Operation

Fig. 11 Cut Away View of the Manifold Pressure Compensator Mounted on the Injection Pump:

At low engine speeds, turbocharger pressure is insufficient to compress the spring and the diaphragm remains in its initial position. Once pressure reaches a certain level, the diaphragm and sliding pin begin to move downward against spring pressure. In turn, in a pattern determined by the conical control surface, the guide pin is moved and the stop lever pivots around M1, Fig. 11.
Because of tension from the governor spring, the tensioning and stop levers, guide pin, and control cone are effectively bound together; the tensioning lever therefore follows the stop lever's movement. Starting and tensioning lever rotate around their common pivot and move the control collar in the direction of greater pump delivery. Thus fuel delivery is increased in response to the greater air mass.
When turbocharger pressure falls, the spring under the LDA moves the sliding pin back upward, compensation action is reversed and fuel delivery is reduced accordingly. Should the turbocharger fail, the LDA assume its initial position and the engine operates normally, without smoke. Full-load fuel delivery is adjusted by the full-load stop screw in the governor cover.