The firing order for the 4.9L inline-6 is always 1-5-3-6-2-4.
To find the correct placement, you must do one of the following:
1. Consult your owner's manual: This is the most reliable method. The manual will have a diagram showing the correct wire placement on the distributor cap for your specific vehicle.
2. Look at the distributor cap itself: Some distributor caps have the firing order stamped or molded into the cap itself.
3. Use a reliable online resource: Websites specializing in Ford parts or repair manuals might have diagrams, but verify the information is accurate for your specific year and engine code (found on an engine ID tag).
4. Mark the wires before removal: If you removed the wires before needing to reattach them, the best method is to carefully mark the old positions to guarantee correct replacement.
Caution: Incorrectly placing the spark plug wires can result in misfires, poor engine performance, and potentially damage the engine. If you're unsure, seek professional help from a mechanic.