In the old Forum I posted a thread on using a mobile phone app to detect the magnetic field from coils, relays even fuel injectors. This tool will also do the job Voltcraft MS-410 Magnetic field detector pen, it glows violet when near a magnetic field. For Fuel Injectors it needs to be used in dim lighting to show up. Prices varies a lot so if buying it pays to shop around mine cost me about £12/15euro/18$US.
Nice! I've been playing with that app since you posted about it, came up with some more questions. Wondering if a dead secondary winding in a coil would result in no reading, or just a dead primary? There are limitations, of course, just playing with how far you can take it.
It will only show up primary or control problems which is the first stop in a cranking no start, but I have actually found it most useful for locating the fuel pump relay.
The cars I work on aren't prone to coil primary ignition faults but I see a lot scondary high tension faults. About 16 years back MG-Rover changed over from a distributor system to a wasted spark sharing a plug top coil, initially we were seeing a lot of coil failures around 30,000 miles and the misfire codes didn't always point to the correct coil, as a result we were adopting a shotgun approach to coil failures and almost treating coils as a 30,000 mile service item.
I ended up with a pile of coils under the bench so rigged up a coil tester to sort good from bad. After stress testing half a dozen coils I realised the problem was the spark was tracking along the rubber boot to the metal body of the spark plug. After that I reverted to using a 10% narrower spark plug gap that been specified for the same engine type before the change to plug top coils. No change in performance or emissions but we had less problems with the coils.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I ended up with a pile of coils under the bench so rigged up a coil tester to sort good from bad. After stress testing half a dozen coils I realised the problem was the spark was tracking along the rubber boot to the metal body of the spark plug. After that I reverted to using a 10% narrower spark plug gap that been specified for the same engine type before the change to plug top coils. No change in performance or emissions but we had less problems with the coils.
Thats pretty interesting, I never would have thought of that.
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