FUSO 4M4 – Engine – STRUCTURE AND OPERATION – Timing Chain

• The timing chain is an endless chain with 110 links that connects the exhaust cam sprocket, intake cam sprocket and the idler sprocket.
• The timing chain has mark link plates at three locations that indicate the position at which the crankshaft and the camshaft should take when the chain is installed. There are two plates at the first location and one plate at the second location. The first location (two-mark-link location) must be aligned with the mating mark “ ” on the exhaust cam sprocket and the intake cam sprocket, and the second location (one-mark-link location) must be aligned with the mating mark “ ” on the idler sprocket.
• The chain tensioner gives tension to the timing chain. The chain tensioner has a plunger with a built-in spring.
• When the chain tensioner is installed in position, the plunger directly pushes the tension lever, and the timing chain is tensioned automatically by a force determined by the tension of the plunger spring.
• After the plunger is installed, it is locked in place by a cam provided in the chain tensioner, which prevents accidental deflection of the timing chain while it is driven. Do not crank the engine in the reverse direction after installing the chain tensioner, as this will apply undue forces to the plunger and may cause such undesirable consequences as cam being over ridden by the plunger.


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