You MUST find the firing order diagram on your engine. This is crucial for safety and proper engine function. It's usually stamped on a tag near the distributor or on the engine block itself. Some are even cast into the valve cover.
Here's what you need to do:
1. Find the Firing Order: Look for the sticker or casting on your engine. It will explicitly state the firing order (1-5-4-2-6-3-7-8 for the 5.0L) and likely show a diagram of the distributor cap with the corresponding cylinder numbers. This is the most reliable source.
2. Identify #1 Cylinder: Locate the number one spark plug. This is usually done by finding the timing marks on the harmonic balancer. You'll need to consult a repair manual or online resources for your specific engine to understand exactly how to do this.
3. Distributor Cap Orientation: Once you know #1 cylinder and the firing order, you can then match the rotor position to the #1 spark plug wire on the distributor cap. The rotor will point towards the terminal for #1 cylinder when the engine is at Top Dead Center (TDC) on the compression stroke of #1 cylinder. This step requires understanding of engine timing.
4. Wire the Distributor Cap: Follow the firing order (1-5-4-2-6-3-7-8) sequentially around the distributor cap, connecting each wire to the appropriate terminal.
Without the engine's specific distributor cap and the marking referencing the firing order, any attempt to provide a definitive wire placement will be risky and could lead to engine damage. A repair manual specific to your 1985 Ford Mustang 5.0L is strongly recommended. These manuals typically provide diagrams and detailed instructions for this procedure. If you are not comfortable with this task, taking it to a mechanic is the safest option.
