Re: The best way to check intermittent spark
It really depends on the timing light. <br /><br />The pickup is inductive, so it detects the magnetic field created when current flowes through a wire. Since if no spark occurs there is no completed circuit, no current flows, no magnetic field is created, and so the pickup detects nothing.<br />Weak sparks will make a weak field, which will set off a timing light depending on it's sensitivity. <br />Although the pickup focuses on feilds within the clamp, sometimes the strong magnetic feild from the ignition coil will set one off too. Test yours to see what kind of proximity you can get to it.<br />Finally, if a plug is fowled, it will still conduct, so it will set off the light too.<br /><br />I hope this answers your questions.<br /><br />EDIT: PS - really cheap timing lights that don't use inductive pickups (clip on ones) light purely from voltage on the spark plug wire. They usually go off at less than 5Kv (which is far too low for an adaquate spark).<br />EDIT 2: PPS - I've seen some poorly designed timing lights fire from (unintentional) capacitive pickup as well. These behave like the above mentioned cheap ones, going off even with no spark at all. Test yours to see.
