1999 Plymouth Breeze compression

The test requires the intake valve to open so air can be drawn into the cylinder. During the compression stroke, the valves have to be closed. Logic dictates the camshaft must be rotating to open and close the valves.

A big word of warning. This is an interference engine. Any attempt to turn the crankshaft without the timing belt installed will bend the open valves. The same thing will happen if the belt breaks while the engine is running. The repair will require removal of the cylinder head to replace the valves.

During normal operation, if the timing belt jumps one tooth, the Engine Computer will turn on the Check Engine light and set a diagnostic fault code in memory. If it jumps two teeth, the computer will shut the engine down to protect it. At three teeth, the pistons will hit the open valves. When replacing the belt, turn the crankshaft at least two revolutions by hand in the normal direction, then double check the timing marks before trying to start the engine.

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