Since the air crossover and intake manifold in a diesel engine is unrestricted (unlike a gasoline engine which has throttle plates creating a venturi effect) there is no vacuum source. To provide vacuum, a vacuum pump is mounted in the location occupied by the distributor in a gasoline engine. This pump supplies vacuum for the EGR valve system, air conditioning servos, the cruise control servos, and the transmission vacuum modulator, where required.
The pump is a diaphragm type pump which needs no maintenance. It is driven by a drive gear on its lower end which meshes with gear teeth on the end of the engine camshaft.
REMOVAL & INSTALLATION
- Remove the air cleaner.
- Remove the vacuum hose from the pump outlet.
- Remove the air cleaner, and cover the intake manifold.
- Remove the vacuum pump clamp and bolt and then remove the pump.
- Install a new gasket.
- Install the pump assembly making sure that the drive gear meshes with camshaft gear.
- Rotate the pump so the inlet tube faces the front of the engine. The pump should be on a 20 degree angle.
- Tighten bolt and bracket to 20 ft. lbs.(27 Nm).
- Connect the vacuum hose to the pump outlet.
- Install the air cleaner.