1.6L VW Sagitar Engine Cannot Start

Yesterday, I fixed a 2006 VW Sagitar, which has run 80,000 km. The driver said the car engine cannot start suddenly.
I tested the car and found that the starter can work powerfully. But the car cannot start. The start-up system and the power supply were ok. The trouble might be located in ignition system, fuel supply system, mechanical parts, and engine control unit and so on.
Trouble diagnosis:
I connected the VAS5054A, a professional auto diagnostic tool for VAG groups. Read the trouble code of electrical control unit. No trouble codes. Meanwhile, read the static data stream of engine. It was ok. Then, I checked the engine ignition system. The ignition circuits had no problem. I took out the four spark plugs. There were no obvious burns on the electrodes of spark plugs. I cleaned out the carbon deposition and equipped the plugs again. I checked the fuel supply system. I measured the fuel pressure was 3.7bar. It was in the standard valve. It showed that electric fuel pump and its control circuits were ok. I checked the fuel injector circuits. Injector control circuits were ok. I measured the resistance in injector with multimeter. No problem. So I checked the engine mechanical parts. They were ok.

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I tested the systems above, they were ok. I equipped the components again. Tried to start the engine and accelerated it. However the car also failed to start. I took out the spark plugs again. They did not get wet. It meant that the fuel, which entered the cylinder, was too less. When starting the engine, I injected carburetor cleaner into it. The engine can run. The car can start. So I can confirm that the engine cannot run due to thin mixture of fuel and air.
I used oscilloscope to test the Fuel injection pulse width. I found that it was too short. So fuel and air mixture was too thin. And the engine cannot work as usual. I tested the engine speed sensor and the intake air pressure sensor. They were ok.
Trouble shooting:
After changing the engine control unit, the problem was solved.