Stalled and wouldn't start, now starts

This morning on my way to work my jeep died on the road. I kind of went on and off a few times and then died entirely. The tach dropped to zero for a few seconds and then the engine kick back in. Obviously the last time it didn't. I tried starting it and it was like it had no gas. Being in traffic, I just had it flat bedded to the nearest shop and went to work. Now they have it and can't get it to not start. I hate having other people work on my stuff. Anyway, any input would be appreciated.

Sounds like an electrical issue for sure - year/engine/transmission/other relevant specs?

Shot in the dark, check your ASD relay, fuses, make sure all the connections are tight ESPECIALLY ones on the battery, alternator, and PCM. Also unplug and reconnect the CPS a few times.

1998 4.0, automatic transmission.

My NSS throws a 705 code if I leave it sitting too long. This happened recently. Is that relavent?

Sounds very typical for a crankshaft position sensor (CPS)

old_man said:

Sounds very typical for a crankshaft position sensor (CPS)

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X2 especially if the tach quit working

CPS it is. Thanks for the input everyone.

yep, usually a CPS that is going out will start to fail when it gets warm. When you let it cool down or pour water on it, if it starts back up fine, then its a sign that CPS needs to be replaced asap before it completely goes out. Had the exact same problem.

Yeah, too bad I was on my way to work when it happened. I don't know why we insist on keeping these things going, but clearly I'm not alone. XJ's forever, my other one made it to 200k.

Sounds like a great reason to bail out of work for the day! :eyes:

It's not just XJs that do this actually, a friend of mine who drives an altima reports that the cam position sensors on those die with astonishing rapidity also, and are similarly located between the back of the engine and the firewall. Really beats me why the darn engineers can't think ahead and put all the fiddly delicate sensors on the FRONT end of the shafts instead of the back...

i'm a mechanical engineer, and I question these things continuosly. Were they not paying attention in school?

The creative minds draw it on paper, then mold it out of clay, and then management tells the engineers to make it all fit--that is why things don't make any sense.

As an electrical engineer I can somewhat attest to joe_peters' comment... they ask us to make it all fit, and then to make it all fit in the budget. And then for good measure they ask a factory in China for their lowest possible bid on the sensors so some profit fits in the budget too.

joe_peters said:

The creative minds draw it on paper, then mold it out of clay, and then management tells the engineers to make it all fit--that is why things don't make any sense.

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I know, I hate to say it but the engineers get screwed in the end. Managment already knows what they want. They don't care about logistics.

The 705 code may be able to be resolved by cleaning/regreasing your NSS. I'd try that before purchasing a new one as they can be kind of spendy. There is another current thread on this forum titled "neutral safety switch" which contains a link from Joe on how to perform this procedure.

Your no-start could be a few things but the #1 suspect is the crank sensor. If you have it at a shop, a good technician will generally figure this out pronto, but here's more information on it.

Crankshaft Position Sensor: (CPS/CKP) Failure Symptoms / Testing

*Both the fuel gauge and or voltage gauge may not work/display

*It is possible that you may see a No Bus on the odometer (on newer models only)

*You will have no spark. Fuel pressure may check out okay at the fuel rail, but fuel won’t get to the fuel injectors

*For 96 + newer, sometimes the OBDII code reader has trouble connecting to /reading codes. Crankshaft position sensor failure may or may not result in a check engine light/fault code.

*Crankshaft position sensors can be intermittent resulting in an abrupt misfire. "Thermal failure" is common. Thermal fail means that the sensor fails when engine gets hot, but works again when engine cools down. Be aware of this when testing, as if you have a sensor that suffers from thermal failure, it’s possible that it may test GOOD as soon as it cools down.

*Don’t get tunnel vision and assume the sensor is bad (unless it checks out as bad with a meter) Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Check/clean/repair as necessary.
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CRANKSHAFT SENSOR TESTING PROCEDURE: 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.

2. Place an ohmmeter across terminals B and C. The terminals are identified as A-B-C looking into connector from left to right with the "notch" in the middle of the connector on your right. Ohmmeter should be set to 1K-to-10K scale for this test.

3. The meter reading should be open (infinite resistance). Replace sensor if LOW RESISTANCE

im having a similar situation but...

i parked my truck and couldnt figure out the issue so i assumed it was my NSS.....trying to remove it now but its seized on good.

could the crank sensor cause the truck to stall out when it goes into gear?

DaveVmax said:

im having a similar situation but...

i parked my truck and couldnt figure out the issue so i assumed it was my NSS.....trying to remove it now but its seized on good.

could the crank sensor cause the truck to stall out when it goes into gear?

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If the CPS/CKP harness has become fried or shredded, and when you put it in gear it contacts metal, then yes. How about a cracked bell housing, when you put it in gear torque is applied and the CPS/CKP moves too far from the flexplate/flywheel, that would kill the engine. Wouldn't even have to be busted, maybe the bell housing to engine mounting bolts are loose. Maybe the CPS/CKP mounting bolts are loose.

What is the condition of your electrical system? Got fuel pressure?

all my electrical is good...no shorts or bad grounds.

got fuel pressure and the pump works. I just had a look at my CPS and the wires look good but the sensor looks a little dirty with grime.

DaveVmax said:

all my electrical is good...no shorts or bad grounds.

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Not likely.

When it stalls, check for spark.

my coil is good, new wires, new cap and rotor, new plugs

it has spark.

If it has spark, then the problem is not the crank sensor. How did you test for spark? It needs a strong, blue, snapping spark to fire the engine. Orange spark indicates a weak spark which isn't good.

If you do have good spark, then you have a fuel delivery problem.

You said you took it to a shop. What did they find?