Regulated pressure produced by a vane supply pump in both fuel injection pumps is used to advance the timing
as the engine speed increases. A return spring is used to retard the timing as the engine speed is reduced. If a
spring should break, the timing will go to the advance position resulting in torque loss, a fuel knock and possible
engine overheating.
Retarded (late) timing will result in torque loss, high fuel consumption and white to black smoke.
The Lucas CAV D PA/D PS advance timing mechanism uses a check ball in the circuit which, if omitted during
assembly, will result in no timing advance. If the fuel injection pump has been replaced or the mechanism has
been removed to fix a leak, the problem can be that the check ball is missing.
