Sorry for the funky title, apparently we have limited characters to use in the title here lol

Anyways, so this past weekend I was in the mountains as usual, did some hiking with my son and when we were headed back down the forest road, I stopped because I had to pee. Thank god I stopped when I did, I walked around the front of the jeep and it was puking trans fluid. Somehow managed to pull off one of the trans cooler hoses near the radiator. I was able to reattach it but naturally didn't have any trans fluid with me. I always have oil/cooilant/tools etc but since we were just going for a hike I didn't have trans fluid the one and only time I've ever needed it lol.

Thankfully I was still able to manage driving back down the mountain which was about another 20 miles of **** dirt road and then another 20 miles or so to the nearest town with an autozone that I could grabs trans fluid and top it off. I noticed on the drive there that the trans was slipping a bit, but that was to be expected. Once I topped off the trans fluid it was running/driving just fine like normal.

Fast forward to yesterday morning when I was trying to leave the house, went out to the Jeep to fire it up and it cranked for a split second then stopped. I thought that was strange so I tried looking things over real quick and didn't see anything obvious. Ended up having to work from home (thankfully I was able to). Got done with work and went back to play with it a little more. After a little process of elimination such as swapping around the ASD/Relays etc to rule those out, I was able to turn the ignition on and jump under the jeep to arc the starter. As soon as I did that it fired right up and I even drove it around for about 10 miles and it ran fine. Once I got home, it didn't restart with the key again, not that I expected it to.

At this point my initial thoughts were that it's the ignition switch, but I have other people telling me that it could still be the NSS despite it not starting in neutral and I cycled through all the gears multiple times, wiggling the shifter a bit etc as you would and it didn't seem to do anything.

As much dirt as the Jeep has seen, I wouldn't be surprised if the NSS could use a good cleaning out or replacement but I wanted to some opinions as I'm working from home again and then plan to work on the Jeep when I finish work.

Would you lean towards it being the ignition switch, NSS or possibly something else I'm overlooking.

And just to get the obvious out of the way, it's a 95/4.0/AW4 - within the last year or so I have replaced the CPS (Mopar unit), full tune up, plugs/wires/coil/cap etc etc. Fuel pump/Filter are less than a year old (Bosch pump). I always use the best brands I can get for whatever I need to replace with the hopes that I won't have to replace that part again for a long time. Also within the last month I did the Jeep Cables Big 7 upgrade and all grounds/cables are tight and clean.

 

It could still be the NSS and there's a few ways to check. There's 2 plugs on the passengers side of your engine, one black and one grey that both run off down to the transmission.

You can:
Unplug the black one and join a wire from Pin 7 (Brown/Yellow) to Pin 6 (Black/Tan), this is on the vehicle loom side, not the transmission side.. Try starting it via the key and if it works every time, you have bad contacts in the NSS. If you can get the NSS off easily enough without breaking it, it's a matter of unscrew it's casing, clean up the contacts, clean out the old grease and re-grease with some dielectric grease.

Or:
Unplug the same connector and using a multimeter on the loom side

• Check for +12V on Pin 8 (Dark Blue/White) with the key in the RUN position
• Check for +12V on Pin 7 (Brown/Yellow) with the key in the START position
• Check continuity to ground on Pin 6 (Black/Tan)

On the transmission side:

• Check for continuity between pins:
  • 8 (Dark Blue/White) & 1 (Light Green/Black)
  • 8 (Dark Blue/White) & 2 (Grey/Black)
  • 8 (Dark Blue/White) & 4 (Brown/Light Green)

Let us know how it goes.

 

I'd be looking at ignition switch - But it would be worth doing some electrical diagnostic just to be sure.

It's weird that it started happening right when you added some tranny fluid. Is it possible that you jostled some wiring stuff when filling the ATF?? (Sorry, I have only ever dealt with manuals so I don't even know where the dipstick/fill tube is for the auto Jeeps.

 

Nah, it's just a funnel down the dipstick tube to add the trans fluid, didn't mess with anything at the time and when I was done it fired right back up like normal.

 

Thank you, I will do this when I get done working!

 

Is it getting 12V at the third (ignition terminal) on Starter when key is applied ?

Given it starts when you short those 3 terminals that will be a bad Starter Motor Solenoid

Had this twice, and even if you take the starter out, it will work with just 12V...but not in the vehicle

You can just replace the solenoid, or buy a used or new Starter​​​​​​​

 

The starter is literally a month old, I know new parts can fail too, but it's not a reman either. It's just the two terminals I have to jump, if I jump big to big the starter will just spin, if I jump big terminal to small terminal it will engage properly and the engine fires right up.

 

Okay, so I got done with work and tried jumping the pins etc and didn't have any luck. I don't have a whole lot of time tonight so I didn't get to dive into it too deep. I pulled the cover off the starter relay and a simple jump of the relay made it fire right up the same as arcing the starter. So at the very least, at least I can get it started and it drives fine/perfectly normal once it's running. I went ahead and ran to Advance and picked up a new Ignition switch, won't have time to install it tonight but I am also thinking I might go ahead and pull off the NSS tomorrow and give it a good cleaning inside as well but I don't think it's the NSS at this point, could be wrong but it's just my intuition I guess.

 

Good idea bypassing the relay, it shows that the supply side + starter are working fine so it's just the trigger side. From the relay slot you can determine which side of it is having troubles. One pin will be +12V with the key in START, the other will have continuity to ground when in PARK and NEUTRAL.

If there is no +12V, check Fuse 6 - 60A in the PDC under the hood. If that fuse is fine, it does point towards the ignition switch. If there's no continuity to ground, it would point towards the NSS, or you forgot to plug the black connector back together. However you choose to go about it, I hope you get it sorted.

 

So, I went back outside this morning to test a couple more things before replacing the ign. switch or pulling out the NSS to clean it. Just for giggles I naturally tried to fire it up before I did anything and it fired right up just like normal. Turned it on/off multiple times and it fired right up each time. Now I'm perplexed lol

 

One of the first common signs that there is a NSS issue is no back up lights. Or in my case with the trans in the 1-2 position it would shift out of 1st at 2k-2.5k rpms instead of ~4k.

 

I'm having starting issues too, I have a post awaiting approval from a moderator. But just to chime in, rather than actually tearing apart the NSS (as I did) to see if it works, since you already know which pins to jump to bypass it on the engine side, you can do a continuity check using a multimeter on the transmission side to make sure that you have continuity in Park and Reverse on those pins. And you can check all the other positions as well if you know which pins they are.

 

Happened to my 98. It was the solenoid on the starter. Toast. $26.00. The power from the ignition operates the solenoid coil which shorts the battery voltage through two contacts, through the motor and then to ground. You probably have voltage to the solenoid when you go to the crank position with the key but the contacts for the starter motor are not making.

 

I have had this on 2 XJ, and other vehicles...the main contacts within the solenoid that pass ~200A to the starter become burned and pitted, and will not pass enough current to turn the engine
You almost always get at least some warning signs

 

True, it does come with some prior tell-tale weakness but we don't know the OP's experience prior to total failure. And, it isn't wholly uncommon for a high-current contactor like the solenoid to just give up the ghost unannounced. In this case it's easy to check the ignition hot lead for voltage switching (with key operation) on the ignition terminal post of the solenoid. We know he has battery voltage. If there's ignition voltage sitting on the solenoid and it's operating (click), then the contacts are inop.