Service manual

4. Troubleshooting
4-1
4.1 Repairing Procedures
When performing failure diagnosis, pay special attention to the followings, observing general cautions.
4.1.1 Safety caution
(1) Removing such cap and/or plug for receiver tank, fuel tanks and pipes where pressure is loaded,
stop the machine and relieve all the interior pressure. Install measuring instruments connected
firmly.
(2) When doing the job with co-worker(s) together, make sure to give signal to the other person(s)
and do not allow other persons to come near to the job site.
(3) Take care not to touch hot portions and not to be involved in turning portions.
4.1.2 Caution during failure diagnosis
(1) Do not make haste to disassemble the unit
If the unit is disassembled urgently.
1. You may disassemble the other portions which are not related with the trouble.
2. The cause of trouble may be missing.
The unnecessary reparations require more spare parts and man-hours, and reparation costs will
increase more. What is worse, you will lose reliance or trust from clients，operators and users.
Therefore, it is absolutely necessary to investigate the trouble more carefully in advance and to
follow the required procedures for failure diagnosis.
(2) Ask the clients about the trouble in details
In order to prevent misunderstanding and incorrect judgment about the trouble, it is necessary
to ask users or operators about the following questions.
1. Is there any other disorder than the trouble he has informed?
2. Anything abnormal occurred before this trouble?
3. Did this trouble happen unexpectedly? Or the unit had been operated in bad conditions before?
4. When and how did this trouble occur?
5. Had he repaired the unit before this trouble occurred?
6. Did he not experience similar trouble before?
(3) Inspection items before starting diagnosis
Sometimes such trouble may be caused owing to routine mishandling of the unit. Before starting
failure diagnosis, check the following items.
1. The engine runs short of engine oil or its oil is not dirty?
2. Check each cable connection for any disconnection.
3. Check the other portions for any damage.
(4) Confirmation of trouble
Discuss with user(s) and/or operator(s) sufficiently about the trouble. As a result, judge whether
their judgment is based on the numerical comparison or sentimental basis. Make him (them)
understand well the reparation or correction you have finished.
Then check and confirm by yourself the cause of the trouble.
Note) Never proceed any investigation or measurement which may cause further greater damage.
(5) Procedures of diagnosis
When you become well experienced, you can find out the cause easily during the process of
confirmation (4). But easy understanding could cause unexpected failure. So check and judge it
according to the following procedures.
1. Check the easiest thing or portion first.
2. Investigate the most possible cause.
3. Check the other things connected to the trouble.
4. Check for the possibility of any other troubles.
5. Start proper and careful investigation on this trouble.
(6) Prevention of repeated occurrence of similar trouble
Even if you have repaired the trouble, unless you get rid of the fundamental cause of the trouble,
it will repeatedly occur. Therefore, perform full investigation of the trouble, and it is absolutely
necessary to remove the basis of the trouble.