Duramax 6.6 Firing Order – With Diagrams!

(Last Updated On: November 17, 2023)

When it comes to diesel engines, the Duramax 6.6 is a popular choice for truck enthusiasts. One important aspect of this engine is its firing order, which refers to the sequence in which the cylinders fire. Getting the firing order right is critical for the engine to function properly and efficiently.

The firing order for the Duramax 6.6 is 1-2-7-8-4-5-6-3. This sequence determines the order in which fuel is injected and ignited in the cylinders. 

Remember that this firing order is specific to the Duramax 6.6 engine and should not be confused with other engines.

Duramax 6.6L Firing Order Diagram

standard drama 6.6L firing order

Stock Duramax 6.6 Firing Order

As an expert in diesel engines, I can confidently say that understanding the firing order of a Duramax 6.6 engine is crucial for proper maintenance and troubleshooting. The firing order for a stock 6.6-liter Duramax diesel is 1-2-7-8-4-5-6-3. This means that the first cylinder to fire is number one, followed by cylinders two, seven, eight, four, five, six, and three in that order.

The cylinders on a Duramax engine are numbered from front to back, starting with the number one cylinder. The number one cylinder on an inline Duramax engine is located close to the timing cover at the front side of the engine.

If the engine is left completely stock, there isn’t much of a problem with this firing order. However, the crankshaft on the 6.6-liter Duramax is known for being on the weaker side. This means that if you plan on upgrading your engine with performance parts, you may need to consider upgrading your crankshaft as well to handle the increased power.

It is also important to note that a misfire in any of the cylinders can cause a variety of issues, including decreased engine performance, reduced fuel efficiency, and increased emissions. If you are experiencing any of these issues, it is important to diagnose and fix the problem as soon as possible to avoid further damage to your engine.

6.6 Firing Order Sequence

As a diesel engine, the Duramax 6.6 has a specific firing order sequence that determines the order in which fuel is injected and ignited in each cylinder. The firing order sequence for the Duramax 6.6 is 1-2-7-8-4-5-6-3.

Using the wrong firing order sequence can cause engine damage and poor performance.

This sequence is important because it ensures that the engine fires in the correct sequence and prevents damage. The sequence controls the timing of the fuel injection and ignition events.

To help remember the firing order sequence, you can use the acronym “I Have Very Little Faith In My Engine.” Each letter corresponds to a cylinder in the firing order sequence.


Remembering the firing order sequence can be especially important when performing maintenance tasks such as changing spark plugs or replacing fuel injectors. By following the correct sequence, you can ensure that your engine runs smoothly and efficiently.

Alternative 6.6 Duramax Firing Order

While the stock firing order works well for most applications, it can cause issues when the engine is modified for higher performance. In the 6.6-liter Duramax, it has a reputation for its crankshaft being on the weaker side. As a result, increasing the power output can put additional stress on it.

One way to address this issue is to modify the firing order.

By changing the firing order, it is possible to relieve stress on the front portion of the crankshaft in higher performance applications.

For example, the new camshaft design changes the firing order to 1-5-6-3-4-2-7-8. This change can help to improve engine performance and reliability.

Alternative Diagram

Frequently Asked Questions

What are the cylinder numbers for a 2015 Duramax?

The Duramax cylinder numbers are 8 in total. The 2, 4, 6, and 8 cylinders of the Duramax are placed on the driver’s side, while the 1, 3, 5, and 7 cylinder numbers are placed on the passenger’s side. This cylinder numbering is important to remember when diagnosing engine problems or doing any maintenance on your Duramax engine.

What is the cylinder layout for a Duramax L5P?

The Duramax L5P has a V8 engine configuration, with each bank of cylinders having four cylinders. The cylinders are arranged in a V shape, with the cylinders tilted at an angle of 90 degrees. The L5P engine has a bore size of 4.06 inches and a stroke of 3.90 inches, resulting in a total displacement of 6.6 liters.

Which cylinder is number 2 on a Duramax?

The number 2 cylinder on a Duramax engine is located on the driver’s side of the engine. It is the second cylinder from the front of the engine on the driver’s side. This cylinder numbering is important to remember when diagnosing engine problems or doing any maintenance on your Duramax engine.

Why do LMM cranks break?

The LMM Duramax engine is known for crankshaft failures due to the high stresses placed on the crankshaft by the engine’s power output. The factory crankshaft is known to be weaker than aftermarket options, and the engine’s harmonic vibrations can cause the crankshaft to fail prematurely. Upgrading to a stronger aftermarket crankshaft is recommended for those looking to increase the power output of their LMM Duramax engine.


  • Randy Worner

    My name is Randy Worner and I am the founder of chevygeek.com. I have been working on cars and trucks for almost 45 years. For the last 36 years I have taught Automotive / Diesel Technology classes for UTI, Snap On Tools, Chrysler, Pepboys, Lone Star College, NAPA and TBC Corporation.I also own a technical writing company known as Supreme Technical Services. It is ASE Gold Seal certified and Blue Seal Certified Author of auto/truck repair information.

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