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Old 10-15-2011, 09:15 PM   #1
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engine cranks but doesnt turn over

Ok so my problems started to progress the last month. as i was driving the engine would shut down. would be able to start it up again no problem. Now she wont start at all. Can crank all day but wont catch. Sometimes she will catch and then shut down a few seconds later. sometimes shell start right away. I know its got to be electrical because the engine wont sputter at all, its as if a ground is loose and someone turned her off. After replacing the coil ive noticed i was getting spark. How come sometimes i get spark and thus the engine fires and sometimes i dont. I have been reading here and most people seem to think its the ignition switch. if it was the ignition switch than why is the starter still cranking?

Tomorrow i am going to direct wire my coil to the battery to ensure that i get spark and see if that will temporarily solve my problems. Has anyone had problems like this before?
Also how do you replace the ignition switch and were is it located (on the column i presume, does that mean i gotta take the wheel off).

i got an 88 wrangler 4.2L manual.

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Old 10-16-2011, 01:33 AM   #2
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It's not the ignition, it may however be inside the column either behind the ignition or down further in the column. I'm a locksmith and I get alot of these in. If the key turns then your ignition is ok. When you turn your key it moves a rod up and down inside the column. There is a very good chance that is broken or close to it. If so, that won't pull up all the way and won't complete the connection. If it is that it is far easier to replace the column then repair it. I would not advise dismantling the column unless you have the proper tools and knowhow, I also get alot of half taken apart columns in. People either break something (didn't have proper tools) loose parts, or can't get it put back together.

If you do tear into it please feel free to PM me for help

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Old 10-16-2011, 09:23 AM   #3
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May be the ECM
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Old 10-16-2011, 09:55 AM   #4
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I had an audi that did the exact same thing, it ended up being a bad mass air flow sensor... but you don't have one of those. Most likely it's just a MAP sensor, which could also possibly be bad.

It isn't he ignition switch. If it turns over and cranks, the ignition switch works.
So, you've got power, it cranks.

There's 3 things to check.

Air, Spark, Fuel

Check fuel by #1 turn the key to the off position, open up your gas cap, use a funnel if you have one, and listen to your tank, have a friend turn the key to the "on" position (not crank it over) you should hear the fuel pump prime with a "bzzzzzzzzzzzzzz" sound.

You should also be able to see the fuel in the carb.

That being said.. I don't think it's a fuel problem.

Sounds like you have spark.

I'm thinking it's an air issue.

If you can get it to run again, before it stalls, get on the gas and see if it keeps running.
If it keeps running and then stalls as soon as you let off the gas, that pretty much all but confirms that MAP sensor is bad.

The other thing to look at is your carb- but they normally don't just magically get out of adjustment.

With the carb, you don't have an engine control computer, and spark is controlled by your distributor, so there isn't much to go wrong there.
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Old 10-16-2011, 11:09 AM   #5
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got it started this morning. she died right after i let off the gas.
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Old 10-16-2011, 12:01 PM   #6
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If you are loosing spark with a 4.2 then you most likely have a bad Ignition Control Module. It's a common problem. It's located under the coolant expansion tank. Most parts stores stock them. Since you have an 88 it's due to be replaced. My 89 4.2 had a similar problem last year. I replaced it and it's been running great since. You don't have a MAP and you do have an Ignition Control Module that controls spark in a 4.2 and you also have an Electronic Control Unit located behind the dash that controls the carb. if you have an original one and a bypass hasn't been done. The back of the carb., again if original, will be "plugged in" to the computer. It's not high tech but if the ICM or ECU fails it won't run. 99% of the time it's a bad Ignition Control Module. All of the other sensors that you might here about are for a 2.5 fuel injection. The 4.2 is very basic but it does have a computer. The ECU usually far outlasts the ICM. You can probably get one for 60-70$.
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Old 10-16-2011, 12:08 PM   #7
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If you are loosing spark with a 4.2 then you most likely have a bad Ignition Control Module. It's a common problem. It's located under the coolant expansion tank. Most parts stores stock them. Since you have an 88 it's due to be replaced. My 89 4.2 had a similar problem last year. I replaced it and it's been running great since. You don't have a MAP and you do have an Ignition Control Module that controls spark in a 4.2 and you also have an Electronic Control Unit located behind the dash that controls the carb. if you have an original one and a bypass hasn't been done. The back of the carb., again if original, will be "plugged in" to the computer. It's not high tech but if the ICM or ECU fails it won't run. 99% of the time it's a bad Ignition Control Module. All of the other sensors that you might here about are for a 2.5 fuel injection. The 4.2 is very basic but it does have a computer. The ECU usually far outlasts the ICM. You can probably get one for 60-70$.
I'll also add that you have a mechanical fuel pump located at the front right side of the engine. Only the 2.5 has the in tank electric fuel pump due to the FI unit. If your fuel pump has failed it's a simple fix. Make sure you note if your inlet line is facing to the front of the engine or rear if you have to get another one. Good luck.
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Old 10-16-2011, 12:49 PM   #8
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Is there any way to know off the bat if your icm is bad? It doesnt look bad but i got no idea.

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Old 10-16-2011, 03:21 PM   #9
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well i ordered the icm for 60 bucks, waiting for the part to come in. Found a ECU for 100 bucks online as well. wondering if i shouldnt jump on that as well. Looking at the picture above, does that look like the original icm? looks a little new to me. just got this jeep couple months ago, so i dont know what is original
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Old 10-16-2011, 04:05 PM   #10
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There is no real world test for it. It's a part you have to replace to rule it out. If it's original it will have a label that indicates AMC. Even if it's not original it could have failed. Unfortunately, it could be a bad ECU, coil or distributor. The most likely candidate is the ICM but it could be something else, including the carb. or in the ignition switch.
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Old 10-16-2011, 06:03 PM   #11
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If i were an ecu, where would i hide in the jeep
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Old 10-24-2011, 10:11 AM   #12
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Just installed new ignition control module for 60 bucks. Jeep cranked right up. Thanks for the good advice i was tired of riding my motorcycle in the rain.

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