Cold Starting & Running
The injection pump timing advance piston is located in the bottom of the injection
Cold starting and running is improved by advancing the injection timing at idle and at low speed.
The cold start lever turns a cam which in turn pushes the timing advance piston to the left. This advances injection timing about 5°. Advancing the timing allows more time for the fuel to burn, thereby improving starting and running when cold.
The cold starting/cold running injection timing advance does not affect the entire
range of injection timing —
since above 2000 RPM the timing advance piston does not contact the cam.
Injection timing begins sooner (timing is advanced) to compensate for cold starting and cold running.
Above 2000 RPM (cold start advance lever pulled up), the timing advance piston does not contact the cam.
As engine speed increases, vane pump fuel pressure increases and pushes the timing advance piston to the left against the spring so that the roller housing shifts.
This means that the distributor plunger begins injection sooner (timing is advanced) to compensate for higher engine speeds.