How to Check a Timing Chain

by Vanessa Lascano
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New car petrol engines image by Christopher Dodge from

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.

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.

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