Crank Position Sensor question
07-30-2011, 07:52 AM
#1
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Crank Position Sensor question
I suspect the CKP on my 2001 4.0 XJ Country is going bad - engine cuts out without any warning, but usually starts right up again. This item costs a ridiculous amount here, so before I go and replace it, I'd like to try that test where you measure the resistance between the B and C pins on the CKP connector. Being rather a dummy when it comes to this sort of thing, I wonder if anyone could help me with the following: 1) Is there any use in doing this test if the sensor is only intermittently faulty? and 2) I understand there should be infinite resistance between pins B and C - on my ohmmeter, this would be a reading of 1 (where 0 = no resistance) So any value less than 1 would indicate a fault? Is this correct? Thanks for any advice!
07-30-2011, 06:46 PM
#2
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Year: 1998 classic
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dont rely on testing it with a ohmeter, its bs. i tested a good and bad one and they both came back the same reading no matter how it was probed. the only real way to check it is to have it plugged into a sensor checker. all that thing does is magnify a pulse for the computer to read. its a magnet w wires. there are common symptoms that go with a bad cps but not too sure on all of them. Is there an autozone where you are?
07-30-2011, 07:07 PM
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Why couldn't u just order 1 online from anyone. The shipping to other countries is not that much for a 180 gram part. Also shop around- I have gotten many parts from Amazon with free shipping which were basically sent by the same company that I was originally gonna buy from.
You can also figure by the mikes on ur jeep and the year since its a part thats meant to fail eventually. Say u have 100K and its 10 years old u can easily replace it without fear of thinking u bought something u didn't need.
Things always seem to fail at the worst times so a little pre-maintenance is fine.
You can also figure by the mikes on ur jeep and the year since its a part thats meant to fail eventually. Say u have 100K and its 10 years old u can easily replace it without fear of thinking u bought something u didn't need.
Things always seem to fail at the worst times so a little pre-maintenance is fine.
07-31-2011, 05:30 AM
#5
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Testing with an ohmeter MAY, but also may NOT reveal the condition of the sensor.
One thing you could try before ordering one is this. Remove the connectors. There are 2 of them; 1 under the hood near the firewall/#6 injector and the one on the sensor itself. Get a can of electrical contact cleaner. Thoroughly spray each of the connectors, add a dab of dielectric grease and reconnect.
I have seen through the years a couple of situations where the sensor itself was okay, but there was debris and gunk inside of one of the connectors that created a resistance path, which made the sensor flaky.
Your sensor itself of course could be bad and it is a VERY common fail on the 4.0, just suggesting this as something you could try.
If you do end up ordering one, try to find an OEM JEEP sensor. There is no lack of threads of people having trouble with some (not all) aftermarket crank sensors. I buy plenty of aftermarket parts, but the crank sensor is one thing I buy ONLY from Jeep.
One thing you could try before ordering one is this. Remove the connectors. There are 2 of them; 1 under the hood near the firewall/#6 injector and the one on the sensor itself. Get a can of electrical contact cleaner. Thoroughly spray each of the connectors, add a dab of dielectric grease and reconnect.
I have seen through the years a couple of situations where the sensor itself was okay, but there was debris and gunk inside of one of the connectors that created a resistance path, which made the sensor flaky.
Your sensor itself of course could be bad and it is a VERY common fail on the 4.0, just suggesting this as something you could try.
If you do end up ordering one, try to find an OEM JEEP sensor. There is no lack of threads of people having trouble with some (not all) aftermarket crank sensors. I buy plenty of aftermarket parts, but the crank sensor is one thing I buy ONLY from Jeep.
07-31-2011, 06:05 AM
#7
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Jeep here have quoted me the equivalent of $220 for the part, so yes, I think you're right about ordering one online. Trouble is, things have a habit of disappearing into the black hole of our postal system!
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07-31-2011, 06:44 AM
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check your throttle sensor...with the crank sensor, most times the symptoms with that is you will be throwing a misfire code plus when it gets hot it from driving and you shut your jeep off and try to start it or just wont start until it cools off, it will sputter on start up, it will have trouble getting past 2000 rpms and then will stall
Last edited by tommyxj2000; 07-31-2011 at 09:36 AM.
07-31-2011, 08:22 AM
#9
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I suspect the CKP on my 2001 4.0 XJ Country is going bad - engine cuts out without any warning, but usually starts right up again. This item costs a ridiculous amount here, so before I go and replace it, I'd like to try that test where you measure the resistance between the B and C pins on the CKP connector. Being rather a dummy when it comes to this sort of thing, I wonder if anyone could help me with the following: 1) Is there any use in doing this test if the sensor is only intermittently faulty? and 2) I understand there should be infinite resistance between pins B and C - on my ohmmeter, this would be a reading of 1 (where 0 = no resistance) So any value less than 1 would indicate a fault? Is this correct? Thanks for any advice!
