dakota32580

I drive a 2008 Jeep Wrangler Rubicon and sometimes after it sits, it won’t turn over. For some reason to get it to start you have to push the transmission further into park, hold it there, then turn the key and it starts right up. We’ve taken it to the dealer multiple times and once even paid a lot of money for them to fix it and it’s not been fixed yet. Does anyone know what’s wrong with it and how to fix it?

ronjenx

When this happens, do you hear a "click" when you turn the key?

dakota32580

Yeah it kind of tries to turn over but can’t fully do it

ronjenx

That sounds a lot like the "click- no start" problem quite a few people have had, especially with the early automatic JKs.

Try running a heavy ground wire from the alternator mount bolt to the battery negative terminal. That has solved the problem for a lot of people.

resharp001

I can't help with the issue, but following along out of curiosity. I was originally thinking it sounded like maybe something in the transmission cable linkage.....like the vehicle is in "P", but you're having to hold the shifter with a little pressure for the computer to recognize it's in "P" in order to crank. Ronjenx, is there some sort of sensor that determines the location of the shifter, or is that all mechanical? This is not an area I've had to explore on my jeep.

ronjenx

With the 42RLE, it's mechanical from the transmission lever to the transmission range sensor, which is inside the transmission, awash in transmission fluid. It's possible the linkage/cable is out of rig, but usually it's a loss of good contact at the range sensor. That loss of good contact can be caused by inadequate engine/transmission grounding.
Here's the sequence of events as I understand it:
The transmission lever is in the Park position.
The transmission range sensor contacts are arranged properly to tell the computer the transmission is in Park.
The key is turned to Start.
The starter relay is allowed to close.
A jolt of electricity tries to go to the starter, but because of inadequate engine/transmission ground connections, some of that jolt finds its way through the transmission range sensor contacts.
The jolt through the sensor contacts causes a loss of continuity to the computer, which brings the start sequence to a halt because the computer no longer sees the transmission as being in Park.
Moving the lever to Neutral, or even further into Park, moves the range sensor contacts enough to reestablish continuity, and the JK is allowed to start.
The addition of a large ground wire from the alternator mount bolt to the battery negative terminal prevents this problem. Adding another one from the engine to the transmission helps, too.

If the OP has the usual click-no start issue, this will help.

resharp001

You're a wealth of information Ronjenx! Thank you for that thorough explanation.

EHarris

I owe him lat least 40 beers.

OnBelay

All of this, 100%. The JK grounds are very weak, and the whole JK will benefit from adding additional grounds, and running grounds parallel to existing grounds wherever possible. Oh, and cleaning ground points and applying conductive (NOT DIELECTRIC) grease, etc. You'll amazingly have faster starts, less noise on your HAM/CB radios, and your lights won't dim when you turn the engine over.