1993 Base Model won't fire - JeepForum.com
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post #1 of 31 Old 07-10-2016, 08:58 AM Thread Starter
Taz360ZJ
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1993 Base Model won't fire

so my ex called me yesterday frantically to tell me the ZJ won't start, I met up with her, did some quick diagnostics:

the ZJ is a 1993 base model Special Edition SE/Sport, 4.0L, 231, 42RE, 113,000 original miles, factory keyless, no OEM alarm, added crimestopper remote start, federal emission, USA built, Feb 1993 MDH.

Turns over normally, has lights, 12.63v on the battery according to my DVOM. It's getting fuel (Napa gold filter was new with the new Bosch fuel pump in the fall of '15 along with the second tank cleaning), nice stream shot out of the schrader when cranking, I fixed the FPR elbow with a new one (noticed the old one was brittle and the line broke on it), sprayed some brake cleaner down the intake, didn't even sputter on brake clean, it's got nice blueish white spark, I pulled the battery terminals and cleaned them, I even jumped the negative terminal right to the block grounding point with my jumper cables with same results, swapped the ASD with the starter relay, popped the cap off and inspected the condition of the cap and rotor and play in the distributor shaft all seemed normal, it had spark as the compression stroke was coming up right on time, the crank sensor was a new OEM Mopar sensor from the dealer in the fall of '14 (the reason it wouldn't run when we bought it), it's got new timing/tensioner/balancer/FMS as of just after Halloween/early November, new NTK O2 last fall the wiring and harness looked good and unchaffed, the PCM had the same 12.63v at the power in pin, the PCM ground was good and tight on the battery, the plugs (tune up September '15) were semi wet when I yanked them, I shook all the looms and looked at them for rub through, every fuse in the PDC had power across the terminals with the key in the battery position, I wiggled the main PCM plug while she cranked it over. Nothing worked. I have custom battery cables that are 4 gauge welding cables, crimped soldered heavy wall shrink on the ends with lugs. I already did the ground terminal mod on the block with marine style battery terminals, and grounded the new 136A 5.9 alternator right to the grounding point on the block, the grounds on the block looked good.

I'm stumped, theoretically it should run, it's got air fuel spark, no I didn't throw a pressure gauge on the rail, or noid light the injector harnesses, 12 and 55 from the PCM. My ex said she parked in a spot, shut it off, realized she was in the wrong parking lot, started it back up.....had a longer than normal crank time, moved to a new parking lot. The ZJ sat for 4 hours or so, she came back to it, and it just cranks but not fires. This is the first major issue we've experienced with it, it's been amazingly reliable all this time since the rebuild from late '14 - late '15, first time we've had it towed.

Bad PCM? I can't think of anything else that would really cause this issue.


'94 ZJ, AX15, UC+BB, Ravine's, 31's, 3.8L fan, D2S's, fully murdered out.
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post #2 of 31 Old 07-10-2016, 10:30 AM
ZeeJay1997
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You've pretty much covered the bases except reference voltage for the sensors. Throwing some ideas out...

IIRC the crank and cam sensors should have 8v and 5v to the TPS and MAP. If any of those are missing it could be a bad PCM or a shorted sensor.

Disconnect TPS and get on the two outside connector contacts with your meter. This verifies sensor ground and sensor 5v are available from the PCM. PCM would normally kick out a code if this voltage is missing, but maybe that part of the PCM is tango uniform.

If the 8v were missing or shorted it wouldn't fire.

There's a no start section in the dirty dozen linked below. Run through the procedure that #dellis wrote (link provided in dirty dozen)


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post #3 of 31 Old 07-10-2016, 10:33 AM
HighLonesome
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Considering all you have done, the first thing I would do is eliminate the aftermarket electronics.
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post #4 of 31 Old 07-10-2016, 10:46 AM
PolkaPower
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Quote:
Originally Posted by HighLonesome View Post
Considering all you have done, the first thing I would do is eliminate the aftermarket electronics.
ZJ's don't like those kinds of alarms or starters. A lot can go wrong.
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post #5 of 31 Old 07-10-2016, 11:31 AM
xcaliber81
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Derp nm.
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post #6 of 31 Old 07-19-2016, 02:52 AM Thread Starter
Taz360ZJ
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Update:

used PCM proved no difference, part numbers matched, new stock style champions, timing is good TDC seemed to be spot on, the iac and tps had voltage,

I'm out of ideas.

'94 ZJ, AX15, UC+BB, Ravine's, 31's, 3.8L fan, D2S's, fully murdered out.
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post #7 of 31 Old 07-19-2016, 04:00 AM
Zilliver
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Check the CAM sensor condition

95 Grand Cherokee 5.2
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post #8 of 31 Old 07-19-2016, 05:43 AM
PolkaPower
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Quote:
Originally Posted by Zilliver View Post
Check the CAM sensor condition
Yeah that's rare to have malfunction but it will cause a no start situation.

