Usage:
D379, D398, D399 Engines
Three methods are currently used to time the fuel injection on the above engines. The three methods are "Pin Timing", "Flow Timing" and use of the "6V3100 Engine Timing Indicator Group".
On a new, correctly adjusted engine, or an engine with new unit fuel pumps, the pin timing method is the easiest to use and gives excellent results. On a used engine, the pin timing method can not make an allowance for wear to the fuel pump plunger or any wear (erosion) to the inlet port of the fuel pump body. Either of these conditions will change the fuel flow timing.
Both the flow timing method (as described in the Service Manual) and the use of the 6V3100 Engine Timing Indicator Group can measure the wear on used engines so allowances can be made in the pin timing.
The use of the 6V3100 Engine Timing Indicator Group will deliver the most accurate measure of fuel injection timing and is the preferred method. The second choice is flow timing, and the third choice is pin timing.