Hey -

I have a 1999 Cherokee(~174k miles) that currently won't start. For a little backstory, the Jeep sat for a little over a year due to the freeze plugs leaking - I fixed the freeze plugs then had an issue with the alternator (it seized up), it then sat for another 4-6 months (till now) and developed a no start issue. Last week I started working on her again and got her running (idling and moving in gear) by cleaning the 2 grounds on the fender near the PCM. I noticed before I cleaned the grounds that none of the gauges were working and that the ASD relay was clicking. After cleaning the grounds the clicking stopped and the gauges started working and she fired right up. I moved her to a better working location and parked her till today. I ordered a new alternator and belt and got them installed today and now the relay is clicking, gauges are not working and the Jeep won't start (cranks, but won't fire - fuel pump seems fine too). I cleaned the original grounds that fixed the issue, the ground on the fender next to the battery and the ground that is connected to the dipstick tube and none of that fixed the issue today. The battery seems to crank the Jeep fine, but I have it thrown on the charger this afternoon to make sure that it is 100% tomorrow. The only dashlight that is showing up is a flashing "brake" light when cranking - I believe it was doing this before I fixed it last week as well. I tried disconnecting the little wire on the alternator (the one held on with a nut) and still had the same issue. I also cleaned a little bit of gunk out of the other alternator connector as well.

Anyone have any ideas on what I can try next? I would have bet on it being a grounding issue considering that it worked last week. I did not start it up today before working on it, but all I did was put on a new belt and alternator.

Thanks-

Edit*
Forgot to note that I did try swapping the relays around as well - no change

 

If you clean up the grounds near the coil, you've done them all.

You will need to verify if you have spark, as well as fuel pressure (actually measure it). Have you checked for any codes?

I'd start with those and we can go from there.

 

I missed the grounds near the coil, but will get those cleaned today. My battery took a bit of charge but that didn't fix it this morning (didn't think it would, but had to try lol). I currently do not have spark when cranking, I was leaning towards a grounding issue due to that being what fixed it last week. I do not have any codes, but I will leave the battery hooked up today after cranking and crack out my code reader just to be 100%. I don't have a gauge to measure the fuel pressure, but I'll look at renting one from the part store or purchasing later this week if I don't get it fixed.

 

The fuel pressure is just to verify it's not the fuel delivery as well - if no spark AND no fuel than the diagnostic scenario changes somewhat. Do you hear the fuel pump prime when you turn the key to run (not start)?

Ok, so no spark- time to get the multimeter out and start going upstream to find where you have voltage again.

 

I went about cleaning the ground connections under the coil and ran into an issue. One of the nuts came off easily and looked fairly clean, while the second nut (the one that the negative battery cable runs to if it matters) was rusted on something fierce. I ended up breaking the eyelet on the small cable connected to this ground and went ahead and cut the end off of the negative battery cable due to the nut made onto the bolt starting to round off (I have a few spare battery cables at my dad's house from past projects and figured it would be easier replacing that than fighting with a rounded off bolt). After getting the bolt out of the block I was curious how rusted on the nut was and found out that it took pair of vice gripes and my 20v impact to get it off. I don't think that the rust made the ground connection there any better (lol), but I won't know for sure if that was the issue until I can find some sort of replacement bolt/setup for the rounded off bolt this weekend at Lowes or Ace.

Also , yes I can hear the fuel priming when I turn the key. It is, however, doing the same thing last week before I cleaned the grounds and seems to be running longer than it should (that is just about the only way I know how to word it)

 

The grounds at the coil are actually quite important. The ones near the PCM are not the PCM grounds
See pics (not mine)

 

Well, that is definitely interesting and makes me question why cleaning the grounds in the top pic fixed the issue originally

 

It didn't

 

So I think that I may have fixed the issue. After getting the new eyelet and negative battery cable on (in addition to replacing the short battery cable that ran from the battery to the side of the engine bay) the gauges all worked and she fired right up. Volt meter (in the jeep) showed 14 and it idled fine. I turned the jeep off and started it two more times, and on the second go about the the check engine light came on (codes below) and it decided that it didn't want to start back up after turning it off again.

The codes I got (and yes the code reader showed "N" and not a "P" (??)) are: N0101 Voltage Below Threshold and N0103 Maximum Historical Voltage Below Threshold. The jeep still cranked fine, but the battery was showing very low when I threw it on the battery charger. My thinking is that the issue, now, is that the battery is just junk and that it needs to be replaced. The battery is older, and has been sitting, but it charged up fine so I've been using it for this testing (I've also recharged after each time I messed with the jeep, I was fairly certain a new one was going to be needed whenever she is fully road worthy anywho). Does my logic seem fairly on point here? The only other battery I have available to me ATM is the one in my truck and its a side post that is nearly twice as wide, otherwise I would throw it in there and give it a try.

 

Hooked up the fully charged battery today and...nada... Gauge issue returned and she wouldn't start. No check end codes this time, just the same thing it had been doing and not starting. Tomorrow after work I'm going to dig out my multimeter and check the CPS sensor. From what I've read on this site you can check it for resistance (I believe? Will have to double check tomorrow) to see if its the issue. I had replaced the sensor a few years ago but it was with a cheap-o one from Amazon because I didn't have the money for the nice Mopar one. I've read the stories about the Mopar one being the only one that truly works

 

Here you go

https://www.cherokeeforum.com/f51/testing-cps-5563/

 

That can show a 19-2001 sensor is bad, but it won't prove it's good

 

Not everyone has an oscilloscope, mate..

 

I checked the CPS and it tested fine based on your above link, Roler.

I replaced the tie rod ends today and hooked the battery back up just for the heck of it to see what it would do and shockingly (not lol) it fired right up with no issues. The check engine light came on and showed 1 code, N0103. After shutting it off it would not start back up, but it did crank hard. I turned the key on and off a few different times and the fuel pump primed correctly and the gauges seem to be working, but it still would not start. I then tried revving the gas when cranking and it would, eventually, start (hard start) and idle fine after revving the motor for a few seconds. After the initial hard it seemed to idle fine and drive fine in gear (I only moved back and forth ~10-20 feet). If I just set there and crank it won't start at all but once I start feathering the gas it stumbles/hard starts and eventually gets going. Any idea on where to go from here?

 

Looping back on this with an update-

I think cleaning the grounds fixed the original issue with the current starting issue being the TPS. I've started and drove the Jeep the past couple of days and it has fired right up if you play with the throttle bit as its cranking. When you first start it you also have to throttle it a bit to keep it from dieing then it runs fine with the occasional RPM dip when idling. I'm leaning towards it being the TPS because I replaced the original one several years ago and have had somewhat similar issues on and off with the replacement ones (I've warrantied it 2-3 times now) from AutoZone. Since this part has lifetime warranty I'm just going to go ahead and warranty it this weekend and see if it fixes my issue next week.