Valve Timing: Description

Fig 1: Timing Drive System Diagram

Courtesy of DAIMLERCHRYSLER CORP.

1 - CAMSHAFT TIMING MARK ALIGNS WITH SINGLE PLATED/DIMPLED LINK

2 - CAMSHAFT SPROCKET

3 - RIGHT TIMING CHAIN GUIDE (MOVABLE)

4 - LEFT TIMING CHAIN GUIDE (FIXED)

5 - PLUG WITH SEAL RING

6 - OIL RESERVOIR CAP

7 - TIMING CHAIN TENSIONER

8 - CRANKSHAFT SPROCKET

9 - TIMING CHAIN

10 - CRANKSHAFT TIMING MARKS ALIGN WITH DOUBLE PLATED/DIMPLED LINKS

The timing drive system consists of the following. See Fig 1:

Timing Chain (9)
Camshaft Sprocket (2)
Crankshaft Sprocket (8)
Right Timing Chain Guide (Movable) (3)
Left Timing Chain Guide (Fixed) (4)
Timing Chain Tensioner (7)/Oil Reservoir Cap (6)/Plug with Seal Ring (5)

The camshaft sprocket (2) is attached to the front of the camshaft and is used with the timing chain (9) and crankshaft sprocket (8) to turn the camshaft. The camshaft position sensor target is part of the sprocket and is used with the camshaft position sensor to provide the PCM with valvetrain position information.

The timing chain tensioner (7) is installed in the right side of the engine block. Using engine oil pressure, the tensioner applies constant pressure to the right side (movable) timing chain guide (3) , which in turn applies pressure to the timing chain (9). Also as the tensioner extends, it rachet locks in position to provide constant timing chain tension. An oil reservoir cap (6) attaches to the timing chain tensioner (7) to provide an available "pocket" of oil to the tensioner during initial start up.