Has anybody ever seen this before? I've been diagnosing a no-run condition. Wasn't getting spark, replaced distributor, now getting spark, but still wouldn't fire. Thinking I'd miss-indexed the dist, I pulled #1 plug to find TDC, bumped the engine, and she fired up and ran. Put the plug back in, no-start. Take the plug out, runs. While running with plug pulled, pressing a compression gauge into the cylinder is enough to smother out the engine. What on EARTH could cause this?? (Does not sound like broken parts rattling around in the valve train, but haven't ruled that out. Also intend on testing to see if the same thing happens when I pull different plugs, to identify if this is just the #1, or any cylinder).

Anybody ever see this before?

 

Check with all the plugs give us an update, if its just the one cylinder make sure the valves open and close, check compression go from there. Report back often until you fix it then report with updates if it comes back. The more info the better. Year make model miles?

 

Will do, partsguy. It's a 1995, 190k miles. Was getting 60+ psi in the cyl #1. Going to try pulling other plugs tonight and see what happens, and take the valve cover up and check into the valvetrain-- but logically can't come up with a scenario where this could happen...but seeing is believing. Any help, much appreciated!

 

60 psi is too low Wingnut. The range should be 120 to 150 psi.

Did you get the plug wires hooked back up in the firing order - 153624? #1 plug at about the 5:00 o'clock position on the distributor cap.

 

#1 exhaust valve not opening due to rocker/pushrod problem?

Thinking it's blowing back into the other cylinders.

Backfires when it does run?

 

Firing order issue... maybe.

180 degrees out? Guessing here.

 

Wrong firing order won't cause the gauge to snuff it out.

180 out it won't run at all.

 

Answer?

 

Post #5

 

will recheck plug wires... agree 60 psi is low, but it's a compression gauge with a rubber boot fitting, so likely attributed to poor seal when I'm pushing it in there. Didn't backfire when running -- loud as hell without the plug in there, but not so loud I wouldn't hear a backfire, I don't think.... will update after I get to the garage tonight...

 

does it run with just the plug wire removed and spark plug screwed in ?

 

Nope, only runs with plug removed -- plug wire being attached or detached does not seem to affect it... heading to the garage now... stay tuned for more info...

 

Waiting patiently lol

 

Well, I think I've stumbled upon an answer, albeit in a roundabout way. I started to make a video to post to prove I wasn't crazy. By pure coincidence, every time I attempted to start the jeep with the #1 plug installed, I was inside the vehicle, using the ignition. Each time I started it with the plug out, I started it using jumper wires on the solenoid. As I went to start it this time, I put all plugs in, and used the jumper wires. Started and ran beautifully. ITS THE IGNITION SWITCH. I suspect that if anyone else tries it, their jeep too will run with a plug pulled, and with a little dumb luck, could also smother the engine by pressing a compression gauge in at just the wrong time. I've done it 10 times now, and each time it starts and runs with the jumper wires, but will not start and run by putting the key into the start position. Cranks, but does not fire. Can't explain why, perhaps that's just how ignition switches fail?? Either way, I'm going to get a beer. Thoughts? And many thanks to those who've taken the time to help.

 

Hi, was there any long term fix? I bought a '98 Cherokee, in New Zealand, had been dead for a year, 'no sparks'. After fooling around a few weeks cleaning grounds and connections I pulled one HT lead off, stuck a spare plug in it laid on the rocker cover. Stand by jeep so I can see engine, reach in window, Turn key to check for sparks, yep, and the thing starts. airbag light stays on.

A week later, a few more dielectric greased connections/grounds, HT lead off, it starts fine. HT lead back onto plug, starts and runs and I drove it 20 minutes. No CEL, all normal, all gauges, everything. airbag light not on.
Park again, turn off, turn on, runs 2 seconds.....which leads me to ignition switch or it's kissing cousin the SKIS module.
I have not yet tried a ODB2 reader to see what that says.

Sounds like jumper wires bypass the SKIM ? and my HT disconnect maybe confuses it to let it start once.... maybe this is a Dead Jeep recovery thing?

Dave in Noo Zealand
'95 Cherokee and nearly a '98 Sport