When you press the start pushbutton the ECU is alerted assuming that the starting requirements are satisfied -- transmission in neutral, clutch disengaged, side stand raised.
The ECU expects feedback from the crankshaft position sensor, the cylinder identification sensor, and the intake air pressure sensor when the engine is cranking and running. The ECU gets no direct feedback from the starter relay or starter motor.
So if you press the start pushbutton and no crankshaft position sensor input, etc. is received what might be the problem? The ECU assumes that the starter relay energized the starter motor and the crankshaft should have rotated. So investigate the crankshaft position sensor.
The starter relay contacts are eroded every time you release the start pushbutton and the relay contacts are opened. Closing the contacts doesn't damage them much, only when they are opening.
The contacts suffer the most damage when the engine doesn't start. The starter motor is delivering full output and the relay contacts must interrupt that full load current. If the engine starts, the starter motor load drops off with a corresponding reduction in current. It's easier and less damaging to interrupt a smaller current.
The ECU expects feedback from the crankshaft position sensor, the cylinder identification sensor, and the intake air pressure sensor when the engine is cranking and running. The ECU gets no direct feedback from the starter relay or starter motor.
So if you press the start pushbutton and no crankshaft position sensor input, etc. is received what might be the problem? The ECU assumes that the starter relay energized the starter motor and the crankshaft should have rotated. So investigate the crankshaft position sensor.
The starter relay contacts are eroded every time you release the start pushbutton and the relay contacts are opened. Closing the contacts doesn't damage them much, only when they are opening.
The contacts suffer the most damage when the engine doesn't start. The starter motor is delivering full output and the relay contacts must interrupt that full load current. If the engine starts, the starter motor load drops off with a corresponding reduction in current. It's easier and less damaging to interrupt a smaller current.