Hi,
OPs image;
What is the yellow signal
How many cylinder diesel?
2 stroke or 4 stroke?
So the start of, or the end of, the double pulses indicates Cylinder 1, TopDeadCentre?
If the engine is 4 cylinder then from your blue trace the last of the pair will represent No1 Cyl TDC.
What is the amplitude of the pulses?
Your biggest problem is the fact that the pulse width and intervals will not be constant , but change with speed.
Tom... 