we have been kicking the diesel angle around in this thread
Diesel instrumentation - Page 4 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com
In fact i put together a prototype for a timing trigger yesterday, you might need to attenuate the signal a bit with a couple Meg pot until you just have one flash for each injection pulse.
Parts: 2 used GM knock sensors, one 1/4" FPT x 1/4" FPT pipe coupling.
Tools: a drill bit the size of my injection line, a 1/4" pipe tap, hack saw or dremel.
Procedure: drill a hole in the center of the coupling, thread the coupling deeper on both ends until the knock sensors will reach in to the hole, cut one side of the coupling out until it will fit over the injection line.
Place coupling on a straight section of the injector line.
Hand tighten the knock sensors until they clamp on the injection. Wire the sensors in parallel. Attenuate signal as needed. see pic