Top Dead Center (TDC) for number one piston — locating
1. Top Dead Center (TDC) is the highest point in the cylinder that each piston reaches as it travels up the cylinder bore. Each piston reaches TDC on the compression stroke and again on the exhaust stroke, but TDC generally refers to piston position on the compression stroke.
2. Positioning the piston(s) at TDC is an essential part of certain procedures such as camshaft and sprocket removal.
3. Before beginning this procedure, make sure the transmission is in Park and apply the parking brake or block the rear wheels. Disconnect the cable from the negative terminal of the battery (see Engine electrical systems).
4. In order to bring any piston to TDC, the crankshaft must be turned using a socket, extension and ratchet or breaker bar. When looking at the front of the engine, normal crankshaft rotation is clockwise.
5. Remove the spark plugs (see Tune-up and routine maintenance) and install a compression gauge in the number one spark plug hole (see illustration). It should be a gauge with a screw-in fitting and a hose at least six inches long.
i. 5 A compression gauge can be used in the number one plug hole to assist in finding TDC
6. Loosen the right front wheel lug nuts, then raise the front of the vehicle and support it securely on jack stands. Remove the wheel and, if necessary, the inner fender splash shield.
7. Rotate the crankshaft using a socket and breaker bar or ratchet while observing for pressure on the compression gauge. The moment the gauge shows pressure indicates that the number one cylinder has begun the compression stroke.
8. Once the compression stroke has begun, TDC for the compression stroke is reached by bringing the piston to the top of the cylinder.
9. Continue turning the crankshaft until the notch in the crankshaft damper is aligned with the «TDC» or the «0» mark on the timing chain cover (see illustration). At this point, the number one cylinder is at TDC on the compression stroke. If the marks are aligned but there was no compression, the piston was on the exhaust stroke; continue rotating the crankshaft 360-degrees (one turn).
i. 9 Align the groove in the damper (A) with the «0» mark on the timing chain cover (B)
10. After the number one piston has been positioned at TDC on the compression stroke, TDC for any of the remaining cylinders can be located by turning the crankshaft 180 degrees and following the firing order (refer to this Chapter’s Specifications). Rotating the engine 180 degrees past TDC #1 will put the engine at TDC compression for cylinder #3.