Help Wit's End... Won't Start

[Infidel Edition]

OK. So when I got back in country, I had to swap the battery and all was good in the world.
Then, about 6 weeks in, on a Wednesday morning, I got in and it cranked but wouldn't fire ~ like it was out of gas.
I jumped on mas transit to get to work and planned on dealing with it when I got home.
That night, it fired up as if there were no issues at all...

Exactly 1 week later, same thing. Crank-crank-crank... no fire. :bang:
That night, worked just fine.
So I picked up another crank position sensor (as its a lifetime from OReilly... its free).
Fired right up.

2 weeks later, parked downtown in a parking garage! :bang::bang::bang::bang::bang:
wouldn't start.
Left it overnight and tried it the next morning as that had seemed to be the solution before - no joy.
* and hasn't fired since

I checked the fuel pressure on the rail and it's 35 / 36 PSI (I believe that's good enough to start...)
I replaced the crank position sensor again... just in case.

3 years ago, I put in a new ecu. I've replaced the crank position sensor. I've double checked all the grounds.
... yes, there is gas in the tank.

There's plenty of juice, the starter is cranking....

It has to be a bad sensor somewhere...
Or someone told me that there is a known "short" spot that zero's out the crank position sensor?... but they couldn't remember where that is.
As far as I can visually tell, the wiring all looks OK.

I'm at a loss.

anyone have ideas on what else I can check?
... I can't drive it anywhere to get it checked as it won't start.

[bluedragon436]

Wow... that's crazy... Does it at least try and fire at all?? Like does it kind of studded, like it is trying to fire over?? Or odes it just keep turning over and over, w/ no attempt to even fire (like no spark??)

[OldFaurt]

OK. So when I got back in country, I had to swap the battery and all was good in the world.
Then, about 6 weeks in, on a Wednesday morning, I got in and it cranked but wouldn't fire ~ like it was out of gas.
I jumped on mas transit to get to work and planned on dealing with it when I got home.
That night, it fired up as if there were no issues at all...

Exactly 1 week later, same thing. Crank-crank-crank... no fire. :bang:
That night, worked just fine.
So I picked up another crank position sensor (as its a lifetime from OReilly... its free).
Fired right up.

2 weeks later, parked downtown in a parking garage! :bang::bang::bang::bang::bang:
wouldn't start.
Left it overnight and tried it the next morning as that had seemed to be the solution before - no joy.
* and hasn't fired since

I checked the fuel pressure on the rail and it's 35 / 36 PSI (I believe that's good enough to start...)
I replaced the crank position sensor again... just in case.

3 years ago, I put in a new ecu. I've replaced the crank position sensor. I've double checked all the grounds.
... yes, there is gas in the tank.

There's plenty of juice, the starter is cranking....

It has to be a bad sensor somewhere...
Or someone told me that there is a known "short" spot that zero's out the crank position sensor?... but they couldn't remember where that is.
As far as I can visually tell, the wiring all looks OK.

I'm at a loss.

anyone have ideas on what else I can check?
... I can't drive it anywhere to get it checked as it won't start.

smack the relay box (not hard enough to break) in the engine bay and try again. If that works, start replacing the relays involved with engine management starting with the shut down relay! Relays get oxides on contacts when the sit around for long time & that makes them work "sometimes". Also, disconnect the ECU connector and re-connect. Similar problem. Also check you ignition switch module, they roach but are very cheap to replace!

[Infidel Edition]

No..... Just crank but no sputter
Like there's no spark

[4.3LXJ]

Have you checked to see if you have spark?

[Infidel Edition]

I'll try that when I get home.
I've replace the starter relay (few years ago) but will double check connections there too

[4.3LXJ]

The starter relay is OK if it turns over. But you should check the ASD relay and make sure it works

[denverd1]

had a similar issue. replaced CPS and a few other things. ended up being a fuse in the passenger side fuse panel. Had no idea there was even fuses over there.....

worked intermittently like yours then just crapped out one day and didn't fire for 6 months till I finally put it on a trailer and took to an auto electrical shop. felt pretty stupid to say the least

[Infidel Edition]

I'm 98% sure I don't have any fuses on the passenger side. Mind's an 89 stick

[NW99XJ]

ASD is the likely cause.
OLDFAURT gave good advice.
But I would also start by verifying you have (or do not have) spark at the plugs.
You can do this bu pulling the plug wire from the plug and stick a screwdriver into the end of it, then while someone tries to start it hold that screw driver real close to ground but not touching, you could also pull the whole spark plug too, and hold the threaded side to ground, and have someone crank. You'll be looking for a spark.
No spark = no juice. And likely an ASD relay issue.
Good luck.

[bruggz351]

Wow.
This is what mine is doing, intermittently.
I've replaced CPS, the throttle body and associated sensors. Cam angle sensor(the plate in the distributor).
I thought it was fixed. But all of a sudden it played up for a moment on ONE day.
Again, it's been ok, since. ????
I have swapped relays around in the power distribution centre. No change.

One thing though, I have found in my situation, if I use some throttle while turning it over, it will cough and splutter into life. It takes a while to get to idle, but it eventually gets there, after a lot of spluttering.

Also, if I just stay on the key, turning it over and over and over it will eventually start, albeit with a very rough idle and black (fuel) smoke.

It's got me stuffed!!!

cheers

[OldFaurt]

Wow.
This is what mine is doing, intermittently.
I've replaced CPS, the throttle body and associated sensors. Cam angle sensor(the plate in the distributor).
I thought it was fixed. But all of a sudden it played up for a moment on ONE day.
Again, it's been ok, since. ????
I have swapped relays around in the power distribution centre. No change.

