Duckman570

Here we go. Started my jeep yesterday after not driving for about 90 days. Started right up. Came to temp. Just about to close the hood and engine shut off like it had been shut off with the key. Went to restart and the starter turns the engine fine but won't start. Starting sounds different then it ever has. Doesn't even sound like it wants to start. Jeep had run flawlessly for the last 13 years. Anyone have a similar situation? Place to start looking.

pdowty68

I need more info, you got spark? Did it shut off quickly, or sputter and die?

pdowty68

NEVER let anyone tell you the 4.0 isn't a good engine! Yesterday my uncle tried to tell me the 3.6 v6 form the minivans is a better engine! 4.0lho forever! Sorry, I defend my xj and jeep very strongly... Just a thought I had to put out there

Kong1965

Is it throwing a CEL?

Does it have gas in it (don't get pissed, I've spent days working on a starting issue, only to find out the gas gauge wasn't working and adding a gallon solved the whole MFer)

Number two, and you'll see this everywhere in the threads, remove, clean and reattach every single ground point on the vehicle. Jeeps are notorious for this failure.

How old is the battery? Won't throw CEL, and has caused more than one starting problem. Don't give a **** if it cranks, a bad battery will keep it from starting and running.

From there it can be multiple things.

Cam Position Sensor.
Crank Position Sensor.

Fuel pump, but don't go there until everything else is eliminated. Why? Cost and effort, trust me.

Start with the basics and go from there.

Never had a problem I couldn't fix with one. And yes, the 4.0 will run well over 200k, but sensors and electrical behaviors will give you fits. No doubt.

Kong

Duckman570

The engine just died like the key had been shut off. Thought about a faulty fuel gauge. Haven't really wrenched on much in the last ten years but I'm capable . The crank sensor has never been changed. The battery is weak but new 90 days ago. Not sure about fuel or spark. Has coils on a rail .where do I check for spark on the coil packs,and how about fuel where would I check to verify fuel

BlueRidgeMark

That's not likely a fuel problem, then. But check it anyway!


Testing time!


Charge it before you do anything else. Basics, basics, basics!

Get an El Cheapo spark tester at your local parts store. You disconnect the plug, and put the tester in between the plug and the coil. NOTE: I haven't worked with the coil packs, so I don't know if you have room for this. Someone else will chime in, I'm sure.


Simple test, bang on the bottom of the tank and see if it sounds hollow. Don't laugh. I spent hours wrenching on a car one time, pulling my hair out. My buddy who doesn't do any wrenching stopped by, watched me for a bit, and asked if I had checked the gas.

Problem solved.

And I couldn't even blame a faulty gauge! I hadn't even thought of it!

Basics basics basics!




A better way is to rent a fuel pressure gauge from the parts store. Autozone (and Advance?? Maybe?) will "sell" you a tool at full retail. Use it, take it back, and get a full refund. Not a bad deal!

tjwalker

I agree that you need a strong battery going into this repair. If you have marginal available voltage, you can dig yourself a hole pretty quickly as the engine management system needs a certain amount of available voltage to work properly; we're not just talking about the ability to crank the engine here. Fully charge you battery overnight; it takes a long while to charge a battery. If you don't have a charger, buy one. Everybody should have a battery charger. If it still is struggling to crank the engine after charging, have it "load tested" at the parts store you bought this battery from. It is not that unusual to have premature fail of a newer battery.

You need to determine if you are missing fuel or spark. As the 00-01 have the coil rail ignition system, checking spark isn't as easier as earlier model XJs.

I'd try a simple shot of gas into the intake. If the engine starts and runs for a few seconds, you have identified a fuel delivery problem. This also serves the purpose of a "quick and dirty" test on if you have spark as if you have good spark, the engine should fire with gas introduced. This is the first thing you should try after you have a strong battery!

Below is information on testing spark and also on the "route of spark" on the 91-01 XJ. If you are missing spark, the crankshaft position sensor is absolutely the #1 suspect. If you replace this, do yourself a huge favor and buy a MOPAR unit directly from Jeep. Aftermarket crank sensors are very "hit and miss" with a lot of miss. To be fair, some will work, but your #1 bet for reliability and longevity is a MOPAR crank sensor.

Good luck and be sure to keep us updated as we are all learning here....
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The coil design for the 00-01 is significantly different than that of the single coil and distributor setup on the earlier 4.0. You basically have three coils firing 6 plugs in the correct sequence, every crankshaft rotation (waste spark design). This is an engineering departure from the older, single spark every other crankshaft rotation.

You can test the coil pack like you would the old single coil design, but its more technically involved than physically accessing the spark plug end. Because of the design of the coil rail, don’t test the coil rail one spark plug port at a time. Testing one port at a time causes the remaining coil ports to be free floating (ie, not properly grounded through the spark plug). Free floating an encapsulated coil secondary causes significant increases in the voltage induced in the secondary. This increased voltage can easily exceed the dielectric breakdown of the coil secondary and could cause the coil windings to arc internally and break down the insulation. If this happens, it has the effect of reducing coil energy delivery potential in the best cases and in the worst cases, causes the coil to fail. You need to install all 6 spark plugs to ensure you won’t damage the coil rail.

Because it is difficult to guarantee that you can correctly ground all 6 plugs at once, you should make up 6 separate jumper wires about 2 feet long. Pull the rail and flip it upside down. Insert 6 sparkplugs into the rail. Attach one end of a jumper wire to the threaded part of the sparkplug with a large mouth alligator clip and attach the other end of the jumper wire to engine ground. Once all 6 are hooked up this way, you can then perform your engine cranking test while observing spark on all 6 plugs.
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Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.

Duckman570

Wow, thanks for all the great information. I will be charging up the battery overnight. And will let you know what I find. Thanks again everyone for all the help!

KD4315

I'm not comfortable admitting how many times I've done this exact same thing.

bamarider

I just went thru this same issue. Jeep was running fine, stopped @ a tire store to check on some tires. When I went to leave it started for a few seconds then shut off, and wouldn't re-start. I let a repair shop located in the same building check it out. They replaced cps & ignition coil. Got the jeep home, the next morning same problem. Jeep was in need of a complete tune-up, so I replace cap, rotor, plugs & wires and the ignition module. From info I got from this site I check & clean all grounds & electrical connection. After doing all of that it failed to start most of the time and I never get a CEL. I rented a code scanner from autozone and there's no codes. After several tries to start the engine with the scanner plugged in it fails to communicate with PCM. So after all that it turned out to be a faulty PCM. Ordered a reman. unit from auto computer exchange & jeep has been running great since. So after verifying everything else ok, don't rule out the PCM.

BlueRidgeMark

I suspect if we started a club we could have lots of members.

Duckman570

On my way to parts store to buy a battery and battery charger! It appears someone needed mine more than me. When I went outside this morning both were gone! Unbelievable!!!!

pdowty68

I guess someone wanted your battery, but now you get a new one