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Common Trouble of Yuchai 4D24/4D24T Engine and Removal Methods

Jan. 07, 2020

6. Common trouble of Yuchai 4D24/4D24T diesel engine and removal methods

Note: This manual describes some typical engine operation problems, the reasons and the solutions.

Warning: Implementation of this chapter of the fault diagnosis and elimination steps may result in machinery damage or personal injury or even death. It must be by trained technicians implement fault diagnosis and troubleshooting work. For not listed in this chapter the diagnosis and exclude steps and symptoms, please contact Raywin.

To make a fault diagnosis, please follow the following recommendations:

1) Careful analysis of the problem before action;

2) Start with the most easy and obvious place;

3) Find the root causes and eliminate the problem.

In order to find fault in time, protect the diesel engine, greatly shorten the maintenance time, improve the utilization efficiency of the diesel engine, RAYWIN 4D24, 4D24T engine's ECU is with fault diagnosis function. ECU can make diagnose judgement by analyzing electric signals, to diagnose the most electronic components and a few mechanical component failures. Once the fault of electronic control system is detected by ECU, it will produce a corresponding fault code and save the information into ECU memory.

I. Fault indicator

1) These fault indicator is located on the dashboard:

2) These are generally red color (for more details please refer to machinery manual);

3) These are self-checking after electricity, fault indicator light turns off after 2 seconds;

4) Light turns on once the failure of electrical failure system appears;

5) General fault, fault indicator lighting;

6) Serious faults, fault indicator flashing;

7) Fault disappears, the malfunction indicator light off automatically.

II. fault flash code reading method

Read fault flash code method through fa ult indicator lamp:

1) These are the ignition switch in the ON place;

2) with or without load;

3) Press diagnose button to activate the fault diagnosis flash code;

4) Each operation gets one fault flash code, all fault flash codes can be got one by one;

5) Fault flash codes include current and historical code;

6) Reading the code after cleaning, which is the current fault code.

For example, using the above method to read ECU memory warning lamp line fault, fault flash code 553, the flashing way of the fault indicator light is as follows:

Yuchai engine fault code

III.  the method of cleaning the historical fault code

In practical application, it can remove the historical fault code in ECU memory conveniently and quickly by using diagnose button, the detail is as follows:

Press diagnosis request button;

Put the ignition button to the OFF place for more than 18 seconds, until ECU power off;

Put the ignition button to the ON place, ECU power on;

ECU power on for 6 seconds (4~8 seconds), then release of the diagnosis request button.

6.1 Diesel engine cannot start

Failure cause


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.

Electronic control system cannot power on

Check wiring harness and fuse, main power switch, especially ignition switch.

Method for quickly judging fault:

1. Fault indicator light does not light when the power on self-test;

2. The diagnostic instrument cannot be connected;

3. The power line in the throttle;

connector cannot be 5V voltage;

Battery voltage deficiency

Replace battery or charge

The starter does not work

1. Check the switches and wiring is intact, try to use emergency start (continued to press  the switch-on request button for more than 5 seconds) to observe starter action;

2. Check the start request button, start control relay and its circuit;

3. Check whether the shutdown button is in the off status;

4. Check the starter.

ECU memory has the fault code:

1. The fault code can be read through the diagnostic instrument;

2. The fault flash code can be read by   the diagnosis request button;

The fault information of the electric control system can be read through the CAN meter.

1. Check and repair the relevant parts or system according to the fault code or the fault code information, if the fault information from crankshaft/camshaft, then jump to step four;

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

Unable to set up work schedule:

1. During the starting, the diagnostic instrument cannot monitor the speed changing;

2. All crankshaft signals are lost;

3. Oscilloscope displays timing installation phase error;

1. Check if the crankshaft signal sensor is in good condition;

2. Check if crankshaft connector and the conducting wire is intact;

3. Check whether the crankshaft signal disc is damaged or nor / dirty attachment (through the sensor signal hole);

4. Check the gap between crankshaft signal sensor and signal disk installation (generally 1+0.5mm);

5. If disassemble the signal plate and other components during maintenance, check if the timing phase assembly is correct.

Low pressure fuel circuit failure

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

2. Elimination 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.

Injector fault

1. Check injector atomizing;

2. Check whether 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 matching the cylinder hole of 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.

Other mechanical components failure

1. Inspect fuel system/oil system;

2. Inspect intake/exhaust system;

3. Check if the filter is blocked, etc.


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