Case 980 Excavator Service Manual

Table of Contents

1. General
2. Engines
3. Fuel System
4. Hydraulics
5. Track and Suspension
6. Power Train
7. Brakes
8. Mounted Equipment

Manual Extract Engine Preignition

Preignition is the igniting of the fuel before the normal ignition occurs. This causes wild pinging, severe knock, and power loss. High temperature and pressure from preignition usually burns a hole through the center of the piston. The following are causes of preignition:

A. Carbon deposits that remain incandescent.
B. Valves operating at higher than normal temperature because of excessive guide clearance or improper seal with valve seats.
C. Hot spots caused by an inefficient or damaged cooling system.
D. Nozzles set at wrong cracking pressure.
E. Detonation or conditions leading to it.
F. Sharp edges in combustion chamber.
G. Wrong or contaminated fuel.