Firstly Greetings from Australia... I am New Here.......and ask your HELP!
For the Long Version ....here is some Light Reading http://www.ausjeepoffroad.com/forum/...d.php?t=152937
96 Cherokee Limited Stock......wont start or could possibly start if the planets line up and when it does start it runs perfectly?
Short Version .. this started a few months ago I had to turn the key on and off about 4 or 5 times until the check engine light stoped flashing like a strobe light became normal turned off and the car started once warmed up starting wasn't a issue.....got worse over time and hot starting became a issue.....it finally got that bad (Quickly) it took 10 to 15 on/offs to get it going time to fix it
All Ground wires checked and cleaned .. a small wire in the ones that ground at the oil dipstick was damaged down to 3 of 4 strands ..Repaired Check engine Light stopped flashing
Checked the Relays .. Fuel Pump runs on does not stop after priming....swapped relays did all that
It seems I get no ground pulse from the PCM to the ASD/Fuel Pump.....checked the wire for continuity...0.37 résistance I am now wondering if it is the PCM?
Now when I turn the key on the check engine light comes on for a split second and turns off like a circuit being tripped seat belts gen lights act normal ? since this started I have not been able to scan for codes I get link error message even doing the key thing I cant get codes no check engine light ...? Has the PCM got a crack in the solder on the board a bad wire I am running out of ideas
Thanks for your input

 

Is there any chance there are more issues from the ground wire on the back of the block you mentioned. That location specifically grounds your obd port.

 

I would replace the battery leads and the ground wire from the block to the body at the firewall.
What is are the resistances across these wires?
Maybe the coolant temperature sensor in the thermostat housing is bunk. What are the resistances across this when it it is working and when it isn't working. Also, what are the ambient temperature sensor and how long has it been running provided that you can't get an engine temperature to correspondingly post with the resistances across that sensor.
I like to replace all periodic maintenance parts at times like these. Air filter, spark plugs, spark plugs wires, distributor cap and distributor's rotor. Now would be a good time to add fuel injector cleaner in the system and replace the fuel filter.

 

The check engine light illuminates for a second on startup and goes off as part of the normal operation - presumably so you know that the bulb and system are working.
On my 95 the seat belt light does seem to linger a bit longer than the others before going off.

 

gat all the leads are clean and in good condition.....
I've owned the XJ for five and a half years and done about 10000 k in that time I have changed every sensor. I don't believe it is a sensor issue I checked the voltage on some recently 5v as expected
the pcm is not sending the ground pulse to the asd to turn the fuel pump off after priming

 

Check the wiring harness across the top of the motor? The wires wear out in there because of the heat. Shake it while you're turning it over.

 

I'm mostly just "logging in" cus it's amusing that you guys are really, actually "upside-down" (nutrionows that hit his head, first hit our feet a mil-second later)
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Not to disregard or dis respect the other posts that I may have not read through fully...Do note there is a check valve in the fuel pump that when gone south (Ha ha). We need to repeatedly turn the key on/off, to pressurize the rail to start. Here where we are all "rite side up" we call that the "poor man's prime", A little messy to even think of what goes on down there........

 

New Fuel Pump and Fuel Pressure Regulator in the last 100 klm ....... it is Electrical

 

anyone know how to test a pcm ?

 

No, but if you are having problems with the p.c.m., then you may not have spark. Do you have spark? What is the pressure at the fuel rail? You can "rent" a gauge for free at parts stores.

 

hey gat good fuel pressure 58psi at the rail I have a gauge no spark its not the crank sensor good 5 volt reading
checked for continuity on grey plug C pin 3 to asd 86 0.37 plug 19 to fuel pump relay 86 0.25 so the wires seem ok

 

Yes plug a scan tool in. If it won't connect, bad pcm. Which is my guess anyway but that is what you need to do. Hard to believe you got this far without ever using one to check for codes?? That's like step 1.

 

Code reader wont Link.....Cant get codes via Check Engine Light either?....................Leaning towards a Bad PCM

 

I would guess that at this point you would unplug the terminals from the battery. Read the voltage across them. Unplug the alternator from the system. Reattach the terminals on the batter. Read the voltage across the battery's posts again. Read the voltage across the ends of the terminals and maybe elsewhere. E.g. starter to engine block or positive post to firewall ground.
Try to connect the OBD without the alternator plugged into the system and try to start without the alternator plugged into the system.

 

That would be my vote. I think 96 and 97 are just plug and play, as long as the transmission and 2wd or 4wd is the same. At least thats how it is for the ZJ. no programming of the vin and mileage needed. Many websites will insist on that info anyway, but its not needed. Could actually just grab one from a boneyard and plug it in. I think 98 and up you do need to, though..