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01 Jeep only Starts After Sitting

Forestgreenxj

NAXJA Forum User
Location
Wisconsin
So I just bought my first xj its an 01 and it only started after sitting for about 8 hours and I replace the CPS and now it wont start at all, butt will crank and crank and crank, any help would be appreciated
 
Test the fuel pressure. Test the check valve leak down. If the fuel pressure is correct, suspect the Crankshaft Position Sensor (CPS) or its wire plug and wiring. Wiggle and inspect all the wire harnesses and wire plugs. Look melted/chafed insulation and corrosion.

Cheap Chinese CPS, often sold with a "lifetime Warranty", are well known to be out of specification or even failed right out of the box. Only buy genuine Jeep engine sensors.
 
there has been people that have gotten bad parts out of the box. i would try a better quality one.

once it gets running does it stay running and run smooth?
 
I have fuel at the rail I pressed the valve and fuel sprayed out, and when she starts up she runs like a dream. And the replacement CPS was from autozone.
 
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Do CPS's fail when the motor is hot? I didn't think so. That's why I suggested the search I did. Everything suggested so far seems like the opposite of his issue. Unless I read it wrong, it starts fine the first time but has to sit for eight hours to start again. I bet it just needs to cool sufficiently to make one of the sensors on the intake start working again. Or maybe the wiring to the CPS has sat on the exhaust header and now is toast.
 
Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again when it cools back down.

The root cause may in fact be something else, but so many "Lifetime Warranty" CPS have been total crap that the CPS cannot be ruled out as the primary cause until it is genuine Jeep part.
 
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With the CPS ruled out as the primary cause, a faulty Cam Sensor would make a likely suspect, especially if you have a related trouble code.
 
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