Vacuum Pump

DESCRIPTION





Fig. 7

The vacuum pump and the power steering pump are combined into a single assembly on diesel engine models (Fig. 7). Both pumps are operated by a drive gear attached to the vacuum pump shaft. The shaft gear is driven by the camshaft gear.
The vacuum pump is a constant displacement, vane-type pump. Vacuum is generated by four vanes mounted in the pump rotor. The rotor is located in the pump housing and is pressed onto the pump shaft.
The vacuum and steering pumps are operated by a single drive gear pressed onto the vacuum pump shaft. The drive gear is operated by the engine camshaft gear.
The vacuum and power steering pump shafts are connected by a coupling. Each pump shaft has an adapter with drive lugs that engage in the coupling.
The vacuum pump rotating components are lubricated by engine oil. Lubricating oil is supplied to the pump through an oil line at the underside of the pump housing.
The complete assembly must be removed in order to service either pump. However, the power steering pump can be removed and serviced separately when necessary.
The vacuum pump is not a serviceable component. If diagnosis indicates a pump malfunction, the pump must be replaced as an assembly. Do not disassemble or attempt to repair the pump.
The combined vacuum and steering pump assembly must be removed for access to either pump. However, the vacuum pump can be removed without having to disassemble the power steering pump.
If the power steering pump requires service, simply remove the assembly and separate the two pumps.


OPERATION
Vacuum pump output is transmitted to the HEVAC, speed control, systems through a supply hose. The hose is connected to an outlet port on the pump housing and uses an in-line check valve to retain system vacuum when vehicle is not running.
Pump output ranges from a minimum of 8.5 to 25 inches vacuum.
The pump rotor and vanes are rotated by the pump drive gear. The drive gear is operated by the camshaft gear.