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Shangchai SC27G Series Diesel Engine Troubleshooting Guidelines

Dec. 27, 2017

This is the part six of Shangchai SC27G diesel engine operation and maintenance manual. The main contents of this part is about diesel engine troubleshooting. Shangchai diesel engine is the main part of Shangchai diesel generator, if there is any problem occurs, then it will hurt the machine. Thus, troubleshooting the machine is necessary.


Shangchai SC27G diesel engine operation and maintenance manual

6 Troubleshooting Guidelines

6.1 General

Be calm and careful when the engine has faults, analyze the feature of a fault and judge the cause of a failure according to the following principles.


1) If there is abnormal phenomenon during the operation of the engine, use "see, hear, touch, and smell" to comprehensively judge which part or which system has problems.


"Seen" -to observe the readings of each instrument, and changes of the color of exhaust smoke, coolant temperature and oil pressure.


"Listen" -to listen to the sound of the movements of moving part and its change with a slim metal rod or screw-driver as "stethoscope' on the relevant surfaces of the engine.


"Touch"- to feel for the working condition of the valve train parts and the engine vibration with finger.


"Smell"- to smell abnormal engine odor.


2) The engine should be stopped timely for inspection when the engine suddenly goes wrong or the cause of a failure has been found and the failure will affect the normal engine operation. lf it is difficult to identify the cause of a failure, reduce engine speed and keep the engine running at low-speed without load for observation and inspection in order to avoid a serious failure.


3) When a failure is judged as a serious one or the engine suddenly stops, it should be disassembled for inspection and repair.


4) Failure causes especially big ones as well as solutions to the failures should be recorded in the log of the engine as a reference for next maintenance.


The common faults and correction methods listed in this chapter are only for your reference, In practical work, it should be flexible to find out internal and external causes of malfunctions according to specific engine operation condition and practical experience, provide right remedy to eliminate failures.

6.2 Troubleshooting Guidelines

Some typical and simple diesel engine fault modes, possible causes and troubleshooting steps are listed in the table below. If any one of symptoms occurs in engine operation, it is required to eliminate it by taking appropriate measures. Otherwise, it can lead to severe engine failure. For simple engine faults, you can locate and eliminate them on your own.





Fault Mode





Fault Mode


Engine will not start


Oil temperature and consumption too high



Engine power output low



Coolant in lube oil


Abnormal noise and vibration



Coolant temperature too high


Abnormal smoke



Coolant temperature too low


Abnormal oil pressure



Oil in coolant




Typical system or component fault Mode



Typical system or component fault Mode


Electrical system fault



Fuel feed pump fault


Fuel injection pump fault



Fuel injector fault


Governor fault



Turbocharger fault


Above is the guidelines about Shangchai SC27G series diesel engine troubleshooting. More information about each fault mode details will be provided in the this post and other posts which relates to Shangchai diesel engine. By following the details of each fault mode, users are able to troubleshoot engine faults easier.


Below is the fault mode No.1 information for troubleshooting engine will not start and engine power output low.


(1) Engine will not start



Fault feature



Possible cause




The engine cannot fire after being driven by starter, and fuel in the fuel pump return pipe.



Malfunction of fuel system:

(1) Air in the fuel system


(2) Fuel liquidity affected because of cold weather.


(3) The fuel pipe is blocked.


(4) The fuel filter is blocked


(5) The fuel feed pump cannot supply or continuously supply fuel.


(6) The position of governor control handle is not correct.


(7) Improper fuel injection pump timing.


(8) Very small or no injected fuel flow or no fuel atomization.



Remove air from the fuel system and refer to Section 5.3 for the procedure.


Choose proper fuel specified in this manual based on ambient condition.


Check and clean the pipe.


Clean the strainer and replace the fuel filter.


Check the inlet pipe for leakage and the inlet pipe joint strainer for blockage. If it does not work, check the inlet pipe and feed pump.


The handle should be placed to min. Stable idle speed. Let a professional serviceman inspect the injector, and adjust the injection pressure to the specified value on a test stand. Replace the injector(s) if required.



Engine will not crank when the starting switch gets on.



(1) The wire of circuit connects incorrectly or contact is not good.


(2) (2)Insufficient battery power.


(3) Poor contact between the electric brush and reverser of the starter.


(4) Internal  mechanical  problem hiders the cranking.



Check whether the wire connection is correct or reliable.


Charge battery, or adopt a battery with sufficient output or add some more batteries in parallel.


Repair or replace the carbon bush, clean the reverser surface by wood abrasive paper, and blowing-off, or regulate the spring pressure.


Disconnect the engine with driven equipment and barring the engine to check if the crank train rotate with difficulty due to bearing seizure of crankshaft, connecting rod or piston or wrong camshaft gear timing.



There is no fire while  the fuel injection is right, and there is fuel in exhaust pipe.



Insufficient cylinder compression pressure:


(1) Over wear of piston ring or cylinder liner.


(2) Leakage at valves.



Replace the piton ring and replace the cylinder liner according to the wear condition.


Check the valve clearance, valve spring, valve guide and the sealing condition of the valve seat. Make replacement, repair or grinding if necessary.



Starting time is long and there is no fire.



Too low of ambient temperature.



Use cold starting aid according to ambient temperature.



Above is the troubleshooting details about engine will not start. There are many reasons for engine will not start. User can find corresponding possible cause from the above table and then follow the correction steps one by one to solve the problems.

As it is mentioned above, there are many fault modes in the troubleshooting guidelines, this is the only No. 1 fault mode, more fault mode details will be updated in other posts.



For the information about Shangchai G series diesel engine operation and maintenance, please visit:

Shangchai G Series Diesel Engine Operation And Maintenance Manual

Shangchai G Series Engine Nameplate And Specifications

SC27G Diesel Engine installation and Connection

SC27G Diesel Engine Operation And Engine Start

SC27G Diesel Engine Maintenance Instructions

SC27G Diesel Engine Maintenance

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