Sudden death - engine stops, but eventually restarts normally

I have a stock 93 XJ 4-litre 'Sport' with auto box, owned since new, not hard-used, has now done 130k miles.

Today after running for a couple of miles from cold, when turning a street corner, the engine suddenly died. Stopped instantly. No stutter, no warning. Nada. After a brief pause, I made a couple of attempts to start it. Nothing - not even a click.... though lights etc all suggested there was good battery power. Five minutes later, it started perfectly as soon as the key turned, and as if nothing had happened. The rest of the day, no problems.

Next time, will it cut out and die at 50 mph on the highway without warning?

I'm trying to approach this systematically. I'm assuming total sudden shutdown suggests some electrical or control issue, not dirty fuel, blocked filter or similar fuelling problem. So I have checked the obvious electrical things:

• battery is a good, new, Optima
• battery connections are good and tight
• charging circuit seems fine according to the gauge

Is it the NSS? It has been slightly 'out' for many years, and we're used to that. Usually starts first time from home, but if stopped within a mile or two, it sometimes won't restart in Park. Instant solution is to shift to Neutral, and it starts happily. Classic NSS problem, but we live with it. I did wonder if this was the cause, but I have just read in a forum search that the NSS can't/won't cause sudden shutdown while driving.

Is it the CPS, or some other gizmo, now intermittently misbehaving? I'm not enough of an engineer to run tests with meters etc, but is there anything I can check, spray, or tweak to verify?

One more possible clue. Very occasionally, like about once in 100 starts or once in a couple of months, it won't start and fire first time. I have to floor the pedal and keep cranking. After about 8-10 seconds, it catches, fires, and runs like normal. Then it doesn't happen again for months. Is this a pointer to something being not quite right? Or is it totally unrelated to the "sudden death" problem that has just shown up?

Intermittent problems are always the worst ones. But I am now very worried that the engine will cut out unexpectedly and totally in a situation (like at speed or overtaking on the highway) that could be dangerous or fatal.

I would guess Crank Sensor. When It dies wiggle Crank Sensor wiring and see if it starts back up.

Also Reccommend Cleaning IAC motor & T-body, but it sounds like more of a Crank Sensor Issue.

http://www.naxja.org/forum/showthread.php?t=1062496

this thread has tests for Cam and Crank Sensors. But sense its intermittent it will only test bad after it had died. That is for a H.O.

When this happens you need to see if you are getting spark. I've had this happen to me and it was the ignition coil oddly enough

10334226 said:

http://www.naxja.org/forum/showthread.php?t=1062496

this thread has tests for Cam and Crank Sensors. But since its intermittent it will only test bad after it had died. That is for a H.O.

Click to expand...

I looked carefully at that thread as Tim's advice on testing is fairly clear. The test of the CPS connector is different for the 1987-90 engines and the 1991 onwards. My Jeep is a 93 model (build date Dec 1992). I don't know whether it has the H.O. engine or not...

So as a first step I tested the CPS connector with a digital ohmmeter. According to Tim's advice, an ohmmeter across B - C should show open loop. Here's what I got:

A - B open loop
A - C open loop
B - C reading of 16.07 (milli-ohms?)

So is my CPS shot?

For what it's worth I have not noticed any odd behaviour on the gauges in the dash, and the Check Engine Light is coming on as normal with the ignition (and going out when the engine runs).

Wonder if its a failing fuel pump? Would be a unique failure though...

Hi,
I had the same problems with my 93 XJ, sometimes it would take 15 minutes before it would restart. I had a new CPS fitted about 3 years ago and have had no problems since. I would say that for the few dollars cost fitting a new CPS is good insurance, it might fail out in the middle of death valley next time and it might not restart. Your call.

Thanks for comments....

But before I go looking for a new CPS, and tackling the task of removing and replacing it (which is a bit awkward as it's hard to reach), I really would like to know if the ohmmeter test I did and the figures quoted in my earlier post show a fault or not?

I'm not an auto-electrics engineer, but just trying to figure things out. If the CPS is good, do all three readings show "open loop"? And if the CPS is failing, or not working, does the ohmmeter reading vary depending on whether you test it in "normal" (working) conditions or when the engine has just stalled?

Do I have to carry a meter around all the time and then leap out and take a reading next time the engine dies?

