Vacuum Pump: Description and Operation

Fig. 1 Vacuum pump installation. 4-135 (2.2L) diesel engine:

Fig. 2 Vacuum pump installation. 4-143 (2.3L) diesel engine:

Fig. 3 Vacuum pump installation. V8-420 (6.9L) engine. 1983---84 shown, 1985---87 similar:

On vehicles with diesel engines, insufficient vacuum is available to operate the vacuum booster brake. Vacuum is supplied from a vacuum pump located on the top right side or left front side of the engine, Figs. 1, 2, & 3. This pump is driven by a single belt off the alternator. These vehicles also incorporate a low-vacuum switch that actuates the brake warning light when vacuum is below a specified level. This switch senses vacuum through a fitting in the intake manifold that intercepts vacuum flow from the pump.