Efi diesel engine common fault treatment EFI diesel engine maintenance

The electronic fuel injection diesel engine is a diesel engine that uses electronic control of fuel injection and emission. It can freely control the injection amount, pressure value, injection rate, and correct injection time. It is inevitable that the electronic fuel injection diesel engine will have faults during use, so how should it be repaired? The following is a common fault handling of electronic fuel injection diesel engines by Fabaolai Power Generation.

Common Fault Handling of Electronic Fuel Injection Diesel Engines

The typical faults of common electronic fuel injection diesel engines mainly occur in sensors. If the sensor does not work properly, it will have a great impact on the operation of the engine microcomputer control system. The main cause of the fault is that the performance of the components of the electronic control system has changed or is unstable. The work of the electronic control diesel engine mainly relies on the electronic control unit (ECU) to control the fuel supply of the engine under various working conditions, and the amount of fuel supply controlled by the electronic control unit must match the working conditions of the engine. This matching relationship must be a relationship between the condition of the electronic control system and the actual condition of the engine. For example, when the engine throttle is controlled to make the engine run at an economical speed, the engine partial load condition is reflected at this time. The parameters reflecting the partial load state of the engine provided to the electronic control unit by various sensors in the electronic control system should also be data that conforms to the partial load state of the engine. These parameters that mark the engine load state must be consistent with the working state required of the engine. If one parameter cannot reach the actual required value, the engine speed cannot be increased to the corresponding speed. This matching relationship is a basic relationship for whether the engine electronic control system can meet the actual requirements, and it is also the basic guarantee for whether the engine electronic control system can work according to people’s wishes.

In addition, in the process of controlling the engine, the various sensor signals received by the electronic control unit are within the range given by people, and the self-diagnosis system function of the electronic control system is to determine whether the signals of these sensors exceed this range. Only when the signal exceeds the specified range, the self-diagnosis system can know that this signal cannot be used as a control signal. At this time, the self-diagnosis system can determine that there is a fault in the system, have a fault memory, and give a fault code. If the signal does not exceed the given range, but deviates greatly from the actual situation, this inaccurate signal will still cause the electronic control unit to control the engine according to the inaccurate signal provided, causing the engine to malfunction, and the self-diagnosis system cannot give a fault code, which is the root cause of the soft failure of the control system.

Typical fault causes and diagnosis methods of common electronic fuel injection diesel engine electronic control systems are as follows:

Idle switch not closed fault

Idle contact is disconnected, and the pressure sensor ECU determines that the engine is in a partial load state. At this time, the ECU determines the injection amount based on the air flow meter and crankshaft speed signal. However, the engine is working under idle conditions at this time, and the intake volume is small, causing the mixture to be too rich and the speed to rise. When the ECU receives the “mixture is too rich” signal feedback from the oxygen sensor, it reduces the injection amount and increases the opening of the idle control valve, which causes the mixture to be too lean. The speed drops. When the ECU receives the “mixture is too lean” signal feedback from the oxygen sensor, it increases the injection amount and reduces the opening of the idle control valve, which causes the mixture to be too rich and the speed increases.

Diagnostic method: Turn on the air conditioner at idle speed, turn the steering wheel, and the engine speed does not increase, which can prove that this is the fault. Troubleshooting: Adjust, repair or replace the throttle position sensor.

Idle speed control valve (ISC) failure

The correct idle speed of the electronic fuel injection engine is guaranteed by the electronically controlled idle speed control valve. The ECU adjusts the idle speed control valve through calculation according to the engine speed, temperature, throttle switch and air conditioning signals. When the idle speed is lower than the set speed value, the computer instructs the idle speed control valve to open the intake bypass channel or directly increase the throttle opening to increase the intake volume to increase the engine idle speed. When the idle speed is higher than the set speed value, the computer instructs the idle speed control valve to close the intake bypass channel, and the pressure sensor reduces the intake air and reduces the engine speed. Due to oil pollution, carbon deposits on the pressure sensor, the idle speed control valve is sluggish or stuck, and the throttle is not closed in place, the ECU cannot correctly adjust the idle speed of the engine, resulting in unstable idle speed.

Diagnostic method: Check the action sound of the idle speed control valve. If there is no action sound, the idle speed control valve is faulty. Troubleshooting: Clean or replace the idle speed control valve, and use a dedicated decoder to perform basic settings for the idle speed.

Intake pipe leakage fault

Pressure sensor According to the principle of engine speed stability control, under normal circumstances, the opening of the idle control valve and the intake volume strictly follow a certain functional relationship, that is, the idle control valve opening increases, and the intake volume increases accordingly. If the intake pipe leaks, the intake volume and the opening of the idle control valve will not strictly follow the original functional relationship, that is, the intake volume changes suddenly with the change of the idle control valve, and the air flow meter cannot measure the real intake volume, causing the ECU to control the intake volume inaccurately, resulting in unstable engine idle speed.

Diagnostic method: If you hear a “hissing” sound of leakage in the intake pipe, it proves that the intake system is leaking. Troubleshooting: Find the leak, reseal or replace related parts.

Valve timing error fault

The pressure sensor error of the valve timing will cause the valve to open and close at the specified time, resulting in a decrease in the amount of air entering the cylinder. At the same time, the temperature in the intake pipe will increase due to the blowby gas, thereby reducing the degree of cooling of the heating element, and thus output to E. cu voltage signal is low, the injection amount will be reduced, which may cause the engine to run unsteadily and jitter at idle speed. Check the timing mark and readjust the valve timing according to the standard.

Injector dripping or clogging failure

If the injector is dripping or clogged, it will not be able to inject fuel according to the instructions of the ECU, resulting in too rich or too lean mixture, causing individual cylinders to work poorly, resulting in unstable idling of the pressure sensor engine. The lean mixture caused by the blockage of the injector will also cause the oxygen sensor to generate a low potential signal. The computer will issue an instruction to enrich the mixture based on this signal. If the instruction exceeds the control limit, the computer will mistakenly believe that the oxygen sensor is faulty and memorize the fault code. Use a stethoscope to check whether the injector makes a “click” action sound or measure the injection amount of the injector. If the injector has no action sound or the injection amount exceeds the standard, the injector is faulty and needs to be repaired.