The 5.7 Hemi fires cylinders in this sequence: 1-8-4-3-6-5-7-2
The firing order is the sequence in which the engine's cylinders ignite fuel and produce power strokes. For the 5.7-liter Hemi engine, that sequence is 1-8-4-3-6-5-7-2. This order matters because it distributes power evenly across the crankshaft, keeps the engine balanced, and prevents vibration. If your ignition wires, spark plugs, or distributor cap are installed in the wrong order, the engine will misfire, run rough, or not start at all.
The Hemi engine uses a distributor cap (on older models) or coil-on-plug ignition (on newer ones) to send spark to each cylinder in the correct sequence. Cylinder 1 is always the front-most cylinder on the driver's side of the engine. From there, the firing order alternates between sides of the engine block in a pattern that keeps combustion balanced.
Key Takeaways
- The 5.7 Hemi firing order is 1-8-4-3-6-5-7-2, and this sequence must be followed when installing spark plug wires or replacing ignition components.
- Cylinder 1 is located at the front of the engine on the driver's side, and numbering continues down that side before crossing to the passenger side.
- Incorrect firing order causes misfires, rough idle, poor acceleration, and check engine lights that point to multiple cylinders at once.
- Distributor cap models and coil-on-plug systems both follow the same firing order, but the physical layout of spark plug wires differs between them.
How cylinder numbering works on the 5.7 Hemi
Cylinders are numbered from front to back, starting on the driver's side. On the 5.7 Hemi, cylinders 1, 2, 3, and 4 run down the left (driver's) side of the engine, and cylinders 5, 6, 7, and 8 run down the right (passenger) side. Cylinder 1 is always closest to the front of the vehicle, near the timing cover and crankshaft pulley.
When you look at the engine from the front, the driver's side is on your left. This matters because spark plug wires and coil packs are physically arranged around the engine in a way that matches the cylinder locations. If you remove a spark plug wire and do not mark where it came from, you can easily install it on the wrong cylinder and break the firing order.
Firing order for distributor cap models
Older 5.7 Hemi engines use a distributor cap with a rotor arm inside. The rotor spins and points to each terminal on the cap in sequence. The cap has eight terminals arranged in a circle, and spark plug wires connect from each terminal to its corresponding spark plug. The firing order 1-8-4-3-6-5-7-2 tells you the order in which the rotor touches each terminal as it rotates.
When you install spark plug wires on a distributor cap model, the wire from cylinder 1 goes to the terminal marked "1" on the cap. The next wire in the firing sequence (cylinder 8) goes to the terminal marked "8," and so on. If you install wires in the wrong order, the spark reaches the wrong cylinder at the wrong time, and the engine will not run. The rotor still spins at the correct speed, but it is now firing cylinders out of sequence.
Firing order for coil-on-plug ignition systems
Newer 5.7 Hemi engines use coil-on-plug ignition, where a small ignition coil sits directly on top of each spark plug. There is no distributor cap or rotor. Instead, the engine computer controls each coil individually and fires them in the correct sequence based on crankshaft position sensors. The firing order is still 1-8-4-3-6-5-7-2, but you do not see it physically laid out the way you do with a distributor cap.
If you replace spark plugs or ignition coils on a coil-on-plug system, you straightforward remove the coil from one cylinder and install it on the same cylinder. The computer handles the firing sequence automatically. However, if you accidentally swap coils between cylinders, the computer will still fire them in the correct order — the coils themselves are interchangeable. The real risk is swapping spark plugs between cylinders, which can cause a misfire if the plugs are different heat ranges or wear levels.
What happens when firing order is wrong
A wrong firing order causes the engine to misfire because spark reaches a cylinder at the wrong point in its combustion cycle. The piston may be on the exhaust stroke instead of the intake stroke, or the fuel may have already burned. The result is unburned fuel in the exhaust, a rough idle, hesitation during acceleration, and a check engine light.
The check engine light usually shows multiple cylinder misfire codes — for example, P0300 (random misfire), P0301 (cylinder 1 misfire), and P0308 (cylinder 8 misfire) all at once. This pattern tells you that the problem is not a bad spark plug or coil on one cylinder, but rather a timing or sequencing issue affecting multiple cylinders. If you recently replaced spark plug wires or worked on the ignition system, wrong firing order is the first thing to check.
How to verify the correct firing order during installation
Before you disconnect any spark plug wires, take a photo or write down which wire connects to which cylinder. Mark each wire with tape and a pen if the engine bay is crowded. Remove wires one at a time and install them in the correct sequence: 1-8-4-3-6-5-7-2.
If you are working from a service manual or online diagram, match the cylinder location on the engine to the terminal position on the distributor cap. The cap usually has the cylinders printed or embossed on it, but the numbers can be small or worn. Trace each wire from the spark plug back to the cap to confirm the connection. For coil-on-plug systems, straightforward note which coil sits on which cylinder before you remove anything, and reinstall each coil on the same cylinder.
After you finish, start the engine and listen for rough idle or hesitation. If the engine runs smoothly and the check engine light does not come on, the firing order is correct. If the light appears or the engine runs rough, stop when ready and recheck each wire or coil against the firing order sequence.
Common mistakes when working with spark plug wires
The most common mistake is removing all the spark plug wires at once and then trying to remember which one goes where. Even experienced mechanics mark each wire before removal. Another mistake is assuming the wires are arranged in numerical order around the engine — they are not. Cylinder 1 is at the front, but cylinder 2 is not next to it; the firing order jumps around the engine block.
A third mistake is installing wires on a cold engine and not starting it to check. Firing order problems do not always show up until the engine runs under load. A fourth mistake is confusing the firing order with the cylinder numbering. The cylinders are numbered 1 through 8, but they fire in the order 1-8-4-3-6-5-7-2. These are two different things, and mixing them up will cause you to install wires in the wrong sequence.
Frequently Asked Questions
Can I start the engine if one spark plug wire is in the wrong position?
The engine may start but will run very rough and misfire on that cylinder. You will hear a stuttering or popping sound, and the check engine light will come on. Do not drive the vehicle — stop and correct the wire position when ready. Running on a wrong firing order can damage the catalytic converter over time.
Does the 5.7 Hemi firing order change between Dodge, Jeep, and Ram vehicles?
No. All 5.7 Hemi engines use the same firing order: 1-8-4-3-6-5-7-2. The engine block is the same regardless of the vehicle it is installed in. The only difference is the physical layout of the engine bay, which may make it easier or harder to access the spark plugs, but the firing order itself never changes.
What is the difference between firing order and ignition timing?
Firing order is the sequence in which cylinders ignite — which one goes first, second, third, and so on. Ignition timing is when each spark occurs relative to the piston position in that cylinder. Both matter, but they are separate things. A wrong firing order means the cylinders ignite in the wrong sequence. Wrong ignition timing means they ignite at the right sequence but at the wrong moment in the combustion cycle.
If I have a coil-on-plug system, do I need to worry about firing order?
The engine computer handles firing order automatically, so you do not need to think about it during routine maintenance. However, if you are replacing the engine computer or crankshaft position sensors, firing order becomes relevant because the computer uses sensor signals to determine when to fire each coil. If sensors are installed incorrectly, the computer may fire cylinders out of sequence.
Where can I find a diagram showing the firing order on my specific engine?
The owner's manual for your vehicle usually includes a firing order diagram in the engine section. You can also find diagrams in factory service manuals, which are available through the vehicle manufacturer's website or through repair manual databases. The diagram shows cylinder locations and the sequence in which they fire, which is helpful if you are working on the engine for the first time.