I have to guess you have the 2.5L V-6.
If that was a disc, that is to set the critical air gap. It slides off the first time the engine is started. I've never seen a rubber spacer. Chrysler's come with a thick paper spacer stuck to the end. Many aftermarket replacements have a thin plastic rib molded to the end. If you remove those and want to reuse them, you are to cut the remaining part of the rib off and use a new paper spacer from the dealer's parts department.
If you pushed the sensor all the way in when you installed it, most likely it is broken from hitting the flex plate. You can verify that by measuring the voltage on the dark green / orange wire going to the distributor or any injector. You'll find 12 volts there for one second after turning on the ignition switch, then it should come back during cranking. If it doesn't come back, there's no signal being received from the crankshaft position sensor or the camshaft position sensor.
Sunday, February 10th, 2013 AT 3:49 AM