How are ignition timing issues diagnosed?
Diagnosing incorrect ignition timing for a distributor type engine is simple, and only requires a timing light. The timing light is connected to the number one cylinder spark plug wire and the battery terminals. Then, with the engine running, the pulsing of the ignition wire on the number one cylinder will cause the ignition timing light to flash. When the light flashes on the crankshaft pulley or harmonic balancer, the light will illuminate a line or arrow that corresponds to a gauge on the timing cover. This will allow the technician to identify where the timing is currently, and adjust the timing if needed.
How is Ignition Timing adjusted?
Ignition timing adjustments require the timing light to remain connected, the engine running, and the distributor hold-down fasteners to be loosened very slightly. Once the engine is warm, the distributor will be slowly rotated to achieve the exact angle of ignition in relation to the crankshaft pulley, and the hold-down fasteners will be tightened once again.
RepairPal Recommendations for Ignition Timing Adjustments
We do not recommend adjusting timing by vacuum pressure, by ear, or by idle speed. Vacuum pressure can be incorrect even if timing is correct, and idle speed is set after timing is corrected. Using these methods will result in an engine running below optimal efficiency, and the engine temperature may be too high or low in older engines.
What to look out for when dealing with incorrect ignition timing
When adjusting ignition timing on distributor type ignition system, there is a high probability of electric shock due to worn ignition wires or distributor cap. The wires should be inspected for wear and tear before attempting to rotate the distributor to adjust timing. Also, the vacuum or mechanical advance should be tested before adjusting timing, as these will prevent the distributor from maintaining proper timing.