mtnance

96 Jeep Cherokee Sport 4.0 4x4 auto

Had problems with random shutdown while driving and random no starts (no turnover). In all my two days worth of reading and checking with a shop, here's what I think to be an answer. The NSS is bad or going bad.

Been told to check the Throttle Position Sensor and the Crank Position Sensor - Mechanic told me these would not cause the engine not to turn over, it just won't start. Starter Solenoid bad - told that once engine is running, won't cause it to shut down. Starter Relay - told to feel for click and swap with known good relay, it's all good. Fuel pump/pressure bad - it checks out okay. Coil -again told that engine would turn over but won't start.

All that I think it left is the ignition switch, but was told it's not that common to go bad however it still possible.

Once last week, I noticed the reverse lights did not come on when wife backed down driveway,...but it did start....haven't noticed or realized that problem since.

Question: would a bad (or going bad) NSS cause an engine shutdown while doing 40mph down the road?

Happened three times within 15 minutes. Was able to crank back twice but the final time, wouldn't start back,...used screwdriver to short starter to fire up and get the last 1/4 mile home.

I am missing something?

Has anyone rebuilt it? I found a link to do so,...but don't want to tackle this until I learn it can or cannot cause a shutdown. Link: http://jeep-xj.info/HowtoNSSrebuild.htm

kjc

Question: would a bad (or going bad) NSS cause an engine shutdown while doing 40mph down the road?
No.. it would only cause a 'no start' condition.
If it's bad, it can prevent starting with the key, but so could the ignition switch. Since you 'jumped' it at the starter, you bypassed both parts.
It sounds like you might have 2 separate issues. From reading similar issues, you could need a CPS.(for the random shutdown issue) They can be tested before you replace 'em. I'd start with that myself. As for the key not starting, if it doesn't spin the engine, i'd suspect the ignition switch. Good luck

xjsnake

^This^

If you don't have reverse lights you need to clean your NSS anyway so you might as well go ahead and do it. The hardest part by far is getting the old unit off in one piece.

If for some reason it breaks while taking it off (fairly easy to do) you can get one much cheaper than the dealer or regular autoparts stores. I got mine at carpartswholesale.com I was worried about it being cheap junk but so far I've had zero problems with mine.

mtnance

Here is the latest:

This morning, I start the Jeep fine place my finger on the fuel relay and the starter relay. It shut down in 30 seconds and the fuel relay clicked once. Swapped the relays and I started the Jeep again,...same thing, fuel relay clicked once.

CPS? How do you test it? I'm a fair mechanic but not much in electrical
Fuel Pump?

Just found: Trouble code P0351 means: Ignition Coil 1 Primary Circuit Malfunction

Was probably an old code, no check engine light on and the car starts fine. In fact, now that it's been 1.5 hours since tinkering,...it has stalled once ata idle in the driveway....now it seems to run fine. Has idled for 5 minutes or so. Starts up fine

So whatever it is, is intermitant

kjc

"CPS? How do you test it? I'm a fair mechanic but not much in electrical Fuel Pump?
Sorry, CPS is crankshaft position sensor. Search this forum for cps testing.. I'm pretty sure I saw the proceedure on here.

Just found: Trouble code P0351 means: Ignition Coil 1 Primary Circuit Malfunction
Well that's new The coil can also be tested.. since your problem seems intermittant, the coil could be on its' way out. I'd check that first, just cause it's more accessible.

mtnance

Just an update:

Replaced the Crankshaft Position Sensor and the Throttle Position Sensor and the Camshaft Position Sensor.

Engine turns over now, but there's no spark from the coil. Tested by pulling the coil spark plug and holding it close to distributor cap to look for spark while being cranked.

Seems strange that before I changed the sensor(s), I had spark,..engine just would not stay running.

I guess I'll get a new coil tomorrow,...but could this be something else? Something I've done?