2022 International MV Spark Plug Specs: Type, Gap & Torque

The 2022 International MV is a medium-duty workhorse known for its durability and versatility. While the majority of these trucks roll off the assembly line equipped with diesel engines (which use glow plugs or intake heaters rather than spark plugs), fleets opting for alternative fuels often utilize the Cummins L9N Natural Gas engine. Because compressed natural gas (CNG) and liquefied natural gas (LNG) engines are spark-ignited, proper spark plug maintenance is absolutely critical to prevent misfires, poor fuel economy, and costly downtime.

As an ASE-certified master technician, I've seen firsthand how ignoring the ignition system on these heavy-duty natural gas engines can leave a truck stranded. Here is everything you need to know about the spark plugs in a spark-ignited 2022 International MV.

Quick reference

Note: Diesel variants (Cummins B6.7 or L9) are compression-ignition and do not use spark plugs.

Why the right plug matters

Natural gas burns significantly hotter and slower than gasoline, placing immense thermal and electrical stress on the ignition system. Because of this, standard copper or platinum plugs will not survive long in an L9N block.

The OEM and recommended aftermarket plugs for these engines feature Iridium center electrodes. Iridium is much harder and more heat-resistant than platinum or copper, allowing the electrode to remain sharp and maintain a precise arc over thousands of operating hours. Using the exact heat range specified by Cummins ensures the plug tip stays hot enough to burn off carbon deposits, but cool enough to prevent pre-ignition and catastrophic piston damage under heavy towing loads.

How to gap a spark plug

Even if your iridium spark plugs claim to be "pre-gapped" out of the box, you must verify the gap before installation—especially with the incredibly tight 0.015" specification on the L9N engine.

1. Use the right tool: Always use a wire-style feeler gauge rather than a cheap coin-style ramp gauge. The delicate iridium center electrode can easily snap if scraped by a heavy tool.
2. Measure carefully: Gently pass the 0.015" wire through the gap. It should pass through with a slight drag.
3. Adjusting the gap: If the gap is too tight or too loose, use the bending tool on your gapper to physically bend the ground strap. Never pry against the center electrode or the porcelain insulator. Bend it slightly, re-measure, and repeat until perfect.

Replacement procedure tips

Replacing spark plugs on a commercial medium-duty chassis like the International MV requires attention to detail.

• Coil-on-Plug Handling: The L9N uses a coil-on-plug (COP) ignition system. When removing the coils, twist the boots gently before pulling up to break the seal. If a boot is stuck, use a specialized boot puller to avoid tearing the silicone.
• The Anti-Seize Debate: Cummins generally recommends installing spark plugs dry to ensure proper torque values. Adding anti-seize acts as a lubricant, which often leads to over-torquing, stretching the plug threads, or altering the plug's heat transfer to the cylinder head.
• Dielectric Grease: Always apply a small dab of dielectric grease to the inside of the spark plug boot before reinstallation. This prevents moisture intrusion, stops high-voltage tracking (arcing down the side of the plug), and makes future removal much easier.

Known issues

While you don't have to worry about the notorious broken plug shells found on early 2000s Ford 3-valve engines, the Cummins L9N does have its own quirks. Because of the extremely high cylinder pressures and voltages required to ignite natural gas, coil boots degrade faster than on standard gasoline engines.

If a truck comes in with a misfire code under load, always inspect the spark plug porcelain for faint black vertical lines (carbon tracking). This indicates the spark is blowing past the plug and arcing into the engine block. If you find carbon tracking, you must replace both the spark plug and the coil boot simultaneously; otherwise, the misfire will immediately return.

Need plugs replaced? Find a shop on Repairius.