Correctly setting the firing order is critical for engine performance when replacing spark plugs on your 1994 Ford Ranger 4.0L V6. This engine uses a waste-spark ignition system, distributing high voltage to paired cylinders. Follow these steps precisely:
1994 Ford Ranger 4.0L Firing Order
The firing sequence is 1-4-2-5-3-6. Cylinders are numbered:
- Front of engine (radiator side): Passenger bank = Cylinder 1, Driver bank = Cylinder 2
- Rear of engine (firewall side): Passenger bank = Cylinder 3, Driver bank = Cylinder 4
- Middle: Passenger bank = Cylinder 5, Driver bank = Cylinder 6
Spark Plug Replacement & Wiring
Critical steps:
- Label ignition wires before removal using masking tape (e.g., "Cyl 1," "Cyl 4").
- Remove wires one at a time to prevent cross-connection. Clean debris around plugs.
- Install new spark plugs gapped to 0.052-0.056 inches. Torque to 13-15 ft-lbs.
- Reconnect wires per firing order:
Ignition coil terminal pairing (waste-spark system):
- Terminal A: Cylinders 1 and 4
- Terminal B: Cylinders 2 and 5
- Terminal C: Cylinders 3 and 6
Verification & Testing
- Double-check wire routing against cylinder numbering. Ensure no crossed or loose connections.
- Start the engine: Smooth idle confirms correct installation. Misfires or hesitation indicate wiring errors.