When you say "nothing", you mean it doesn't turn over or it just turns and doesn't start? Everyone seems pretty sure about your cranksensor, but I've had similar problem with the sensor in the distributor!

Now I have to admit my motor is no 4.0L but I believe they have a distributor and not a bunch of coils? If so add this to the checklist. As far as your reading goes, I don't know if specs are available best bet might be to get someone to test his!


PS. my truck just died on the highway, 50mph... no spark.

Just to clarify - for foress_89 and any other readers. So far, the Jeep engine has only died on me once while driving along, and that was at 5mph on a street corner. So it's not as if I have had lots of opportunities to see exactly what all the symptoms are.

But this much is clear. After it had "died" and the vehicle stopped, I tried twice to start it. Ignition lights etc on dash showed as normal. but engine absolutely would not start. No crank, no turnover, no noise from starter motor, not even a click. Exactly the same behaviour as when the NSS prevents starting.

On the second attempt to start, I checked there was battery-power by switching on the interior light. Then tried to start. Light did not flicker or dim - which to me means the starter was not asking to draw current from the battery. Reinforces the idea that something is actually preventing the ignition circuit from completing and the engine from firing.

After some 10-15 minutes, I tried again: engine started and fired perfectly as normal, no excessive cranking, no struggle.

Problem now is, I can't re-create the situation. I can't make it "die" or stall while running. That's why I really would like to know whether the basic test I have done of the CPS connector with the ohmmeter reveals anything.

i had a problem like this , it turned out to be one of the main power wires in the bulkhead connector . it had corroded away and was making contact most of the time , and on occasion it would kill the motor . get someone to shake the wires at the bulkhead while your crank the motor , see if that can re-create the issue . its a simple solder fix

waggy said:

i had a problem like this , it turned out to be one of the main power wires in the bulkhead connector . it had corroded away and was making contact most of the time , and on occasion it would kill the motor . get someone to shake the wires at the bulkhead while your crank the motor , see if that can re-create the issue . its a simple solder fix

Click to expand...

I agree, now that you explained the problem like that, it sounds like a bad connection at some place. I do not believe the crank sensor would prevent the motor from turning, would it? It could be something in the ignition switch, or one of the starter solenoids, or just bad wiring in between.

foress_89 said:

I do not believe the crank sensor would prevent the motor from turning, would it?

Click to expand...

Hey - if that is true, then it is interesting - especially as other posts say that a failing CPS (especially if it is thermal failure) will cut the engine dead.

I'm beginning to get confused.

To go back to the earlier question, what should the ohmmeter readings be between each pair of the three pins on the CPS connector?

I will be honest with you this test does not look very promising. Not that your results would be bad, it's just not a very good test. Some parts you have no choice but to try a new one. (or a used one!). But your sensor will obviously give a good reading since the truck starts! Right? It only failed once. In other words, you can spend the money on a new cranksensor, and end up stalling again tomorrow afternoon, if it wasn't the problem.

I would like very much too be corrected if I'm wrong, but I'm actually pretty close to 100% sure the CPS will NOT keep the engine from turning (from starting, but not from turning). It might as weel have been your safety neutral switch like you said! Or virtually anything. If you cannot make the problem happen again, it will be very hard to fix. But you know that already.

The problem you stated in your first post (wouldn't start well every other month or w/e), is probably unrelated, since the motor would not crank this time.

I'm just trying to help you out! :cheers:

Thanks foress_89 - I appreciate your help... hope I didn't appear ungrateful!

The intermittent problems are always the hardest to pin down. But as parts are so hard to find over here, and very expensive if available, I don't have the option of changing-out a variety of parts just to see what makes a difference.

A simple no-start is a problem but not usually life-threatening. Most times it happens on the driveway or in a car park. You're stopped, and you're safe; although of course it's an inconvenience. So I would not be so anxious if it was just a matter of not-starting, or lots of cranking before the engine fires.

What worries me on this problem is that something - and I'm still not sure what - cut the engine dead with no warning while driving along. Lucky me: I simply stopped in a suburban side street. But what happens if next time the engine suddenly cuts while I'm in the middle of overtaking another car on a two-way road? Especially if there's another car heading towards me...

That's why I need to nail down pretty quickly, and precisely, what might have caused the engine suddenly to die last week, not ten minutes after starting up, and while driving normally along a road.

