[Rot 911]

Jumped timing means that the camshaft gear driven off the timing chain has jumped a tooth. Usually due to a worn timing chain. The timing will appear correct as to the relationship between the distributor and the pistons, but the valves will be opening at the wrong time. If you pull the timing chain cover you will see a mark on both the cam gear and the crank gear. At TDC they should be facing each other.

The odd thing is that normally when you jump timing you will get low compression readings. I would first try the following: To check the valve/crank timing just pull the valve cover and observe the valves for the #1 cylinder. Pull the spark plugs, hand crank the engine over with a finger covering the spark plug hole for #1, and wait until it starts up on the compression stroke. Make sure you are rotating the engine in the same direction that the starter motor turns it. You will feel the pressure escaping past your finger. That means that the piston is on the way up towards top dead center (TDC). Now, watch the timing mark on the crankshaft damper pulley and continue rotating the engine until the timing mark is at TDC. Both valves must be completely closed at this time. There should be no doubt of it. You can watch the valve action as they close and make certain that they are closed. If either one is even slightly open you have a problem. A compression test will also reveal timing problems. From the above description it should be obvious that the compression on all cylinders will be low if a valve is still open at TDC. So all cylinders will show low compression values.