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How to Use a Timing Light on a 91 Jeep

Ignition timing is vital to optimum engine performance. Over-advanced ignition timing causes premature ignition. Premature ignition is also known as "ping" or "spark knock" and can damage internal engine components. Pistons may become pitted or fractured by premature ignition. Retarded timing will pollute the engine crankcase with wasted fuel and may over-heat the engine. Fuel economy suffers in either instance and engine longevity is diminished. Timing lights provide an accurate indication allowing precise adjustment.

Instructions

Timing Checks and Adjustments

1

Park the Jeep on level ground. Place it in park if it has an automatic transmission or neutral if it has a manual transmissions. Set the parking brake and block the wheels from movement with chocks or similar devices. Open the hood and attach the timing light leads, or wires according to the light manufacturers instructions. Consult the emission control information label for specifications. It is affixed to the firewall on the passenger side. Attempt no adjustment if none is recommended.

2

Highlight the timing mark on the crank pulley with white chalk. Locate and clean the numbered scale attached to the engine timing cover, just above the crank pulley. Make any disconnections specified on the emission control information label and start the engine. Allow the engine to reach operating temperature and normal idle speed.

3

Assure idle speed is in range of specifications before adjusting ignition timing. Aim the timing light at the scale above the crank pulley, taking care to avoid moving parts.The crank pulley mark will appear stationary due to the stroboscopic effect created by the timing light. Observe the pulleys mark position on the scale and compare it to the value specified on the emission control information label. No adjustment is necessary if the mark and specification match.

4

Make any needed adjustment by slightly loosening the distributor hold-down screw. Turn the distributor until the crank pulley mark aligns with the scales specified position. Use the timing light to observe position adjustment. Tighten the hold-down screw and turn off the engine. Restore any connections and remove the timing light. Test-drive the Jeep to evaluate any changes made.

Posted by Unknown at 12:15 AM

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