CJ 4.2L Starting problem - JeepForum.com

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post #1 of 26 Old 07-05-2010, 02:48 PM Thread Starter
planb722
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CJ 4.2L Starting problem

I have an 86 CJ7 with a 4.2L engine. Went to start it a few days ago and it fired and died immediately it did it 2 more times and now no fire at all. I figured ti was the ign control module so i had it tested and it checks okay. I replaced the ign coil pick up, the coil, cap, and rotor. Still no fire...had a friend convince me it was the module even though it tested okay. Replaced the module still no fire...i've checked the resistance on the coil and pickup. They test within spec. I've got the correct voltage at the coil as well. Even went so far as to run a jumper direct from the battery to the coil. I've checked to make sure there is electricity to the module and made sure it was grounded. I'm at a loss so any help would be much appreciated.

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post #2 of 26 Old 07-05-2010, 02:55 PM
LT1CJ7
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Do you have spark ?
Do you have fuel ?
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post #3 of 26 Old 07-05-2010, 04:00 PM Thread Starter
planb722
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I have fuel but no spark
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post #4 of 26 Old 07-05-2010, 04:36 PM
tigercreek
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When you say "no fire" - do you mean it won't start or that you don't have any spark?

If you pull a plug, ground it and crank does it spark?

Have you check the pickup in the distributor? They can go out and give you a no spark situation.

Just work your way forward or backward in the ignition system to find where you are losing the voltage.

No matter where you go, there you are.
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post #5 of 26 Old 07-05-2010, 05:29 PM Thread Starter
planb722
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no spark...i replaced the pick up coil already
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post #6 of 26 Old 07-05-2010, 10:46 PM
LT1CJ7
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Bad ECM
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post #7 of 26 Old 07-06-2010, 03:52 AM
Lordwrench
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"If you pull a plug, ground it and crank does it spark?"

What tiger said,you never answered.
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post #8 of 26 Old 07-06-2010, 04:38 AM
tigercreek
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If all of your components are testing good you may want to be looking at the connections and/or wiring between them.
Again, start by finding where the voltage falls off with everything hooked up.

LT1CJ7 suggested the ECM. DO you still have it hooked up? Have there been any ignition modifications.

There are a lot of people here that can help you and the more specific information you provide the faster a solution can come.

No matter where you go, there you are.
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post #9 of 26 Old 07-06-2010, 07:58 AM Thread Starter
planb722
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no spark when the i pulled a plug and grounded it...yes the ecm is still hooked up and no i haven't made any ign mods...is it possible to do away with the ecm? I have power going in to the module but when I test the wires going to the pick up there isn't anything. The only part i haven't replaced is the capacitor could that be the problem?
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post #10 of 26 Old 07-06-2010, 08:29 AM
tigercreek
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You can eliminate the ECM. Do a search for "Nutter Bypass"

Probably should solve your problem here first.

How have you "tested" the pickup stator in the distributor?

The stock pickup in the distributor can be tested using an ohm meter.
Orange and purple should show between 400-800 ohms with 600 being nicest between ideal.
Neither of those wires should show continuity to ground.
Replace the stator if anything here is off.

No matter where you go, there you are.
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post #11 of 26 Old 07-06-2010, 04:51 PM Thread Starter
planb722
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i'll retest the pickup and let you know... The only component that i haven't replaced was the capacitor... if it's bad could that be the cause of no spark?
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post #12 of 26 Old 07-06-2010, 05:20 PM
crzdmnky
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NUTTER NUTTER NUTTER! Search for John Nutters bypass in the search button...
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post #13 of 26 Old 07-06-2010, 05:37 PM
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Agreed on the Nutter. It's easy to do if you take your time and understand what you're doing.

Here's the main Nutter how-to

If you need to clean up your vaccum lines after the Nutter, here's the Post Nutter cleanup thread (unofficial)

Here are the before/after diagrams that show the wiring change you make as part of the Bypass. These are simple but explain the wiring change 100 times better than the how-to, IMO:





I had the same problem (only a single spark, and engine wouldn't start). After some troubleshooting and replacing the usual culprits (coil, ignition module), it still wouldn't start. I was going to do the Nutter anyhow and ultimately that fixed my problem.

"I give you a republic, if you can keep it." - Benjamin Franklin
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post #14 of 26 Old 07-06-2010, 05:45 PM
crzdmnky
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Where does the red wire split off to coming from the coil? Just curious
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post #15 of 26 Old 07-06-2010, 06:11 PM
VACJ7
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Quote:
Originally Posted by planb722 View Post
i'll retest the pickup and let you know... The only component that i haven't replaced was the capacitor... if it's bad could that be the cause of no spark?
It is only there to eliminate noise in your radio from the ignition.
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4.2 , coil , ignition module , ignition problem , start problems

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