If it IS failing you'll have the 1391 code for it. The only time I have had a 1391 (intermitten) was when there was ONE pin on the inside (and I think it was A the far left one) was all corroded and nasty. Cleaning that out might have fixed it being intermitten... but I also had a spare CKP so I replaced it.
If you still have 1391 AND it's clean... check your distributor to make sure the bolt hasn't come lose. There's a bolt that holds the distributor, which has the CPS, in place. If it has come loose it will give the distrubor play, and that can also cause "intermitten CKP/CPS failure" because it's constantly fluctuating in position (and the PCM controls the spark timing so it's constantly trying to adjust to a dist. that is moving).
Now.. if the dist. is solid in place and the CPS looks clean (inside the connector AND the distribtor) and you DO have 1391.. that's when you know you need to replace the CKP. If you don't have that code, then don't worry about it. Until you get a code readout, don't buy ANYTHING. If you don't have 1391... I'm going to say judging by what your said it's your fuel pump. You exude the exact symptoms of a starting-to-die fuel pump. They usually don't just die on the spot. They slowly pump less efficiently.
The fact that when you crank it up and drive again hints to me fuel pump. When you restart a vehicle the fuel system is re-primed. If your pump is slowly starting to die this will get worse. Once for me it just outright died with no warning signs. Most people find that they slowly die (restarting always makes their "problem" go away).
There isn't a code for fuel pressure. The more you drive though, the more the fuel pressure is relieve from the fuel system as the fuel injectors release it. When the pump starts to die it can't keep up. When you shut it off and restart the fuel pump primes the fuel system (hence it goes back to the way it was when you started driving it, and problem goes away). The fuel pump just tries to keep the PSI at 49 +/- 1. The fuel injectors are releasing the pressure faster than the pump can keep up.
Here are some other links about the subject for your light reading. The first one fixed his problem and it was the fuel pump. The second one never responded with a fix (if you ever find a fix, do everyone a polite gesture and post it for someone else who has your problem down the road.. that's what this forum is for).
The last one is mine and it was also the fuel pump:
https://www.cherokeeforum.com/f2/wtf...r-speed-96940/
https://www.cherokeeforum.com/f2/ran...s-power-97499/
https://www.cherokeeforum.com/f2/buc...7/#post1119441
Last edited by CoffeeCommando; 07-31-2011 at 08:36 AM.
07-31-2011, 08:55 AM
#10
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Engine stalling out of the blue, but starting up again is a pretty common symptom of a failing crank sensor.............
And from my experience with them, they only set a check engine light or a code about 25% of the time.
And from my experience with them, they only set a check engine light or a code about 25% of the time.
07-31-2011, 09:35 AM
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This doesn't sound like CKP. CKP either works or doesn't 90% of the time. If it IS intermitten it probably just needs to be clean or your distributor needs to be checked for toothwear/loose bolt. It's a magnetic pickup that closes and allows voltage to run through it so definitely keep it from other magnetics.
If it IS failing you'll have the 1391 code for it. The only time I have had a 1391 (intermitten) was when there was ONE pin on the inside (and I think it was A the far left one) was all corroded and nasty. Cleaning that out might have fixed it being intermitten... but I also had a spare CKP so I replaced it.
If you still have 1391 AND it's clean... check your distributor to make sure the bolt hasn't come lose. There's a bolt that holds the distributor, which has the CPS, in place. If it has come loose it will give the distrubor play, and that can also cause "intermitten CKP/CPS failure" because it's constantly fluctuating in position (and the PCM controls the spark timing so it's constantly trying to adjust to a dist. that is moving).
Now.. if the dist. is solid in place and the CPS looks clean (inside the connector AND the distribtor) and you DO have 1391.. that's when you know you need to replace the CKP. If you don't have that code, then don't worry about it. Until you get a code readout, don't buy ANYTHING. If you don't have 1391... I'm going to say judging by what your said it's your fuel pump. You exude the exact symptoms of a starting-to-die fuel pump. They usually don't just die on the spot. They slowly pump less efficiently.
The fact that when you crank it up and drive again hints to me fuel pump. When you restart a vehicle the fuel system is re-primed. If your pump is slowly starting to die this will get worse. Once for me it just outright died with no warning signs. Most people find that they slowly die (restarting always makes their "problem" go away).
There isn't a code for fuel pressure. The more you drive though, the more the fuel pressure is relieve from the fuel system as the fuel injectors release it. When the pump starts to die it can't keep up. When you shut it off and restart the fuel pump primes the fuel system (hence it goes back to the way it was when you started driving it, and problem goes away). The fuel pump just tries to keep the PSI at 49 +/- 1. The fuel injectors are releasing the pressure faster than the pump can keep up.
