Volkswagen Polo (POLO) can not start

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Mileage of about 92,000 km of Shanghai Volkswagen produced POLO 1. 4 hatchback sedan. BCC type vehicle equipped with EFI engine repair after the accident, the engine will not start.        Troubleshooting:      (1) Failure Cause Analysis      The car was repaired after an accident occurs can not start, the main possible causes ignition system, fuel supply system and electronic engine control systems.      (2) the troubleshooting process        First, read with the VA G1552 fault diagnostic fault information, the results did not find fault code. Then start the engine, no signs of fire. Remove the pen ignition coil, spark plug and make grounding, check flash, and found the spark is weak; pull injector check injector case, there are oil spray. After measuring cylinder pressure, only 750kPa, from each lexia 3 spark plug hole, add a little oil, cylinder pressure up to 1050kPa. When re-starting the engine, I heard the sound of the trachea into the temper, and there put guns into the exhaust pipe, ignition disorder symptoms.        Disconnect the crankshaft position sensor and then start the engine can smoothly start. Remove the transmission found that the sensor triggers the vertical position of the reference mark and the sensor on the wheel actually have 28 teeth (normal should be 14 teeth), trigger wheel mounted on the positioning hole is just aligned with the sensor. To conclude, before the repairman when installing the sensor trigger wheel, mistakenly install the locating holes as marked. Led to the crankshaft position sensor sends the wrong crankshaft position signal, causing the engine ignition confusion, unable to start.      (3) failure treatment measures        Replacement of the crankshaft sealing flange and crankshaft position sensor, the arrow (mark lower right corner) to install the positioning hole and sealing flange sensor trigger wheel is aligned with the tool slowly into, installed sealing flange positioned bolts, then other accessories and gearbox refitted. Then start the engine, a smooth start troubleshooting.        Failure Analysis: crankshaft position sensor trigger wheel car with a (60-2) teeth, teeth that is triggered by 60 teeth uniform, a location removed two teeth, used to determine the crankshaft position marker. When the engine crankshaft, for rotation therewith trigger wheel per revolution of the sensor 58 generates a pulse Tuirel S777 signal for calculating a speed of the engine, and the larger interval of the pulse signal, for determining the position of the crankshaft. Trigger wheel installed in the wrong place, the engine ECU can not accurately determine the position of the crankshaft in accordance with the signal of the crankshaft position sensor, and therefore generate an error caused by the ignition of the ignition signal confusion.        ECU self-diagnostic program can only be based on whether the sensor signal is missing, super-sector to determine whether the fault for the crankshaft position sensor signal is only relative to the crankshaft position misalignment can not diagnose it is a failure, it will not record fault information.        Unplug the crankshaft position sensor engine can be started, this is because the engine ECU to run self-diagnostic system with fault function, when there is no crankshaft position sensor signal, the self-diagnostic program will determine the crankshaft position sensor and circuit failure, and failure to start running the program with camshaft position sensor signal to calculate engine speed and crankshaft position to judge and control the ignition and fuel injection, the engine can run. Of course, in this case the engine is "sick to keep working."