How to Check a Timing Chain

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Things You'll Need

  • Breaker bar with appropriate socket

  • Chalk or marker

  • Measuring tape

In some engines the distributor cap and timing chain might be under a filter.

A vehicle's timing chain plays an important role in keeping the engine in good order. It moves the rotor in the distributor and controls the cylinders. A timing chain might become loose if the belt tensioner breaks, the gears get worn, or the chain itself gets stretched. A loose timing chain can throw the engine's timing off, which can lead to poor performance. If you have experience as a home mechanic, you can check the timing chain in a series of steps.

Step 1

Pull the distributor cap off the engine by unbolting it off. Observe the current rotor position.

Step 2

Take a breaker bar with a socket that will fit on the crankshaft pulley. Put it on the crankshaft damper pulley, making sure it fits.

Step 3

Turn the crankshaft pulley clockwise, slowly. Watch the rotor in the distributor. When the rotor starts moving, stop turning.

Step 4

Mark the damper pulley position with chalk or a marker so you can remember the exact position. The mark should be placed on the crankshaft damper.

Step 5

Turn the crankshaft in the opposite direction carefully and slowly. Pay attention to the rotor in the distributor. Once it begins to move, stop turning immediately.

Step 6

Mark the second crankshaft position again.

Step 7

Measure the number of degrees of rotation of the crankshaft. Wrap a measuring tape around the crankshaft damper where the marks are located to measure the circumference of the damper. Then measure the distance between the two marks made.

Step 8

Divide the distance between the two marks by the total circumference of the damper. Multiply the result by 360, which is the total number of degrees in a circle. The result will the give you the amount of degrees between the two marks.

A chain that isn't loose will have about three to five degrees of reverse motion before the distributor begins to turn. A timing chain that is very loose and needs to be replaced will have 10 or more degrees of reverse motion.