Jeep not cranking...

Jerms

New member
My buddies 08 jk is having an issue with the motor not starting. It will zoo and zoo and zoo but won't roll over. We've tried resetting the comp, rolling the jeep back and forth (crank sensor test), park1 park (transmission sensor), but nothing is working. I tried reading a code, but the key test wouldn't even read "done". Any insight would be helpful. At this point, I'm thinking the computer may be at fault...

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My buddies 08 jk is having an issue with the motor not starting. It will zoo and zoo and zoo but won't roll over. We've tried resetting the comp, rolling the jeep back and forth (crank sensor test), park1 park (transmission sensor), but nothing is working. I tried reading a code, but the key test wouldn't even read "done". Any insight would be helpful. At this point, I'm thinking the computer may be at fault...

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If you have another Jeep around that is the same generation as the 08 try swapping computers out so you can give that a test.
 

jims68

New member
You may have issues or lock the other ECM when you switch them. They are married to the VIN number when new. All the modules, ECM, TIPM, BCM all sync with each other so things need to match. I think you would need a virgin module to make this work. It could also be the SCRM module or where your key goes in. Does a code reader work on the OBD port? If not the CanBus is dead which still could be either TIPM or ECM. Make sure you didn't blow any fuses on the TIPM. If code reader works then you may get direction what to look at from the codes. You may get a lot of codes so that will be the trick to sort through them.
 
You may have issues or lock the other ECM when you switch them. They are married to the VIN number when new. All the modules, ECM, TIPM, BCM all sync with each other so things need to match. I think you would need a virgin module to make this work. It could also be the SCRM module or where your key goes in. Does a code reader work on the OBD port? If not the CanBus is dead which still could be either TIPM or ECM. Make sure you didn't blow any fuses on the TIPM. If code reader works then you may get direction what to look at from the codes. You may get a lot of codes so that will be the trick to sort through them.

Have you tried this and had those things happen? I switched ECM's plenty of times in all kinds of cars and never had a problem...

If you need a new ECM, do you have to have even a used one programmed at the dealer before you can use it?
 

hydrohut

New member
Sorry is it just me confused but what does zoo zoo zoo mean? Just can't understand quite what you mean? Is the engine cranking over but won't fire? What state is the battery in? Always good to start with the battery.
 

2013CGJKU

Member
Sorry is it just me confused but what does zoo zoo zoo mean? Just can't understand quite what you mean? Is the engine cranking over but won't fire? What state is the battery in? Always good to start with the battery.

It could also be that the starter isn't actuating correctly. Just spinning but not contacting the flywheel correctly.

It is a pretty vague statement.

Levi

2013 CG JKU 6-speed
 

jims68

New member
On the Chrysler side you are suppose to be able to replace any new module one at a time. My jeep was burned out from an engine fire engine bay forward gone. My problem was after replacing all the cable harnesses and the ECM, TIPM a couple different people told me there was a chance the system wouldn't come up. Robbi at Motech took a used ECM and had his programmer from I think Wisconsin put in my VIN and take out everything not needed for the LS install. Installed everything and a new TIPM and it did come up. Local tech had to fix my SCRM module since the horn wouldn't shut off. The 07 and 08's would go out just from a static shock. He also stated same thing I was lucky. I'm not saying it won't work and if the TIPM is dead probably won't hurt it. If ECM is dead the other one you would think at least would bring the CanBus up. If there is some other problem like a short that could take out the ECM. I bought a spare of EBay for $75 and that might be a safer approach. I wish that there was a simple answer and if I was closer probing around for power at the modules would be where I would start. I have some schematics but not all of them. Just for the 08 model year there were 14 variations to the harnesses and need to be ordered by VIN. Just be careful!
 

jims68

New member
As stated try a different known good battery. Does the dash come up or the radio come up and play? Can you make windows or locks work with switches? What or where is zoo zoo coming from? Did this just appear out of no where or did something else happen first?
 

jims68

New member
Broke basic diagnosing here, KISS! Re-read the first post and dash must be alive since you are trying to pull codes. After trying battery, diagnose the noise. Starter solenoid or relay in TIPM chattering? Do you hear fuel pump cycle when you go to on, not start, with key? Let's start there.
 

Jerms

New member
Everything is working as it should when the key is turned. Lights, dash windows etc. The motor cranks and cranks and cranks (zooing), but does not fire. The fuel pump is working. Again, it does everything it is supposed to do except for turn over. Nothing has happened, no funny sounds or clunks, no CELs, nothing. And I'm not about to pull my personal computer out of my 08 (that runs perfectly at this point) to try it out on his. The battery reads as it should as well. Dern jeep

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jims68

New member
So when you let off of the key it does stop cranking? If so that would leave me to believe the ECM is working, somewhat or may be OK. I would check crank sensor next. If system doesn't see the engine spinning it has no idea how to fire. You may need to check fuel pressure at the rail, but you hear the pump cycle so it should be good??? A good site for instructions to test the crank position sensor is this sit "troubleshootmyvehicle.com". They have a step by step proses since it needs to be tested in vehicle not on a bench. They also have a coil pack test.
 

Jerms

New member
When cranking, you can literally let go of the key and it will continue to try and crank. Is this any indication? ??

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When cranking, you can literally let go of the key and it will continue to try and crank. Is this any indication? ??

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As mentioned, if you let go of the key and it keeps cranking it could be a problem with the ECM. I dunno for sure, but I would imagine it would be hard to pull any codes from the OBD II port if the computer is malfunctioning.
 

jims68

New member
Make sure you are getting fuel either with a gauge at the fuel rail or open the line under passenger side in front of tank. Be careful doing the later option! I don't think the initial pump cycle goes by pressure but by a timed cycle. If there is fuel, CPS sensor checks out then check for spark. With all the cranking you have done aren't you smelling any fuel?
 

JaySC

Member
Not sure if you're having the same problem but when that happens to me, I'll turn the key to the ON position, pop the gear in neutral, and then pop it right back in Park. The jeep starts right away after that.
 

Jerms

New member
Oh yeah we are definitely smelling fuel. The next thing he can check for tonight is if he's getting good spark.

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Jerms

New member
Not sure if you're having the same problem but when that happens to me, I'll turn the key to the ON position, pop the gear in neutral, and then pop it right back in Park. The jeep starts right away after that.

Tried that Jay. Nothing but more cranking...

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jims68

New member
You are on right track. If you have spark there is no reason why it shouldn't fire unless your realy flooded. But leaving it set for a while should of taken care of that. I would still check the crankshaft position sensor. If it doesn't see it maybe it won't fire either.
 
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