Vacuum Advance Correction: Testing
- Disconnect hose from vacuum advance mechanism on distributor and connect a vacuum gauge. With engine idling at normal operating temperature, vacuum should be low. As engine speed is increased, vacuum should increase.
- Disconnect electrical lead from oil thermal switch (right side of oil pan). Connect lead to ground. No vacuum should be present on vacuum gauge. Ignition timing should advance to 9° BTDC. Reconnect oil thermal switch wire.
- On air conditioned vehicles, turn on air conditioning so compressor operates. Gauge should indicate more than 12 in. Hg vacuum.
- If system operates as described, reconnect advance hose. If not operating properly, check oil thermal switch. When temperature is below 59°F (15°C), switch should have continuity between terminal and ground. Above that temperature, there should be no continuity.
- If system still does not operate properly, check electrical connections to switching relay and distributor.
Courtesy of AMERICAN MOTORS/RENAULT CORP.