IP timing device question

[Jake_Speed]

I was rebuilding my injection pump (92 N/A) today and was looking at the timing device area, and I noticed that there's no fuel supply hole on the side (back of pump) where the cold start/advance cover is. There is a hole on the opposite end of the housing, but I think this hole feeds back to the vane pump and therefore helps to pull the piston with negative pressure. On the piston itself there's a small orifice inside the cylindrical passage which opens to the main body of the pump right where the pin for the roller ring inserts, but if pressurised fuel passes through there from the main body into the cavity at the rear of the piston, then how does it make the piston move? That rear cavity seems to be a sealed dead end, so I don't see how there's a pressure differential. It seems like the pressure would just equalize on both sides of the orifice, and there would be no force applied to the end of the piston. Just trying to understand how this thing develops pressure to act against the spring.

It seems there could be alternatives here to the wax approach a la Hagar for achieving maximum advance - 1) re-calibrate the orifice by inserting a plug with a smaller hole, or 2) change the piston spring to one with lesser tension. (read elsewhere about colour coding of the springs).

I've read the Bosch technical instruction book online, but just says the "pressure control valve develops pressure" which is applied to the piston which moves against the spring. Does anyone know exactly how this works?

Jake

[hagar]

keep reading --- and hagar does know how it works.

The WAX job is for a more complex reason. ---BUT we can modify the timing system.

hagar.