3-10. TIMING CHAIN COVER, TIMING CHAIN, AND DRIVE SPROCKETS MAINTENANCE
This task covers:
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General mechanic's tool kit:
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Water pump and adapter plate removed
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When measuring timing chain deflection, slack should be
removed from one side before measurement is taken on opposite
In some cases, flanged head fasteners may be present instead
of standard fasteners and washers. In all cases, washers should
be used when replacing a flanged head fastener with a standard
Perform step 1 for M997, M997A1, and M997A2 ambulance
Remove nut (5) and screw (7) from timing chain cover (6).
Remove three capscrews (1) and driven gear (2) from injection pump (9).
Remove two capscrews (18), nut (3), and baffle (4) from timing chain cover (6).
Remove three nuts (11) and washers (10) from injection pump (9) and timing chain cover (6).
Remove four capscrews (13) from timing chain cover (6) and oil pan (14).
Remove five capscrews (16), four washers (15), timing chain cover (6), and gasket (8) from cylinder
block (12). Discard gasket (8).
Using dial indicator, check timing chain (23) deflection midway between camshaft sprocket (22) and
crankshaft sprocket (29). Total deflection must not exceed 0.810 in. (20.6 mm). If deflection exceeds
specification, timing chain (23) must be replaced.
Using dial indicator, check camshaft end play. Camshaft end play must not be more than 0.012 in.
(0.3 mm). If end play exceeds specification, camshaft sprocket (22) and thrust plate (26) must be
inspected for wear after removal.
Remove capscrew (19), washer (20), pump drive gear (21), and camshaft sprocket (22) from
Remove crankshaft sprocket (29), camshaft sprocket (22), and timing chain (23) as an assembly.
Cover oil pan opening to prevent special keys from falling into oil
Remove two special keys (27) from crankshaft (28) and special key (25) from camshaft (24). Discard
special keys (27) and (25).