Danfoss Motor – Motor : Automatic Flameout, Diagnostic Steps
A, fault phenomenon
There is no difficulty in restarting the engine during the running of the engine or during the running of the car.
B, common causes of failure:
1) Vacuum leak in the intake line.
2) The idle speed is unstable due to improper idle speed adjustment, dirty throttle body, and poor idle control system.
3) Unstable fuel pressure, such as excessive wear or poor contact of the electric fuel pump brush, or blockage of the fuel pump filter.
4) The exhaust gas recirculation valve is blocked or bottom leakage.
5) The fuel pump circuit and the injector drive circuit have faults such as poor contact.
6) Fuel pump relay, EFl relay, ignition relay failure, etc.
7) The ignition system is not working properly. For example, the high voltage is weak, the spark plug is used for too long, the ignition timing is wrong, the ignition coil is in poor contact or the hot state has a turn-to-turn short circuit, so that there is no high-pressure spark or high-pressure spark, the low-voltage line is in poor contact, and the insulating rubber is damaged intermittently.
8) Defective throttle position sensor.
9) The air flow meter or intake pressure sensor is faulty.
10) The coolant temperature sensor and oxygen sensor are faulty.
11) The crankshaft position sensor is faulty, such as no speed signal (plug is not plugged, the crankshaft position sensor signal line is broken, the sensor positioning screw is loose, the gap is out of adjustment, the sensor is damaged, etc.); the crankshaft position sensor signal ring gear is broken, which will cause acceleration. When the flame is turned off; the temperature stability of the electronic components in the crankshaft position sensor is poor, which may cause the signal to be abnormal, which may cause intermittent flameout failure.
12) The ECU is faulty.
C, the general steps of troubleshooting
1) Perform fault self-diagnosis first to check for the presence of a fault code. If yes, find the cause of the fault according to the displayed fault code. Pay special attention to sensors and actuators that affect ignition, fuel injection, idle speed, and gas phase changes (such as engine speed and crankshaft position sensors, camshaft position sensors, coolant temperature sensors, throttle position sensors, idle speed control valves, etc.) There is no fault.
2) If the automatic flameout only occurs in the idle condition, and it can be started after the flameout, it can be checked according to the idle speed and easy to extinguish (see the inspection procedure of idle speed and easy flameout).
3) Use the fault simulation symptom method to vibrate the fuse box and each line connector to see if the fault can occur. Then, further check whether the harness connectors are in poor contact, whether the ground wires are poorly grounded, visually inspect the wiring harness insulation for damage, and intermittent grounding.
4) Using the fault simulation symptom method to change the working environment temperature of the ECU, igniter, etc., reproduce the fault, and then diagnose the cause of the fault.
5) Try to change the ignition coil, spark plug, etc.
6) In the continuous test process, use multi-channel oscilloscope to simultaneously monitor engine speed and crankshaft position sensor, air flow meter, computer 5V output reference power supply voltage and other signals.
7) If there is a phenomenon of surge and acceleration before the flameout, and then slowly turn off the flame, the fault may occur on the oil supply. It can be connected to the fuel pressure gauge. It is best to fix the pressure gauge on the front windshield with transparent glue and test it again. If there is a low oil pressure during the flameout, check the fuel tank, electric fuel pump, fuel filter, oil pressure regulator and fuel pump control circuit.
8) Connect a special diagnostic instrument during the test, read the data before and after the fault occurs, and perform comparative analysis to find the fault.
9) Check and eliminate one by one according to the cause of the failure.
The Danfoss Motor describes the above reasons for the automatic flameout of the engine and the troubleshooting steps, I hope to help everyone.
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