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Komatsu 3D82AE,3D84E,3D88E,4D88E,4D98E,4D106,S4D84E,S4D98E,S4D106 TROUBLESHOOTING

Preparation before troubleshooting

If the signs of a trouble appear, it is important to lecture on the countermeasure and treatment before
becoming a big accident not to shorten the engine life.
When the signs of a trouble appear in the engine or a trouble occurs, grasp the trouble conditions fully
by the next point and find out the cause of sincerity according to the troubleshooting. Then repair the
trouble, and prevent the recurrence of the trouble.
1) What’s the occurrence phenomenon or the trouble situation? (e.g. Poor exhaust color )
2) Investigation of the past records of the engine
Check a client control ledger, and examine the history of the engine.
*Investigate the engine model name and the engine number. (Mentioned in the engine label.)
Examine the machine unit name and its number in the same way.
* When was the engine maintained last time?
* How much period and/or time has it been used after it was maintained last time?
*What kind of problem was there on the engine last time, and what kind of maintenance was dane?
3) Hear the occurrence phenomenon from the operator of the engine in detail.
5W1H of the occurrence phenomenon : the investigation of when (when), where (where), who
(who), what (what), why (why) and how (how)
* When did the trouble happen at what kind of time?
* Was there anything changed before the trouble?
* Did the trouble occur suddenly, or was there what or a sign?
* Was there any related phenomenon.
.(e.g. Poor exhaust color and starting failure at the same time)

4) After presuming a probable cause based on the above investigation, investigate a cause
systematically by the next troubleshooting guide, and find out the cause of sincerity.

Quick Reference Table for Troubleshooting

The following table summarizes the general trouble symptoms and their causes. If any trouble symptom occurs, take corrective action before it becomes a serious problem so as not to shorten the engine service life.

Quick Reference Table for Troubleshooting


Quick Reference Table for Troubleshooting

Quick Reference Table for Troubleshooting -2

Troubleshooting by measuring Compression Pressure

Compression pressure drop is one of major causes of increasing blowby gas (lubricating oil
contamination or increased lubricating oil consumption as a resultant phenomenon) or starting failure.
The compression pressure is affected by the following factors:
1) Degree of clearance between piston and cylinder
2) Degree of clearance at intake/exhaust valve seat
3) Gas leak from nozzle gasket or cylinder head gasket
In other words, the pressure drops due to increased parts wear and reduced durability resulting fromlong use of the engine.
A pressure drop may also be caused by scratched cylinder or piston by dust entrance from the dirty air cleaner element or worn or broken piston ring. Measure the compression pressure to diagnose presence of any abnormality in the engine.

(1) Compression pressure measurement method
1) After warming up the engine, remove the fuel
injection pipe and valves from the cylinder to be measured.
2) Crank the engine before installing the compression gage adapter.
*1) Perform cranking with the stop handle at the stop position (no injection state).
*2) See 12.2-18 in Chapter 12 for the compression gage and compression gage adapter.
3) Install the compression gage and compression gage adapter at the cylinder to be measured.
*1)Never forget to install a gasket at the tip end of the adapter.
4) With the engine set to the same state as in 2)*1),crank the engine by the starter motor until the compression gage reading is stabilized.

Troubleshooting by measuring Compression Pressure

(2) Standard compression pressure Engine compression pressure list (reference value)

Standard compression pressure

(3) Engine speed and compression pressure (for reference)

Engine speed and compression pressure (for reference)



(4) Measured value and troubleshooting When the measured compression pressure is below the limit value, inspect each part by referring to the table below.

Measured value and troubleshooting


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