Dakota 2WD V6-239 3.9L (1987)
Cruise Control Vacuum Reservoir: Testing and Inspection
1. Disconnect vacuum hose at servo, then connect a suitable vacuum gauge to hose.
2. Start engine, then note gauge reading at idle.
3. Gauge reading at idle should be approximately 10 inch Hg.
4. If vacuum reading is not as specified, check for leakage or poor engine performance.