The firing order itself is 1-5-4-8-6-3-7-2. However, this isn't directly related to wire placement on a cap since there isn't one. The order refers to the firing sequence of the cylinders. To determine the correct wire routing, you'll need to consult a wiring diagram specific to your 1989 Ford 7.5L engine. This diagram should be found in a repair manual or online resources. Trying to determine it by any other means is unreliable and risks engine damage.
