Could mud be fouling my CPS
06-12-2012, 07:09 PM
#1
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Could mud be fouling my CPS
I know I'm getting low volts from my '87 jeeps CPS and have no spark. Any chance mud could be fouling it
06-12-2012, 07:25 PM
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You don't need mud to foul it. The crank sensor is a common fail for any 4.0 engine.
Test it. Here's how.
-----------------------------------------------------
Renix (87-90) Crankshaft Position Sensor 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 3.5 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 crank sensor directly from the Jeep dealer for best reliability and longevity.
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 it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Test it. Here's how.
-----------------------------------------------------
Renix (87-90) Crankshaft Position Sensor 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 3.5 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 crank sensor directly from the Jeep dealer for best reliability and longevity.
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 it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
06-12-2012, 07:29 PM
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Yeah, my bad. I didn't meantion its a common issue that its bad. I, for some reason, was thinkong you wanted to hose it off and make it work again, neglected to mention that it is a common issue.
06-12-2012, 07:41 PM
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Waiting for an update.
If crank sensor checks out okay, then move onto testing the ignition coil and having the ignition control module (under coil) tested. The ICM can't be tested with a meter.
06-12-2012, 08:20 PM
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Originally Posted by TheJerm
CPS uses magnetics so unless the mud is made out of iron and your bellhousing is full of it, i highly doubt it
I get .2 volts and have back up coil brain and dizzy that don't change anything
Just wish full thinking and laziness
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06-13-2012, 12:46 AM
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06-23-2012, 04:08 PM
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Will someone please reach through the web and slap me for being so stupid got a few extra $ and wanted that instant gratification can't wait for jeep sooooooooo 3 CPS later still no volts the old one gave me .3 now less than .1 might try one more in the morning but even if it starts I'll be ordering one from jeep
Got em at autozone should have tried the JY might have found one that worked
Got em at autozone should have tried the JY might have found one that worked
Last edited by Rustydog555; 06-23-2012 at 04:12 PM.
06-23-2012, 04:33 PM
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Originally Posted by Rustydog555
Will someone please reach through the web and slap me for being so stupid got a few extra $ and wanted that instant gratification can't wait for jeep sooooooooo 3 CPS later still no volts the old one gave me .3 now less than .1 might try one more in the morning but even if it starts I'll be ordering one from jeep
Got em at autozone should have tried the JY might have found one that worked
Got em at autozone should have tried the JY might have found one that worked
06-23-2012, 04:45 PM
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Originally Posted by Johnthepanpire
I know the new fuel pump I put on is bad, no fuel pressure so I'll see if it starts after I swap that out again.
Also make sure the fuel pump relay is good.
06-23-2012, 05:36 PM
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Originally Posted by Johnthepanpire
I just put in a mopar cps from jeep and I'm still only getting .3 volts but I'm using cheap $5 meter, do you think it could be a false reading?
06-23-2012, 06:35 PM
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