The tool I referred to earlier is for quickly confirming activation of electronic fuel injectors.
Waekon 76462 EFI Quick Probe (Orange Probe) It might be too sensitive to use with a diesel although I'm sure a desperate and / or creative guy could devise a method to reduce sound transmission to the unit.
I've used a Snap-On MT257 with success on GM 6.2/6.5 liter diesels when I worked at a Chevrolet dealership. This tool is another type of pulse adapter for a timing light. I was in truck country back then and there were plenty of these engines around so I could come up with a good baseline for setting / checking timing. Occasionally a used one can be found for sale on the internet.
If the engine is set up with correct timing using the mechanical setting then checking with a light for maintenance only requires an initial check and subsequent re-checks as desired. The only need to determine the exact difference between mechanical specification and the measurement by the light is for 1) motorsports and racing, 2) comparison with others, or 3) because you enjoy hunting down that type of minutia. Otherwise, the initial measurements will serve, IME, as a perfect tool for future checks. Engine temperature, pop pressure variations, and injection pump condition all affect the timing result obtained so it seems as though "within a degree or two" became the acceptable standard for using the inductive light with adapter. IMO you're better served looking for fuel with consistent quality.