96 ZJ only runs with one spark plug out - JeepForum.com
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  • 1 Post By zjosh93
  • 1 Post By V8GCZJ
  • 1 Post By RayChrlesBrkley
 
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post #1 of 10 Old 06-14-2021, 10:42 AM Thread Starter
RayChrlesBrkley
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1996 ZJ 
 
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96 ZJ only runs with one spark plug out

Hello,

My 96 ZJ with the 4.0 liter in-line 6 has been sitting for about 2 years. I did the following to work towards starting it:

Replaced wires, plugs, rotor, rotor cap, battery. Triple checked firing order and wire routing.
Used a shunt on the fuel pump relay to ensure the pump and filter are in decent shape and to drain out the old fuel.
Added 2 gallons of new fuel.
After that it turned over, but only ran for a few seconds with a bit of starting fluid.
Then I pulled plug #2 and put the wire back on it and grounded it.
Then I cranked it, plug #2 sparked, and then the engine began to run with only 5 plugs. It sounded like an old steam engine with one plug out, and it didn't run well, but it ran, unlike it did with all 6 plugs. I didn't try it with any other plugs out, but I pulled the plugs to make sure it isn't flooded and I'm waiting until next week for the next round of battle.

Any suggestions on next steps?

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post #2 of 10 Old 06-15-2021, 07:38 AM
zjosh93
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Join Date: Aug 2010
Location: Austin
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My guess is that it was just unhappy from sitting very long. You started it with all the plug wires and it stalled, which is normal for starting a vehicle that has sat. Then you cranked it with the plug wire off and it started and ran. I'd bet if you had just tried to restart it it would have run fine on all 6. The engine will start an run on surprisingly few cylinders.
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post #3 of 10 Old 06-15-2021, 09:23 AM Thread Starter
RayChrlesBrkley
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Quote:
Originally Posted by zjosh93 View Post
My guess is that it was just unhappy from sitting very long. You started it with all the plug wires and it stalled, which is normal for starting a vehicle that has sat. Then you cranked it with the plug wire off and it started and ran. I'd bet if you had just tried to restart it it would have run fine on all 6. The engine will start an run on surprisingly few cylinders.
Do you think I may have flooded it? At one point it turned over and ran with all plugs in, but that was a few rounds ago and it hasn't done so since.
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post #4 of 10 Old 06-15-2021, 12:47 PM
zjosh93
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Doubtful. Flooding to the point of not starting is somewhat unlikely with the EFI. What does it do if you tray and start it right now with all the plugs in? Are there any codes in the computer?
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post #5 of 10 Old 06-15-2021, 11:02 PM
V8GCZJ
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Quote:
Used a shunt on the fuel pump relay to ensure the pump and filter are in decent shape and to drain out the old fuel.
After you put fresh gas in the tank you should have purged the old gas out of the line(tank to injectors). You may still have bad fuel in the line.
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post #6 of 10 Old 06-17-2021, 02:05 PM Thread Starter
RayChrlesBrkley
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I failed to mention that I pulled the fuel rail and emptied it. Would my next step be to check the injectors? I mean, I know they work because at one point during round 2 or 3 it fired, as discussed above. When it did fire, I was able to rev it and it sounded perfect at 3.5k RPM, but died on the come down. Do injectors get clogged in a situation like mine where I tried to turn it with the bad gas prior to draining it?
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post #7 of 10 Old 06-17-2021, 02:09 PM Thread Starter
RayChrlesBrkley
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I forgot to say that I also shunted the pump circuit to get fresh fuel in the line once the tank was empty. Then I used the schrader valve to bleed at the rail. After trying to start it, opening the schrader valve resulted in a heavy stream of fuel with no more air.
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post #8 of 10 Old 06-18-2021, 04:51 AM
V8GCZJ
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Quote:
When it did fire, I was able to rev it and it sounded perfect at 3.5k RPM, but died on the come down.
How long did you run it? And at what rpm did it die or did you let off the gas? If it will run with you foot on the gas but not by itself it could be the IAC.
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post #9 of 10 Old 06-20-2021, 09:12 AM
95-ZJ
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You have the requirements for combustion = clean, new fuel, a good working fully functioning ignition system, and a clean fully unobstructed air filtration system. IMO, from my experience, if, after doing everything you said you did it is not starting at all, it is most likely, an electrical or fuel delivery based issue. I read all your comments but want to ask if you have replaced the coil as well? Also, check all GROUNDS, to/from the chassis/body and from battery. A simple loose wire that can be traced and tightened, may also be a contributor (and its a good idea to tighten all GROUND contact points on any "new to you" vehicle) Since its a 96, do you have a OBD2 code reader? If not, it would benefit you to get one. Then, having borrowed or bought one if you do not own a scan tool, run a complete diagnostic scan and check all codes to see if you can further diagnose the current problem and remedy it.

Last edited by 95-ZJ; 06-20-2021 at 09:19 AM. Reason: Added info. Corrected spelling
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post #10 of 10 Old 06-20-2021, 03:42 PM
JaimeZX
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1995 ZJ 
 
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Crank Angle Sensor? When that died on my Dodge ram I had symptoms similar to what OP is describing.

HID Projector retro! https://www.jeepforum.com/forum/f13/hid-projector-retrofit-build-thread-3082289/
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