would lean toward the ECM.

dcollins3208

Have you verified fuel pressure? If fuel is good to go... Spray some starting fluid in the air intake (after filter), report back if it starts

kengofff

Try a different ground, the valve cover has rubber under the mounting bolts and of course the gasket. I made up a jumper that has a clamp from a battery charger that fits on the spark plug good, and an other clamp on the other end that will go on any other grounding source

ace

Thanks guys. 97Grand, you're right that I haven't been good about replying to all of the threads here. I'm truly wading into uncharted waters here, and I'm not great with schematics!

Next question: The coil should only be getting 12V when the engine is cranked, correct? I tested it with a multimeter with the engine off and got nothing, so I just want to make sure that's what I should be seeing.

ace

Update:

Today's steps:
1. Cleaned a few ground contacts on the block and frame
2. Tested the ignition coil (it's good)
3. Checked the crankshaft position sensor (it's good)
4. Tested the PCM's hot leads (where the fuses are plugged in - they're all good)
5. Tested relays themselves (they're good)

6. Tested power supply TO the coil = this is a problem. I'm not getting power to the coil when the key is on. But upon visually inspecting the wires leading back to the fuse block (PCM), I can't see any melted/frayed/damaged wires.

Again, I have changed the coil, the crank sensor, and the camshaft position sensor (under the rotor).

So, next question: could it be a faulty ignition switch in the steering column? Is that in play at all? Thanks.

Jeep Driver

Yes, it could be a bad switch.

97grand4.0

Are you getting power to the other sensors like the coolant temp and map when the key is on? If no, then the key switch is in play, if yes, I would lean toward PCM failure.

dr.zoidberg

I had an issue with my cherokee a few years back...drove me batty. I dont have anything really to test sensors except an obd2 palm scanner and im terrible with wiring and electricity in general but back to the point. Is it showing a check engine light? If so...what codes are being thrown...id start there...long story short...i threw parts at my xj...and it kept throwing an asd shut down code...turns out one of the plugs for my fuel pump relay in the relay and fuse block under the hood broke loose and fell back under the panel. Its a free thing to check all four plug resepticals for each relay in the fuse block.

ace

It's not showing me a Check Engine light. I tested the relay receptacle you mentioned, and it seemed fine.

I'm now trying to ascertain whether a bad ignition switch could crank the engine but not give it spark. I don't know how to test the switch to see if it's bad.

Bustedback

Do not probe any sensors with a test light, that's a good way to fry the PCM.

ace

I've been using a multimeter. Is that also a no-no?

Bustedback

A multimeter is the correct tool to use.

jawalter

Have you checked ALL the fuses in the distribution bloc under the hood? Had a 20a fuse blow and give me the same symptoms...

ace

jawalter: Yes, I have checked all the fuses, inside and out.

97Grand: I checked for power to the other sensors with the key on, and had it.

I took off the plastic tube/covering from all wires leading to the coil, visually inspected them, and tested for current from the PCM to the coil. That checked out fine. I also took apart numerous plugs to check for corrosion. They all looked fine. My engine bay is surprisingly clean for a 96. But then again, I am not getting it off road much these days.

So, even though it feels like throwing in the towel, I bought a new PCM yesterday. A couple of you have suggested this. Plus the symptoms mirror another no-start issue I had years ago. I'm hoping this will fix it, and that we'll finally let this thread be cataloged as one more resource for XJ drivers everywhere!