Positioning Crankshaft to Number 1 TDC

POSITIONING CRANKSHAFT TO #1 TDC, Compression

NOTE: If the timing belt is broken, pre-position only the crankshaft and ignore references in this article to compression stroke, and camshaft. Rotating the camshaft with a broken timing belt may damage the valves.

WHY
Timing belt installation alignment marks correspond to the crankshaft positioned at number 1 Top Dead Center (TDC), during the compression stroke. Moving the crankshaft to this point prior to removing the belt allows you to verify the original alignment of the crankshaft and camshaft. This also reduces crank/cam pulley movement once the belt is removed which helps to minimize any possible confusion.

The alignment marks may be dirty and difficult to locate. Pre-positioning the crankshaft will make it easier to locate the marks.

HOW
- Verify the ignition key is in the "OFF" position or is removed from the vehicle.
- Connect a compression gauge to number 1 cylinder. Using a remote starter switch, slowly bump (tap the switch lightly) the engine until compression just begins to register on the gauge.

NOTE: The crankshaft is now approaching TDC on number 1 cylinder, during the compression stroke.

- Remove the remote starter switch and disconnect the negative terminal of the battery.
- Using the crankshaft bolt, rotate the crankshaft till the timing indicator is at TDC.