2017 Volvo VNL Spark Plug Type & Gap

Quick reference

Why the right plug matters

While spark plugs might seem like minor components, they play a critical role in your engine's performance and longevity. For the 2017 Volvo VNL, especially those equipped with the Cummins ISX12 G natural gas engine, selecting the correct spark plug is paramount. The "right plug" is a careful balance of heat range, electrode materials, and design, all optimized for your specific engine.

• Heat Range: This refers to the plug's ability to dissipate heat from the combustion chamber. A plug that's too "cold" (dissipates heat too quickly) can lead to fouling, while one that's too "hot" (retains too much heat) can cause pre-ignition and engine damage. Natural gas engines operate at higher combustion temperatures than gasoline or diesel engines, requiring specific heat ranges to ensure optimal performance and prevent premature wear.

• Electrode Metal: Spark plugs primarily come in copper, platinum, and iridium. Given the demanding conditions of a natural gas engine, iridium plugs are almost exclusively recommended. Iridium is incredibly strong and has a very high melting point, allowing for fine-wire electrodes that provide a more consistent and powerful spark over a longer lifespan. Platinum offers similar benefits but generally isn't as durable as iridium in extreme applications. Copper plugs, while excellent conductors, have a much shorter lifespan and would not be suitable for the extended service intervals and operating conditions of a commercial natural gas engine.

How to gap a spark plug

While many premium iridium spark plugs come pre-gapped, it's always a good practice to verify the gap before installation, especially for natural gas applications where precise gaps are crucial. For the Cummins ISX12 G, the recommended gap is 0.028-0.032 inches (0.7-0.8 mm).

1. Use the correct tool: A wire-type spark plug gapping tool is preferred for iridium plugs. Feeler gauges can damage the fine-wire electrode.
2. Check the gap: Slide the appropriate wire gauge between the center and ground electrodes. There should be a slight drag.
3. Adjust (if necessary): If the gap is too small, carefully bend the ground electrode outwards using the gapping tool's adjustment notch. If the gap is too large, gently tap the ground electrode on a clean, hard surface to close it incrementally. Never pry or bend the center electrode, as this can damage the iridium tip.

Replacement procedure tips

Replacing spark plugs on a commercial natural gas engine like the Cummins ISX12 G in a 2017 Volvo VNL requires careful attention to detail. This engine uses a coil-on-plug (COP) ignition system.

• Coil-on-plug removal: Each spark plug has its own ignition coil mounted directly above it. To access the spark plugs, you'll need to carefully disconnect the electrical connector from each coil and then unbolt and remove the coil. Be gentle with the connectors and retainers, as they can become brittle over time.

• Anti-seize debate: For spark plugs going into aluminum cylinder heads, using a small amount of anti-seize compound on the plug threads has been a long-standing practice. However, many modern spark plugs have a special coating that acts as an anti-seize agent. Consult the spark plug manufacturer's recommendations. If you choose to use it, apply a very thin layer only to the threads, avoiding the electrode. Be aware that anti-seize can affect torque readings, so it's vital to reduce the specified torque by about 10-20% if using it to prevent overtightening.

• Dielectric grease on boots: Apply a thin layer of dielectric grease inside the spark plug boot (the portion that connects to the top of the spark plug). This helps to seal out moisture, prevents sticking, and makes future removal easier, while also ensuring good electrical insulation.

Known issues

For the 2017 Volvo VNL with the Cummins ISX12 G natural gas engine, there aren't widespread "known issues" specifically related to spark plug breakage like the Ford 5.4L 3V engines had. However, it's crucial to adhere to the recommended service intervals and use high-quality, OEM-specified spark plugs to prevent common problems such as:

• Premature wear: Using incorrect heat range or lower-quality plugs can lead to rapid electrode wear, misfires, and reduced fuel efficiency.
• Fouling: Rich fuel mixtures or oil intrusion can lead to carbon or oil deposits on the spark plug, causing misfires. Proper engine maintenance is key to preventing this.
• Cross-threading: Always start threading new spark plugs by hand to ensure they're properly seated before using a wrench. Cross-threading can severely damage the cylinder head threads.

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