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Classic "jeep won't crank" issue - 2001 Wrangler Sport, 4.0

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Hi Richard, classic "jeep won't...
Hi Richard, classic "jeep won't crank" issue - 2001 Wrangler Sport, 4.0 liter auto trans. Starter, solenoid, relay, fuses are all good - I even replaced the ignition switch to no avail. there's no power at the brown ignition wire going to the solenoid. I can jump the terminals and it starts right up. Also, if I pull the starter relay and jump terminals 30 and 87 it cranks just fine (though I haven't turned the key to "start" to see if it'll run - I didn't see the need to). It's looking to me like I',m not getting ground to the PDU just on that one terminal (86 I believe). If that's the case, I'm at a loss as to where to look for a broken connection...
Submitted: 2 years ago.Category: Jeep
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Answered in 4 hours by:
8/29/2015
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago
Amedee
Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 26,786
Experience: ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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Hello and welcome! My name is ***** ***** I would like to assist you with your question. Would that be OK or would you rather wait until Richard comes on line?

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Customer reply replied 2 years ago
It doesn't matter to me who provides the solution.
As a follow-up since I submitted the inquiry, I removed the PDU to gain access and inspect the wiring underneath and it's all immaculate/factory with no evidence of dirt, corrosion, or anyone being in here before me. I tested continuity from the wire (#87 in the starter relay) to the solenoid on the starter - thicker brown wire - and there's continuity. This is a big relief to me, I thought I'd be chasing a broken wire somewhere. However, I'm unable to determine if # ***** has ground. Everything is very clean and original so I'd be extremely surprised if there was a "broken" wire or corroded connection somewhere. (but I suppose it's possible, everything I've tested so far is good)
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Ok, I would love to help you out! This will be easier than you think. With the starter relay removed, have an assistant hold the key in the CRANK position while you check for two powers going into the female pins of the starter relay. One power comes from fuse 8. It is a 40 amp fuse in the power distribution center under the hood. The other power to the relay comes from the ignition switch and then goes through the 20 amp AT fuse before coming to the starter relay.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

If that checks out good and those tests pass, then yes, you are correct. Chances are there is no ground going to the starter relay. The ground comes from the park nuetral position switch when the transmission is in park or nuetral.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

I am glad I can help! Please dont forget to honor your good faith deposit by rating my answer as "excellent service" for assisting you today.

It has been a pleasure working with you!

Amedee

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Customer reply replied 2 years ago
Hi Amedee, thank you for the messages, I'll run/re-run the rests in the morning to confirm, and then look into the park nuetral position switch. however, based on the diagram it's hard for me to tell which part of the engine this is located (can you tell I'm not a technician? :)) Which side of the Jeep and general are am I starting at to locate the park nuetral position switch? And when I locate it, is the solution to replace it or can it be cleaned/adjusted? Based on the forums I've been reading this week, I suspected it was the "neutral safety switch" -- is this the same thing as the park nuetral position switch in the diagram?
Thanks again!
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Good morning! YES, the PNP switch is the same thing as the nuetral position swith. The diagram is a picture of the transmission with the transmission pan removed. I will see if I can get you another picture.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

I cannot seem to find a picture.. however, this switch is located on the left side of the transmission

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Customer reply replied 2 years ago
Oh, so this requires removal of the transmission (pan) to fix? Is there any way to temporarily bypass it to verify that this is indeed the issue?
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

YES, you would just ground the wire going to the PNP switch and see if the engine will then start

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Customer reply replied 2 years ago
I'm going through the instructions that you sent yesterday and there is no 40A fuse in position 8 -- this position is blank (confirmed with the service manual). I'm not sure if this is a critical point though, seeing that (if the diagnosis is indeed the Neutral Safety Switch) I'll likely be requiring a dealership anyway.
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Hello! If there are two powers going to the starter relay pins or cavities with the key in the crank position, all of the fuses for the starting circuit are good. That is why I am having you check this.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

In addition, I am not telling you what is wrong with the vehicle.. because I am not there doing the testing myself. I am telling you how to diagnose it so that you can pinpoint the problem.

Right now, we dont know if the PNP switch is bad... hence the testing we need to do to get us to that point. Does that make sense?