One thing though, I have found in my situation, if I use some throttle while turning it over, it will cough and splutter into life. It takes a while to get to idle, but it eventually gets there, after a lot of spluttering.

Also, if I just stay on the key, turning it over and over and over it will eventually start, albeit with a very rough idle and black (fuel) smoke.

It's got me stuffed!!!

cheers

Idle speed actuator? though rare, they do die! Try removing the harness from the ECU in the engine bay and then re-install! Might just be a bad connection thing!

[bruggz351]

Idle speed actuator? though rare, they do die! Try removing the harness from the ECU in the engine bay and then re-install! Might just be a bad connection thing!
Thanks OldFaurt.
Could be a bad connection. I've changed the entire throttle body, from a known good running engine.
I'm also slowly coming to the conclusion, that this new xj has been under water, dirty water, for a time. Maybe even a flood vehicle.
So I'm banking on quite a few electrical problems, raring their ugly heads, in the not too distant future. [emoji24]
I'll have to go through, methodically, all the connections, cleaning.
Might try another PCM/ECU, also.

Sent from my FRED

[OldFaurt]

Thanks OldFaurt.
Could be a bad connection. I've changed the entire throttle body, from a known good running engine.
I'm also slowly coming to the conclusion, that this new xj has been under water, dirty water, for a time. Maybe even a flood vehicle.
So I'm banking on quite a few electrical problems, raring their ugly heads, in the not too distant future. [emoji24]
I'll have to go through, methodically, all the connections, cleaning.
Might try another PCM/ECU, also.

Sent from my FRED

Mine was a mud dunker... I cleaned all of the connectors and then applied dielectric grease to keep out oxygen and moisture and got pretty good results. I did replace the ignition switch down on the steering column, some of the terminals had melted from a previous short. the switch was about $25 and fairly easy to replace. It's attached to the top of the column above where you feet are when driving. There is a rod that comes down to it from the switch to operate it.

[bruggz351]

Mine was a mud dunker... I cleaned all of the connectors and then applied dielectric grease to keep out oxygen and moisture and got pretty good results. I did replace the ignition switch down on the steering column, some of the terminals had melted from a previous short. the switch was about $25 and fairly easy to replace. It's attached to the top of the column above where you feet are when driving. There is a rod that comes down to it from the switch to operate it.
Excellent.
I haven't heard of the switch further down the column. I shall look for it.
And purchase some dielectric grease.

Thanks man, for the help.

Cheers

Sent from my FRED

[Infidel Edition]

So I went to replace the stater in the disrto.
And noticed the cap and roter were crap... Cap+rotor+stater = more than a new distributor
So I replaced the entire distributor
Ran perfect around the block twice ... And if anything a little low at idle after getting to temp.

2 days later, starts runs strong till it hits temp... And then low rpms at idle. Like almost gonna die low.

When I pulled the old disrto (engine never moved) I couldn't get the rotor to the exact same.point. was like 5-7° more clockwise. And the disrto housing doesn't rotate...
The low idle is almost like the timing is off ~ which is what I'd expect with the rotor advanced....

And back to the won't start. Crank and crank....
Can you adjust the timing on the 89 4.3?
~ guessing I need to rotate the disrto housing to compensate...

Haven't tried the asu relay yet.
Maybe in a day or 3/when I get a moment.

[denverd1]

I know nothing of the early systems on cherokees, but if it's like any other old school dizzy and timing system, yes you can rotate the diz to set timing. Grab a timing gun and dial it in. Sounds like that's your issue.

sent from my Samsoon S5 from the bottom of a mud hole

[4.3LXJ]

The 4.0 is a combo of old and new school. It is non adjustable. The timing is actually adjusted by the ECM. But, Cryco ECMs are kind of stupid and fussy. The dizzy needs to be spot on. When you pull the dizzy, use a screw driver to adjust the oil pump drive so you can move it one tooth. That will probably get it

[denverd1]

The 4.0 is a combo of old and new school. It is non adjustable. The timing is actually adjusted by the ECM. But, Cryco ECMs are kind of stupid and fussy. The dizzy needs to be spot on. When you pull the dizzy, use a screw driver to adjust the oil pump drive so you can move it one tooth. That will probably get it

so its the same as on my '98. Yup, get that crank and oil pump oriented just right (pointing to 10 o'clock as you face the right side of the block IIRC) and drop it in. There's only 1 position it can be in. Took me a few tries to get it there and it won't fire unless its pretty close to perfect.

[4.3LXJ]

On the one we just set up here we used the 4 o'clock position

[denverd1]

On the one we just set up here we used the 4 o'clock position

sounds like it would be just opposite the aforementioned 10'oclock position and work just fine!

[Infidel Edition]

Think I FINALLY figured it out.
The timing was actually good.

So on a wild hair :rolleye0018: thought. I rechecked the TPS voltage.
Rather than the 0.84 that I had set it to... it was 0
I loosened the screws and reset it. AND left the meter connected as I tightened it. And noticed that when I tightened the screws back down, it would go back to 0 :bang:

SO I picked up a replacement... same issue.

If I leave it lose enough to adjust to the .84 it starts and runs great.
But I can't tighten it.

Maybe there's some missing washers or something that is causing it to flex ever so slightly. :smiley-scared003:

Will try again when it's not raining...

[4.3LXJ]

Well, you are getting closer anyway

[Infidel Edition]

Every little bit counts!
:bacondance: