Weird no-start

[HeavyMetal]

Its for my 97 XJ.

You start it fine, 1 crank, no problem. Itll run normally without any issue, drive, so on. If you turn it off, and try and start it again soon, it will crank endlessly, never firing. If you wait awhile, anywhere from 30 mins to a number of hours, it will fire right up again and run fine. Wash rinse repeat.

WTF is the possible cause of this? All sensors are new, distributor new, fuel pump new, coil new.

It doesnt matter how long you run it, i could start it, run it for 5 seconds, shut it off, same result.

[Burton58]

Isn't this the same symptoms as the last few years? Everything on there has been replaced. My only thought would be a screwy ecu

[HitItWithSomeSpeed]

^That or possibly NSS? The only other thing I can think of is a dirty contact in the ignition switch itself maybe? Or dirty MAP sensor? Id start with those.

[customcreationsllc]

I don't think the neutral safety switch would have anything to do with it since he said it cranks.
Same with ignition switch.
I don't think map would have anything to do with it since that is just mixture.

The first few seconds the engine runs in open loop (no sensors) usually until it gets up to temp etc, then runs off the sensors (closed loop).


First easy test would be does it have spark, Fuel signal, fuel pressure, etc.

My spitball guess would be Cam sensor. Engines will usually continue running if you loose cam sensor after it is running but not start, some times that is the same with crank sensors.
Try unpluging after it starts see what happens. Maybe it gets hot and stops working.



Second guess would be a temp sensor, maybe it goes haywire when it gets hot.
But that will usually run but just really hard to start. You can try unpluging it and it will go into limp mode.

Without plugging scanner in and, using a scope to read that actual sensor signal it is anybodies guess.

I think I still have all my spare XJ parts, computer sensors etc. if you wanted to plug an play.

[HeavyMetal]

Isn't this the same symptoms as the last few years? Everything on there has been replaced. My only thought would be a screwy ecu

its a little different i think...but this specifically started a couple weeks ago when i had a battery go bad. I put in a new battery and it started acting weird like this.

i just got it running by starting it with throttle, i let it run a little while, and now it starts every time i try it without any issue, runs smooth and clean, so on.

very odd. not sure if itll do it again

[customcreationsllc]

i just got it running by starting it with throttle, i let it run a little while, and now it starts every time i try it without any issue, runs smooth and clean, so on.

When you need to use the throttle to start it, sounds like a temp sensor.
It is like starting with the choke on when you don't need it or the choke off when you do.

unplug it and try it in limp mode the next time it happens.
The temp sensor that is on the thermostat housing.

Good luck.

[HeavyMetal]

When you need to use the throttle to start it, sounds like a temp sensor.
It is like starting with the choke on when you don't need it or the choke off when you do.

unplug it and try it in limp mode the next time it happens.
The temp sensor that is on the thermostat housing.

Good luck.

Good info, thanks Justin. Before all this happened, last weekend I blew up a radiator, and leading up to it, the Jeep was reading far below operating temp for a good 30 mins on the highway, before it finally went up to 210, and then blew the rad shortly after. I just replaced the t-stat and housing last night, the coolant temp sensor isnt a bad idea either.

[HitItWithSomeSpeed]

Obviously time to part out.

[Lycaon]

need a radiator?

[hippie metal]

Obviously time to part out.

Shotgun cage!

[Odinthor]

Obviously time to part out.

The only time I forsee Will parting out Heavy, is to put all the parts on Heavy 2.0 and/or DM 2.0

[CumminsJeep]

My XJ did this a few years ago and it had the same symptoms. The temp gauge got all screwy and started running like garbage on the way to work in the AM. Would crank and not start once I turned it off when it was hot. Once it cooled, it started. Also, when it was running shitty it would coincide with what the temp gauge was doing. If the temp gauge started bouncing it would run like shit. Obviously messing with the fuel trim. But when it went back to 195 it ran fine. I replaced the sensor with a NAPA one and I haven't had an issue since.

I would start there before replacing a computer.

[Chaos]

This is the same issue that's been going on in the white ZJ. At least I'm not going crazy.

[hippie metal]

My grand wagoneer did this. The block ground was shot/gone. Would crank, but not hard enough to fire...had to wait, after a little cool down....fired right up. Replaced thar and the problem went away