TROUBLE SHOOTING GUIDE
(CONT)
MECHANICAL KNOCKS
LOOSE, WORN,OR BURNED-OUT MAIN OR CONNECTING ROD BEARINGS.
Slight mechanical knocks which often gave advance warning of bearing troubles in the gasoline engine are not as
easily detected in the diesel. This is mainly due to the higher sound level of the diesel, caused by injection system sounds,
i.e., plunger pumping action, delivery valve action, and injection nozzle opening. For this reason, the operator must pay
;closer attention to the instrument panel gages. Reduced lube oil pressure at normal operating speeds accompanied by
noticeable increase in sound level may indicate bearing failure long before detected by sound only.
VALVES.
BURNED VALVES AND SEATS. Engine misses, especially at low speeds.
WEAK OR BROKEN VALVE SPRINGS. Erratic missing at low or high speeds when under load.
STICKING VALVES. Loss of power or popping sound at air intake or exhaust.
TAPPET NOISE. Excessive clearances cause noise when cold; this decreases at normal operating temperature.
CAMSHAFT.
Noise due to loose bearings or end-play. Generally occurs at about half maximum engine speed.
TIMING GEAR NOISE.
Loose or worn gears rattle or knock; tight gears hum.
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