I'm not familiar with those methods, but... an interesting read

The coil inside the plug generates a tinyvoltage when heated by the burning diesel, so there is a kind of temperature sensor in the prechamber which is (according to the writer on the MB forums) usable to prime the pump.
Thinking furher: higher voltage = hotter burn = more power = better mileage (last 2 applyafter good priming too)
But I think the method is not very constant and needs base/top/bottom measurements every time you check the timing.
I'm going to check this method when my 1.9 runs again
