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The Chevrolet sports car engine flameout after a few seconds
  • Automotive

A Chevrolet sports car with a mileage of about 150 thousand km, equipped with V8 electronic fuel injection engine and automatic transmission. User response: when the vehicle starts the vehicle, the engine will turn off after running for a few seconds. The engine uses the HEI-EST ignition system (high energy electronic ignition system). Check high pressure fire, normal. The carburetor cleaning agent is injected into the intake manifold and the engine runs barely. The use of external pump instead of the original vehicle fuel pump, the fuel pressure built up, still no vehicle. The test lamp is straddled between the two terminals of the fuel injector plug. When the vehicle starts, the test lamp flickers, but after 2S, the fire is turned off. Since the grounding circuit of the injector is directly controlled by the power system control module (PCM), the power system is self diagnosed without any fault code. PCM is found on the inside of the front passenger's foot pit guard board to measure the line connection between the wire harness terminals and the injector. It is confirmed that 4 injectors in the left column cylinder share one ground control line and the 4 injectors in the right cylinder share another ground control line, which are well connected. The HEI-EST ignition system is equipped with a distributor, and the ignition control module and the crankshaft position sensor are arranged inside the distributor. The ignition control module has 4 wires connected to PCM: EST output, reference input, bypass control and reference signal (low). When the engine speed is lower than 400r/min, the ignition timing is controlled by the ignition control module. If the engine is higher than 400r/min, the ignition timing is controlled by PCM. The sign of the ignition timing conversion is that the 0V voltage of the bypass control wire is changed to 5V, and the voltage of the EST output conductor is present. Combined with the above working principle, the voltage of the bypass control wire is measured, and the result is switched from 0V to 5V, which indicates that PCM receives the engine speed signal. Because the signal is used to control the fuel injector and fuel pump relay, and the fuel pump has been operated, there are two reasons to determine the cause of the failure. One is the damage of the PCM's injector drive circuit, the two is the engine anti-theft function, and the fuel injection function is interrupted. Check PCM, no signs of damage were found. The car is equipped with Passkey II anti-theft system, mainly composed of the ignition key and the Passkey control module (anti-theft control module). Its principle is that a black resistance block in the ignition key uses an anti-theft identification element, inserts the ignition key into the ignition switch, and the Passkey control module uses two guides on the neck of the ignition switch. The line reads the resistance value of the resistance block and compares the resistance with the resistance value of the internal memory. If the value is consistent, the fuel injection locking function is relieved and the starting is allowed. If the value is not consistent, the fuel injection function is relieved. Check the ignition switch and find that the line is changed. Two signal lines used to detect resistance blocks were found, and an ignition key was also placed in the middle. Remove the ignition key of the original vehicle and debug it repeatedly with a slide rheostat. The Passkey control module is found inside the instrument room, and the result is not abnormal. Referring to the relevant circuit diagrams, it is known that a dark blue conductor is connected between the Passkey control module and the PCM, and the wire is the anti-theft data line. Is it possible to use the anti-theft data line to start the engine? I have come up with a simple method, to find a bolt, thread one end to ground, in the process of starting the anti-theft data line across the thread area, it can simulate a group of 5V pulse signals. After several tests, the engine finally worked, indicating that the PCM and Passkey control modules are all good, and the problem is that the wiring is bad. Repair the line, test the car, the fault is completely eliminated. Judging whether PCM and Passkey control module is normal is the key to maintenance work. It is necessary to explain that, through a simple method to simulate the anti-theft pulse signal, it can make the engine run up, the Passkey 11 anti-theft system does not have variable code function, it is easy to be cracked.

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