No start.........crank position sensor?
01-22-2014, 05:25 AM
#1
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Year: 1990
Model: Cherokee
Engine: 4.0
No start.........crank position sensor?
Here's what happened............
I went to a gas station (I've been using this same gas station for years so, I doubt it is the problem) to add enough gas to get me through the week. The XJ still had about 1/4 tank and I added about 7 gallons to that. On the way home, I stopped at a store to get a few things. When I got ready to drive home, that's when it started acting up.
Cranking time was far longer than usual, then it would fire off and die immediately. It did this about 5 times before it finally stayed running. The drive home was fine........the engine ran fine with no hiccups.
The next morning however, it would not start. The battery is nice and strong and it turns over just fine but, won't fire off.
I work with 3 mechanics that have worked for or with Jeeps in the past and all 3 suggested the crank position sensor. Anything else it could be?
I went to a gas station (I've been using this same gas station for years so, I doubt it is the problem) to add enough gas to get me through the week. The XJ still had about 1/4 tank and I added about 7 gallons to that. On the way home, I stopped at a store to get a few things. When I got ready to drive home, that's when it started acting up.
Cranking time was far longer than usual, then it would fire off and die immediately. It did this about 5 times before it finally stayed running. The drive home was fine........the engine ran fine with no hiccups.
The next morning however, it would not start. The battery is nice and strong and it turns over just fine but, won't fire off.
I work with 3 mechanics that have worked for or with Jeeps in the past and all 3 suggested the crank position sensor. Anything else it could be?
01-22-2014, 05:34 AM
#2
CF Veteran
Yes, of course it can be something else! But the CPS is high on the list.
Get a quality (dealer) one, to increase your success...aftermarkets are unreliable.
Some other causes can be poor battery, CAM sensor, fuel delivery issues
Keep in mind: no starts are usually due to either, no spark, no fuel, no both, no como bustion...so to answer your question: in all of these areas could be a possible cause...however, I'd say: change out your CPS
Get a quality (dealer) one, to increase your success...aftermarkets are unreliable.
Some other causes can be poor battery, CAM sensor, fuel delivery issues
Keep in mind: no starts are usually due to either, no spark, no fuel, no both, no como bustion...so to answer your question: in all of these areas could be a possible cause...however, I'd say: change out your CPS
01-22-2014, 06:39 AM
#3
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
How about TESTING the CPS?
Takes about 30 seconds to do:
Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Revised 01-26-2013
Takes about 30 seconds to do:
Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Revised 01-26-2013
01-22-2014, 07:05 AM
#5
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01-22-2014, 07:07 AM
#6
CF Veteran
Renix....I'll leave this to you then 
....but in the post updates, I think the testing becomes more unreliable.
....but in the post updates, I think the testing becomes more unreliable.
01-22-2014, 07:09 AM
#7
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01-22-2014, 07:12 AM
#9
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Year: 1990
Model: Cherokee (XJ)
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Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Revised 01-26-2013
01-22-2014, 06:20 PM
#11
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01-24-2014, 05:11 AM
#14
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Ok, so I finally finished fixing my step parents Dakota and was able to run some tests on the XJ last night. Fuel pressure is good, and it has good spark. I did both the ohm and voltage tests on the CKP just to satisfy my curiosity. The ohm reading was 210 which is well within the range shown in alldata. The voltage however, came up short at .35 vac so, I guess I'll be calling the Jeep stealership down the road and buying (or most likely ordering) a crank position sensor. I'll be pleasantly shocked if they actually have one in stock.
The part I'm REALLY not looking forward to, is replacing it. It's in a crappy location that's going to involve a LONG extension and swivel socket just to get to and I can only imagine how much of a PITA it's going to be to install the new one.
Hell, (because it's 11 degrees outside) it's almost worth it to have it towed in to work and pay our shop to replace it. I'd only pay half the labor which would be about $28.00 and because our tow service driver is a friend of my step dads, I could probably get it towed for about $20.00.
The part I'm REALLY not looking forward to, is replacing it. It's in a crappy location that's going to involve a LONG extension and swivel socket just to get to and I can only imagine how much of a PITA it's going to be to install the new one.
Hell, (because it's 11 degrees outside) it's almost worth it to have it towed in to work and pay our shop to replace it. I'd only pay half the labor which would be about $28.00 and because our tow service driver is a friend of my step dads, I could probably get it towed for about $20.00.
Last edited by Hamster; 01-24-2014 at 05:26 AM.