Spark Control System: Testing

1983 Renault LeCar 4D HatchbackSECTION Testing
  1. 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.
  2. 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.
  3. On air conditioned vehicles, turn on air conditioning so compressor operates. Gauge should indicate more than 12 in. Hg vacuum.
  4. 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.
  5. If system still does not operate properly, check electrical connections to switching relay and distributor.
Fig 1: Vacuum Advance Correction System
G41482
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.