MAINTENANCE MANUAL OF GW4D20/GW4D20B TURBOCHARGED DIESEL ENGINES
90
Great Wall Baoding Internal Combustion Engine
Manufacturing Company Limited
Chapter III Malfunction Diagnosis and Troubleshooting
Section I Troubleshooting
When the diesel engine works, due to wearing, distortion, usage and improper maintenance and so on,
the technical condition of each part will worsen gradually; when some technical indicators surpass the
tolerant limits, it indicates that the diesel engine is malfunctioning. When a malfunction appears, the
diesel engine may not work normally if the malfunction is not eliminated in time. In such a case, the
dynamic and economical properties of the diesel engine will degrade and the operation performance will
worsen. Moreover, the parts will be worn too early, and even accidental damage may result.
Some malfunctions such as air presence in the fuel system, air cleaner blockage, and excessive
looseness of the driving belt can be eliminated by necessary technical maintenance and adjustment.
While some malfunctions such as damage of the cylinder head gasket, serious wear of the piston ring,
valve taper face and timing belt, and excessive wear of the bearing shell can not be eliminated by
general maintenance and adjustment due to the defects in relevant mechanisms. In order to eliminate
such malfunctions, it is necessary to remove and repair the diesel engine or replace the parts involved..
Principles for malfunction diagnosis and elimination
(1) Diesel engine malfunctions are usually caused by improper operation or deficient maintenance.
When a malfunction appears, first check if the operation and maintenance regulations are carried out
seriously.
(2) Eliminate the malfunction in time. First check carefully and analyze the cause of the malfunction, do
not remove any part blindly.
(3) The diagnosis and elimination for complex malfunctions should be done by professional persons by
means of appropriate apparatus and specialized equipment. If the user can not judge or cope with the
malfunction, please contact the authorized service station of our company
(4) Only if the diesel engine is in good technical condition can it go on working; working in ―ill‖ technical
condition is not allowed. For in such condition, the parts will wear rapidly and the service life of the whole
vehicle will shorten. Even malignant accidents may be aroused.
Precautions for malfunction diagnosis and elimination.
(1) Do not start the diesel engine when the storage battery is not connected.
(2) Do not disconnect the storage battery from the internal circuits of the vehicle when the diesel engine
is running.
(3) The polarities of the storage battery and the control unit should not be matched reversely.
(4) Always start the diesel engine with the help of storage battery other than the quick start-up device.
(5) Always remove the vehicle storage battery before charging it.
(6) Remove or insert each kind of plug of the electrical control circuit only under the condition that the
storage battery is disconnected (the ignition switch is off).
(7) Diagnose the electronic control diesel engine with suitable equipment as required by the
manufacturer. The diagnostic equipment should be earthed with the cylinder body of diesel engine
during diagnosis.
(8) Do not use traditional methods to diagnose the new type of electronic control diesel engine.
(9) The diagnostic equipment and the control unit of the diesel engine should be connected properly.
(10) Anti-source diagnostics is often applied to the electronic control diesel engine system, and its
process is: first use the diagnostic equipment to find out the possible cause, and then find the exact
position from the peripheral equipment to the control unit gradually and eliminate the malfunction at last.
