Troubleshooting of Yuchai 4D24/4D24T Diesel Engine

Insufficient preheat:

1. Under cold conditions, starting before the cold start indicator light flashes off;

2. The battery voltage fluctuation is not normal in the pre heating process showed on the multimeter or the diagnostic instrument.

1. Check whether the preheat circuit wiring is good,

2. Check whether the battery capacity is sufficient.

Fuel quality does not meet the requirements:

1. Use incorrect grade of fuel;

2. Excessive fuel impurities;

3. Excessive water in fuel;

Replace by qualified fuel, and clean fuel circuit.

Fault code in ECU memory:

1. Fault codes can be read through the diagnostic instrument;

2. Fault flash codes can be read through diagnostic request button;

3. Electronic control system fault information can be read through CAN meter.

1. If the fault code or fault flash code information clearly points to a specific electronic control components, inspect and repair the corresponding faults of sensors, actuators and its line;

2. After repairs, use the diagnostic instrument or diagnostic request button to delete the fault historical information, and fully running engine to confirm ECU memory without fault code information.

Water temperature sensor

1. Check the temperature sensor connector and circuit;

2. Check if the temperature sensor dirty or damaged.

Low pressure fuel circuit failure

1. Make sure there is enough diesel in the tank;

2. Discharge of air in low pressure fuel circuit;

3. Check the pipes, the joint tightening

condition, and, whether the hose and

the joint are affected by extrusion, damage, or the diameter is not correct;

4. Check whether the fuel filter,

pre-filter are blocked or damaged;

5. Check whether  the  fuel  tank ventilation device is blocked or contaminated (open tank cover and check pumping sound);

6. Check whether the fuel pump and

the inlet & outlet of filter are connected incorrectly.

7. Check whether transfer pump is failure.

Intake system block or leakage

Check air filter, air inlet pipe, clean or replace air filter element.

Exhaust back pressure is too high

Check valve timing and adjust if necessary,

Turbo system failure

1. Check and eliminate the leakage from the pipe and connection;

2. Turn the turbocharger shaft to confirm whether turbocharger shaft block or loosen;

3. Check if turbocharger compressor impeller and turbine damaged.

Fuel pipeline leakage or block

Check the sealing condition of the fuel pipe and the joint, the blockage of the fuel filter, replace the pre-filter element or fuel filter element when necessary.

Diesel engine coolant temperature is too high

Check and repair radiator, thermostat, fan belt tension adjustment.

Injector fault

1. Check injector atomizing;

2. Check injector shim thickness correct or not;

3. Check injector protrusion height correct or not.

High-pressure fuel pump failure:

1. Fuel channel blocked in high-pressure fuel pump;

2. High-pressure fuel pump plunger wear;

3. Relief valve of high-pressure pump blocked, contaminated or stuck.

Clean or replace the high-pressure pump, replacement of clean fuel, full road test.

Cylinder air tightness and compression performance failure:

1. Insufficient compression pressure;

2. Excessive wear of piston ring;

3. Valve leakage.

1. Replace the piston ring, or machining the cylinder hole if necessary;

2. Check sealing of valve clearance, valve spring, valve guide and valve seat, grinding valve seat if sealing is not good;

3. Screw down, clean or replace;

4. Removal of combustion chamber carbon deposition;

5. Check if the crankshaft, connecting rod bending etc.

The control function of the other control module on CAN network and the control function of the diesel engine ECU are interfered

Alternately disconnect other control modules on the CAN network until the communication of function is restored.

Additional power consumption is too large

Check whether the working cycle time of the cooling fan and the driving device of the diesel engine are working normally.

Internal damage of diesel engine

Check and replace damaged parts at the service station.

Fault code in ECU memory:

1. Fault codes can be read through the  diagnostic instrument;

2. Fault flash codes can be read

through diagnostic request button;

3. Electronic control system fault information can be read through CAN meter.

1. If the fault code or fault flash code information clearly points to a specific electronic control components, inspect and repair the corresponding faults of sensors actuators and its line;

2. After repairs, use the diagnostic instrument or diagnostic request button to   delete the fault history information, and fully running engine to confirm ECU memory without fault code information.

Crankshaft sensor and its circuit fault

1. Check crankshaft sensor connector and circuit;

2. Check whether installation clearance between crankshaft sensor and the signal panel is installed correctly;

3. Check whether the crankshaft sensor is dirt or damage.

Idle speed abnormal sound

1. Check if there is air in fuel pipes;

2. Check whether injector is normal or not;

3. Fuel filter has a stagnant water cause insufficient fuel supply.

Abnormal sound during acceleration

1. Check whether air filter is clean, or blocked. Replace the air filter if necessary.

2. Check whether intake and exhaust pipes connected well or leak, air leakage need to be solved.

3. Check whether turbocharger connection pipes are fastened, cleaned, sealed well, or cracked, clean or replace if necessary.

4. Turbocharger bearing broken, rotating parts and housing collide with each other. Turbocharger surge due to too high altitude.

Mechanical noise / Abnormal sound during acceleration

1. Check timing mark.

2. Check whether the valve timing and valve clearance is correct, adjust if necessary.

3. Check whether the valve spring is abnormal, replace if necessary.

4. Serious wear of camshaft or rocker shaft .

5. Confirm the sealing of cylinder gasket, replace if necessary.

6. Confirm whether the breather and

piston ring are working properly, replace if necessary.

7. Piston clearance is too large;

8. Timing mechanism worn.