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Service Manual Mitsubishi SL-Series diesel engines
Version 08/2004
ENGLISH
DETERMINING WHEN TO
OVERHAUL THE ENGINE
OVERHAUL INSTRUCTIONS
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OVERHAUL INSTRUCTIONS
4 DETERMINING WHEN
TO OVERHAUL THE
ENGINE
Generally, when to overhaul the engine is to be
determined by taking into account a drop in
compression pressure as well as an increase in lube oil
consumption and excessive blowby gases.
Lower power or loss of power, an increase in fuel
consumption, a drop in lube oil pressure, hard starting
and excessive abnormal noise are also troubles.
These troubles, however, are not always the result of
low compression pressure and give no valid reason for
overhauling the engine.
The engine develops troubles of widely different
varieties when the compression pressure drops in it.
Following are the typical troubles caused by the
compression pressure failure:
1. Low power or loss of power
2. Increase in fuel consumption
3. Increase in lube oil consumption
4. Excessive blowby through breather due to worn
cylinders, pistons, etc.
5. Excessive blowby due to poor seating of worn inlet
and exhaust valves
6. Hard starting or failure to start
7. Excessive engine noise
In most cases, these troubles occur concurrently.
Some of them are directly caused by low compression
pressure, but others are not. Among the troubles listed
above, (2) and (6) are caused by a fuel injection pump
improperly adjusted with respect to injection quantity or
injection timing, worn injection pump plungers, faulty
injection nozzles, or poor care of the battery, starter
and alternator.
The trouble to be taken into account as the most valid
reason for overhauling the engine is (4): in actually
determining when to overhaul the engine, it is
reasonable to take this trouble into account in
conjunction with the other ones.
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