During a no-start diagnosis on an engine equipped with an electronic ignition system, a technician determines that battery voltage is present at the ignition coil positive terminal while cranking. However, when a test light is connected between the coil negative terminal and engine ground, the light glows steadily and fails to pulse as the engine turns over. Which of the following is the most likely cause of this no-spark condition?
- AA malfunctioning alternator that is unable to supply charging voltage to the primary circuit during cranking
- A failed ignition module or switching circuit that is unable to rapidly open and close the primary ground pathCevap
- CA severely rich air-fuel mixture that shorts out the primary winding before electromagnetic induction can take place
- DA misaligned camshaft causing spark generation to trigger during the exhaust stroke rather than the compression stroke
Cevap
A failed ignition module or switching circuit that is unable to rapidly open and close the primary ground path
For an ignition coil to step up low battery voltage to the high voltage required to bridge the spark plug gap, current flowing through the primary winding must be repeatedly interrupted. When the ignition control module or electronic switching transistor opens the ground circuit, the magnetic field built up in the primary winding instantly collapses across the secondary winding, inducing high voltage. A test light that glows constantly without pulsing indicates that the module or switching circuit is not interrupting the ground path.
Adım Adım Çözüm
Anahtar Kavram
Ignition Coil Primary Circuit Switching and Electromagnetic Induction
Alternatif Yöntem
Connecting an automotive digital oscilloscope to the ignition coil negative terminal will display a flat 12-volt baseline rather than the expected switching waveform and 300V to 400V primary flyback spike, confirming the absence of ground switching.
Tahmini Süre:1m 30s