The RIV timing light is a M/B tool that allows you to install a probe in the side of the IP. The probe senses the notch in the rotating shaft in the IP. When you are nowhere near the notch, no lights are lit. When you approach the notch, the "A" light illuminated. When you are dead on the notch, both "A" and "B" illuminate. When you pass the notch, ever so slightly, the "A" light goes out. The spec for the engine when you use this tool is 15°ATDC. Not all engines have the capability to use this tool. The older 616 and 617 engines did not have the port in the side of the IP. The '80 vehicle would probably not be able to use the RIV tool.

You can certainly search "timing" and "injection pump" and read for hours. Also check out the DIY section where the most relevant posts are indicated by section.

If your mechanic gets the pulse timing tool, the spec would not be 15°ATDC but would be 13.5°BTDC which is the correlation that we established on the SD.