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One 4.0L Tick

Replacing a ticking camshaft sensor or synchronizer.

Dear Four Wheeler,

I just recently noticed that my Jeep LJ with about 100,000 miles on it has a tick that is distinctly coming from the camshaft sensor, and I guess this part is prone to the shaft wearing out. The tick only starts when the engine warms up, but it's loud. You can put your finger on the top of the sensor and the noise is clearly coming from the unit. My question is if I replace the whole part, do I need to set the engine to top dead center? Or can I just pull the sensor and insert the new one the same way the old one came out? I'm not too savvy on the whole top dead center thing. Am I making it more complicated than it really is? Or will I really mess this thing up if I install the sensor without taking the steps to set the engine at top dead center?

Thanks, Landan Bacon, Peoria, AZ

Hi Landon,
the engine needs to be at top dead center (TDC) for the number one cylinder. That means the timing mark on the harmonic balancer/pulley is lined up with the timing mark on the timing chain cover. The problem is that happens twice during the four-stroke cycle of a 4.0L (and any other gasoline engine in a modern 4x4) so you need to make sure it's at TDC and not 180 degrees out from that. The surefire way to tell if an engine is at TDC for a given cylinder is to pull the corresponding (in this case, number one) spark plug and put your finger over the hole while someone turns the engine over (with a ratchet or breaker bar on the nut on the front of the crankshaft). Just before the TDC marks align, the number one cylinder will push air out the spark plug hole past your finger as it is on the compression stroke.

At that point there should be a small toothpick-sized hole that will align in the cam position sensor. An DC and check to see if the small hole in the cam sensor/synchronizer is lined up or 180 degrees out. If it's 180 degrees out, then you need to turn the crank one more revolution. Once everything lines up as it should you can now pull the cam sensor, but first take a picture of it so you can set the new cam sensor in the exact same position. As you pull up on the cam sensor, the reluctor wheel will turn counterclockwise. You need to have the reluctor on the new part in that same position as it goes into the engine. It will turn clockwise and seat in place the same as the old cam sensor. You will need to make sure the body of the cam sensor is oriented the same as the old cam sensor and then you can tighten the whole shooting match down. You can test this with the toothpick-sized hole or by using the supplied cap (shown in the image) to ensure the new cam sensor is aligned properly. That's it. With any luck the tick (from excess play in the cam sensor shaft) will be gone.

This is the tool included with the new cam sensor/synchronizer. The arrow points toward the rear of the vehicle and engages the reluctor ring in the correct position.