Did you ever remove the alarm?
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post #9 of 31 Old 07-19-2016, 06:20 AM
Zilliver
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Yes, it will cause a crank but no start symptom.

95 Grand Cherokee 5.2
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post #10 of 31 Old 07-19-2016, 06:36 AM
Eagleputt13
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I would check the ignition coil first and double check your fuel pressure. I had same symptoms with low fuel pressure aka bad fuel pump assembly.

Mike

Beep beep, who got the keys to the Jeep? V-r-rrrrrrrooooom!
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post #11 of 31 Old 07-22-2016, 12:53 AM
DW2296
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Batteries can be dead but still give normal voltage. There's a method which involves connecting an external resistor to help measure internal resistance of the battery. Basically, they just can't put out enough power anymore for certain needs.

However, I don't have much experience/knowledge about car batteries. They might work differently. If it turns over, it may be fine. To be sure though you could connect a battery charger, put it in "start" mode, and see what happens.


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post #12 of 31 Old 07-22-2016, 09:15 AM
dellis
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I am going to provide you with a couple of diagrams I developed for ZJ's that might be helpful. In the first diagram, the purpose is to figure out which of the three major causes of no-starts is responsible. A sudden no-start is fuel, spark, or timing (ASD and PCM stuff).

The second chart would be used if you think your issue is with the timing portion of your Jeep. It shows the things that must be functioning in order for the Jeep to start plus the five key diagnostic points that you should test and verify.

What you haven't eliminated.
  1. If you are convinced you have good fuel and good spark, then you should focus on the timing issues that pass through the ASD. From what you've written, I don't see that you've tested for functionality of the ASD or for sensor shorts ... these are quite common no-start issues for the early model ZJ's.
  2. Second, that remote starter and non-OEM alarm should also be highly suspect. I would get those out of the system so that they can be eliminated as potential causes.




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post #13 of 31 Old 08-26-2016, 11:01 PM Thread Starter
Taz360ZJ
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Not much to update, I was curious if the timing was off at all, so at my wits end I pulled the timing cover off with my ex helping me. nope....the timing is still set and good from the time I did it in early November '15....new set and tensioner verified spot on and in place. So her dad got upset that she was borrowing their Trailblazer to get to work during the week, he said it's going to the dealer. well she got it towed to the dealer, it sat for a couple days, they had it for a week+ looking at it, every tech had a crack at it, and they came up with.......the same thing I ran in to....a road block. they verified everything I did, PCM voltage, continuity, timing, sensors, fuel pressure. It's still getting intermittent spark....has it...won't fire....spark goes away for no reason. So we are back to square one, the Jeep is back at her place.
I'm thinking the problem is in the PDC box or in the loom, definitely electrical at this point. It sat in Texas for 10 years at my friend's parents house by their garage out in the open. It had critters in it here and there, I've had to solder in a couple wire pieces for the wipers and fuel pump; it wouldn't surprise me if they chewed a wire somewhere and it finally grounded out or broke. My ex is looking at buying a newer car soon, I'm not sure on the fate of the '93 SE now, I want to go poke away at it, it's something simple somewhere...has to be. But she may just sell it whole for parts as a non running vehicle. Would make a good candidate for a GM LS swap with the AX15 behind it.

'94 ZJ, AX15, UC+BB, Ravine's, 31's, 3.8L fan, D2S's, fully murdered out.
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post #14 of 31 Old 08-27-2016, 07:03 AM
ZeeJay1997
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What were the results of the diagnoses that Dellis posted? And did you get rid of the aftermarket electronics?


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post #15 of 31 Old 09-01-2016, 09:58 PM Thread Starter
Taz360ZJ
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Well...small update....looks like I'm coming back! Buying the '93 off of her for cheap, as-is, non running. Tags expired, can't be moved, the cops will eventually ticket it, impound it, and crush it....yes even on private property they do that here. I'm towing it behind my Ram to a friend's house out of town in the country within a couple weeks to begin the diag process on MY JEEP....not hers.


Quote:
Originally Posted by ZeeJay1997 View Post
What were the results of the diagnoses that Dellis posted? And did you get rid of the aftermarket electronics?
I'll tell you what, I screwed around with it for 2 months on and off after work, when I had time, I hardly checked in here while I was working on it. I will definitely be printing off all these procedures and going over it AGAIN in more depth, and let you know.

yes I unplugged the remote start, it had no effect on anything.....and no it's not an alarm system, just a remote start/keyless entry....no ignition kill anti theft.

Looks like I may be 5 speed swapping this ZJ after all

'94 ZJ, AX15, UC+BB, Ravine's, 31's, 3.8L fan, D2S's, fully murdered out.
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