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Customer reply replied 2 years ago
Got it, that does make sense, thanks - we're still determining that the PNP switch is indeed bad. Also it appears that this does not require removal of the transmission pan to replace so that's a relief.So here's my confusion ( and I may have missed it but I have read through our exchanges several times) I can test the 20 amp AT fuse but there is no 40 amp fuse as position 8 in the PDU. It's not noted in the service manual and there's only a single connector/blade in the port. Is the number 8 position correct?
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Are you sure you are looking in the power distribution center under the hood?

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

If so, then something is not adding up. According to the information you gave me, that is the correct wiring diagram. But again, I would not be too concerned about it as long as there is two female pins at the starter relay with the key in the crank position. That is the important part.

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Customer reply replied 2 years ago
I'll attach a couple of pictures, one of the diagram and one of the actual fuses (and the empty #8 slot). I checked underneath the fuse "board" where the individual wires connect and confirmed there's nothing going to the #8 fuse port - says it's for ABS motor. In any case, I verified the 20 amp fuse behind the glovebox and also replaced it with a new one for good measure. I'm going to test the PNP switch for continuity according to the service manual and go from there, hopefully I can isolate the cause of this whole issue. Thanks again. If there's anything I can do to confirm the PNP switch to be good/bad please let me know and I'll give it a try while I'm trolling around in there :)
Customer reply replied 2 years ago
One other question (I apologize for the spam), when you say "ground the wire going to the PNP switch and see if the engine will then start" I'm not certain how to accomplish this. Should I be connecting a jumper wire from something on/in the switch to the negative battery cable? I'm not sure what to ground (I believe there are two wires in there)
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Hello! Do you see the wiring diagram I have attached? The brown/light blue wire is the wire coming from the PNP switch. Again, all you need to do is disconnect this connector going to the PNP switch and ground this wire and see if the engine will start. If so, then you have verfied all of the other wiring in this circuit as working good or OK. That would only leave the PNP switch provided there is no internal transmission problems.

To do this, just run a jumper wire from this brown/light blue wire to ground. You could run it to battery ground or the side of the transmission case as this should be ground.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

By the way, it would be fuse number 6 in your PDC. It is labled starter.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Now my wiring diagram could be wrong. If you send me your VIN, I will double check for you.

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Customer reply replied 2 years ago
Super, thanks for the follow-up information, I'll be able to do that but it may be later today. Please don't feel compelled to standby your Inbox, this is a recreational Jeep so it's not super time sensitive (and I know you have a life outside of answering technical mechanical questions :-)) The VIN is 1J4FA49S71P314332 but at this point I'm thinking the position of the starter fuse isn't critical because I can jump #30 and #87 on the starter relay and the engine cranks over so I'm pretty sure the rest of the circuitry is ok. (but again, I'm pretty stupid with this stuff yet!)
Thanks again Amedee, I'll keep you posted, likely later today or this evening. No hurry on the replies either, you've been helpful thus far and my testing assignment could take a little while.
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Sounds good, I am out running around now. Will check back with you a little later today.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Click on the link and you will see fuse number 6 is the one that powers up the starter relay. Not fuse 8 as in the other wiring diagram I sent you.

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

So sorry about that. Now everything is making sense and matching up to your pictures you sent me

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Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Let me know when you are back on line and we can continue.

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Customer reply replied 2 years ago
Hi Amedee, thanks for your patience. I had a heck of a time finding the PNP believe it or not. On the 2001 Wrangler it's tucked up behind the drive shaft - once I realized I was looking for a violet/white wire (new diagram - thx BTW) vs. brown/lt.blue it was much easier. However, jumping a wire between the center hole and a solid ground still doesn't allow the engine to crank. I have 12.64V power to the 40 amp fuse in the #6 position in the PDU, and I can crank the engine over by jumping #30 and #87 in the starter relay. This is perplexing, I'm about ready to give up, I really don't know what else this could be. I purchased a neutral safety switch, I'm thinking I might as well replace it while I've got everything cleaned up and apart down there. Any other ideas? Again, no hurry, I know you've already done your share of advisement and are probably tired of this as well.
thanks again Amedee..
Jeep Mechanic: Amedee, Jeep Technician replied 2 years ago

Maybe we should talk on the phone. That would be easier

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Amedee
Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 26,786
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Experience: ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector

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