I came up with an alternative method to check the slack in the timing chain for the Jeep/Chrysler 3.8L that only requires removing the cam sensor. Below is a pic of the empty hole with the cam sensor removed.


The factory service manual does have a test for measuring slack in the timing chain, but it can only be done with the timing cover and oil pan removed -- Which is 95% of the job to replace the chain.

Here's the alternative method:

1. Clean around the cam sensor so that dirt isn't going to fall into the engine when it is removed.
2. Mark an indicator line, or note some other reference for how deep the sensor is in the hole. If this step is missed or the line disappears, no worries. The gap between the sensor nose and cam sprocket will get set later regardless.
3. Remove the connector, loosen the bolt, and remove the cam sensor. If it hasn't been out in a while it will take some wiggling.
4. Paint a 1/4 inch wide mark on the crank pulley. That's worth about 5 degrees of crank movement. Set up a suitable pointer so that the crank can be rotated and the pointer will show how far the crank rotates from the edge of the 1/4 inch white mark.
5. With a breaker bar and socked on the bolt for the crank pulley, rotate the crank until it just passes the mark, and the pointer is at the edge of the mark.
6. While looking down the hole for the cam sensor at the timing chain, slowly rotate the crank in the opposite direction until the timing chain just starts to move.
7. Note how far the crank moved to take up the slack in the timing chain. If it exceeded 1/4 inch (5 degrees), it's very close to, or exceeds, the wear limit. I'd prefer less than 3 degrees, a bit over 1/8".

Cam sensor installation
The factory method is to use a sacrificial spacer that's glued on the nose of a new sensor, and replacement spacers can be purchased. The sensor is pushed in against the cam sprocket, the bolt is tightened, and the gap is set by the thickness of the spacer (about 0.03"). The paper spacer probably dissolves in hot oil after being torn off by the edges on the cam sprocket that the sensor is sensing.

Here's an alternate method to set the gap and install the cam sensor:

1. With a clean sensor and some grease on the o-ring, push it in until it touches the cam sprocket. Optionally make a pencil mark in the bore of the hole above the edge of the sensor.
2. Retract the sensor about 0.03" (approx 1/32 inch). For reference, use the edges of the hole, pencil mark, etc.
3. Repeat steps 1 and 2 above to verify the gap appears correct, then tighten the bolt that holds the sensor to the timing cover. As long as there is some clearance between the sensor and sprocket, the worst that will happen is a DTC for the cam sensor if the gap is outside the tolerance of the sensor. I simply eye-balled 1/32" and it worked every time. Guessing that a decent tolerance for the gap to shoot for is 0.02 to 0.04 inch.
4. Install the connector.

The timing chain replacement thread is at this link...