Vacuum Regulator Test - Cruise Master

Vacuum regulators are used on diesel engines only. Because of lower operating vacuum of diesel engines, cruise control system could become inoperative with just a very small vacuum leak.
1. Remove hose from transducer at regulator.
2. Attach vacuum gauge to regulator valve and start engine.
3. Vacuum should read between 6 and 7 inches Hg. If reading is below 6 or above 8, replace regulator valve.