Here are some other links about the subject for your light reading. The first one fixed his problem and it was the fuel pump. The second one never responded with a fix (if you ever find a fix, do everyone a polite gesture and post it for someone else who has your problem down the road.. that's what this forum is for).
The last one is mine and it was also the fuel pump:
https://www.cherokeeforum.com/f2/wtf...r-speed-96940/
https://www.cherokeeforum.com/f2/ran...s-power-97499/
https://www.cherokeeforum.com/f2/buc...7/#post1119441
If it IS failing you'll have the 1391 code for it. The only time I have had a 1391 (intermitten) was when there was ONE pin on the inside (and I think it was A the far left one) was all corroded and nasty. Cleaning that out might have fixed it being intermitten... but I also had a spare CKP so I replaced it.
If you still have 1391 AND it's clean... check your distributor to make sure the bolt hasn't come lose. There's a bolt that holds the distributor, which has the CPS, in place. If it has come loose it will give the distrubor play, and that can also cause "intermitten CKP/CPS failure" because it's constantly fluctuating in position (and the PCM controls the spark timing so it's constantly trying to adjust to a dist. that is moving).
Now.. if the dist. is solid in place and the CPS looks clean (inside the connector AND the distribtor) and you DO have 1391.. that's when you know you need to replace the CKP. If you don't have that code, then don't worry about it. Until you get a code readout, don't buy ANYTHING. If you don't have 1391... I'm going to say judging by what your said it's your fuel pump. You exude the exact symptoms of a starting-to-die fuel pump. They usually don't just die on the spot. They slowly pump less efficiently.
The fact that when you crank it up and drive again hints to me fuel pump. When you restart a vehicle the fuel system is re-primed. If your pump is slowly starting to die this will get worse. Once for me it just outright died with no warning signs. Most people find that they slowly die (restarting always makes their "problem" go away).
There isn't a code for fuel pressure. The more you drive though, the more the fuel pressure is relieve from the fuel system as the fuel injectors release it. When the pump starts to die it can't keep up. When you shut it off and restart the fuel pump primes the fuel system (hence it goes back to the way it was when you started driving it, and problem goes away). The fuel pump just tries to keep the PSI at 49 +/- 1. The fuel injectors are releasing the pressure faster than the pump can keep up.
Here are some other links about the subject for your light reading. The first one fixed his problem and it was the fuel pump. The second one never responded with a fix (if you ever find a fix, do everyone a polite gesture and post it for someone else who has your problem down the road.. that's what this forum is for).
The last one is mine and it was also the fuel pump:
https://www.cherokeeforum.com/f2/wtf...r-speed-96940/
https://www.cherokeeforum.com/f2/ran...s-power-97499/
https://www.cherokeeforum.com/f2/buc...7/#post1119441
07-31-2011, 09:41 AM
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random cyl misfire
cyl 1 & 3 misfire
or
cyl 3 & 5 misfire
not saying your wrong and im right or vise versa
07-31-2011, 02:36 PM
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I had a bad CKP that would fail intermittently when hot, no code thrown. It would usually happen when driving slow or coming to a stop it would just randomly die, then after it cooled down 10 minutes or so it would start back up. It would only happen every couple months. Other symptoms were that my gauges would go wacky when this happened, the fuel gauge would ping on empty and the battery gauge would jump around crazy. I took it to a shop but they couldn't confirm that it was bad. After researching the internet I replaced it on a hunch and have never had the problem again.
07-31-2011, 02:58 PM
#14
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I've had a CEL for it both times I've had to replace it. Maybe you drive a pre-96 and they don't CEL it, but I have a 98 and mine hasn't failed me yet.
07-31-2011, 03:03 PM
#15
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from my experience, it has always thrown codes and never stalled on me...would only give me trouble when driving long distance, take a 10 min break and then try starting up again
random cyl misfire
cyl 1 & 3 misfire
or
cyl 3 & 5 misfire
not saying your wrong and im right or vise versa
random cyl misfire
cyl 1 & 3 misfire
or
cyl 3 & 5 misfire
not saying your wrong and im right or vise versa
It's your coil packs. This is a common problem, as I have read many times on this forum, for the coil pack using XJ's to have problems starting and have misfires.
There was a TSB for it I have also heard. So the dealer should fix your problem for free assuming it hasn't been taken to a dealer already... and your PO took the heat shielding off.
Also, if you have a problem open a new thread. I almost thought this was the same original poster of this thread and got very confused. Anyone searching for something coil-pack related might be mislead by the title of the thread simply because (and that doesn't necessarily mean THIS thread) it doesn't list the title as anything related to a coil pack issue.