I have seen on another thread that a faulty NSS will prevent the engine starting, but once the engine is running the NSS can't shut it down. Clearly the evidence so far is that it isn't a fuel blockage or fuel pump failure (for this would make it unlikely that the engine would restart normally after 10 mins). I have checked the obvious battery-related connections, and all are sound. Which rather leads to the conclusion that something "told" the engine to shut down, or cut the flow of information or power that kept the engine running.

That's as far as logic and detective work have taken me. I feel I need to know what else to test, and how...

One troubleshooting tidbit I can give you for my earlier post is to remove the coil(a real PITA on the HO models) and visually inspect the case for cracks. I have had one coil fail on my 96 that was cracked. I have seen one other HO coil fail on the trail and it was cracked. I carry a spare on the trail rig now.

It seems heat is its enemy and once it cracks then it becomes a snowball of issues. My 96 for instance would run for hours on the highway with no issue but crawling along on the trail would cause it to stall. Waiting 10-15min would let it restart.

I have seen a CPS that would do the same, it was also on my trail rig. I poured cold water over it and the rig fired right up. I replaced the faulty CPS and all is good(I also carry a spare CPS on the trail:idea

xjtrailrider said:

(I also carry a spare CPS on the trail:idea

Click to expand...

you should tow an extra jeep


Jokes aside, just be careful with the truck. At some point it will happen again and you will be able to troubleshoot. You could sell it while it works.

br1anstorm said:

I have a stock 93 XJ 4-litre 'Sport' with auto box, owned since new, not hard-used, has now done 130k miles.

Today after running for a couple of miles from cold, when turning a street corner, the engine suddenly died. Stopped instantly. No stutter, no warning. Nada. After a brief pause, I made a couple of attempts to start it. Nothing - not even a click.... though lights etc all suggested there was good battery power. Five minutes later, it started perfectly as soon as the key turned, and as if nothing had happened. The rest of the day, no problems.

Next time, will it cut out and die at 50 mph on the highway without warning?

I'm trying to approach this systematically. I'm assuming total sudden shutdown suggests some electrical or control issue, not dirty fuel, blocked filter or similar fuelling problem. So I have checked the obvious electrical things:

• battery is a good, new, Optima
• battery connections are good and tight
• charging circuit seems fine according to the gauge

Is it the NSS? It has been slightly 'out' for many years, and we're used to that. Usually starts first time from home, but if stopped within a mile or two, it sometimes won't restart in Park. Instant solution is to shift to Neutral, and it starts happily. Classic NSS problem, but we live with it. I did wonder if this was the cause, but I have just read in a forum search that the NSS can't/won't cause sudden shutdown while driving.

Is it the CPS, or some other gizmo, now intermittently misbehaving? I'm not enough of an engineer to run tests with meters etc, but is there anything I can check, spray, or tweak to verify?

One more possible clue. Very occasionally, like about once in 100 starts or once in a couple of months, it won't start and fire first time. I have to floor the pedal and keep cranking. After about 8-10 seconds, it catches, fires, and runs like normal. Then it doesn't happen again for months. Is this a pointer to something being not quite right? Or is it totally unrelated to the "sudden death" problem that has just shown up?

Intermittent problems are always the worst ones. But I am now very worried that the engine will cut out unexpectedly and totally in a situation (like at speed or overtaking on the highway) that could be dangerous or fatal.

Click to expand...

OK guys, there is no sensor that will keep it from cranking. The neutral safety switch if you have a auto will do that. There are only a few things that will keep the starter from cranking if the power is still there to run the headlights. I usually use the horn instead of lights to test since it pulls a fair amount of current and I can do it by myself.

So the most likely culprets are:
1. neutral safety switch
2. Solenoid by battery that uses the NSS input to control power to starter
3. Bad ignition switch

Given those, which can shut down an engine? Only the ignition switch.

Like one person said, a corroded/broken wire at the bulkhead or somewhere in the circuit is also a possiblility.

OK, so when the motor dies on you and yoy coast to a stop.

Then you turn the key to restart it and the starter doesnt make a sound?

Is it like your not even turning the key to start position, but there is still power to the dash gauges and lights?


If that's the case then it will be the Ignition Switch up under the dash on top of the steering column.

There is a long rod that goes from the key cylinder down to the switch that moves the switch from accy-off-run-start.

If you feel the top of column while turning key back and forth you can feel the rod moving.:eyes: