Spark Plug 4955850/4937472/5473010 – Verified Fitment for Cummins

Verified Cross-Reference Coverage — Each plug variant mapped against Cummins gas engine control modules to prevent thread-length or electrode-gap mismatch on site.

Technical Specifications

Application Suitability

Why the Same Part Number Ships in Multiple Variants Across Cummins Gas Engines

A Spark Plug for Cummins ISB5.9G / QSL9 / L9N CM2380 cross reference fitment must account for control-module suffixes that change thread reach and gap tolerance.

Over years working around gas-powered construction and municipal fleets, I have watched crews pull a plug that "should" fit according to a generic cross-reference chart, only to find the thread bottoms out or the electrode sits too deep in the combustion chamber. The root cause is almost always a variant suffix on the engine plate that the chart ignores [NEED_CITE: Cummins gas engine spark plug variant identification practices]. A plug ordered for an ISB5.9G CM2180 may physically thread into an L9N CM2380 L124B, but the electrode position will be wrong, causing misfire under load. That single mismatched plug can idle a refuse truck or generator set while the team waits for the correct variant to arrive.

Fitment Range Across Cummins Gas Engine Generations

This Spark Plug for Cummins ISB5.9G / QSL9 / L9N CM2380 cross reference fitment spans engine families from the legacy C GAS PLUS CM556 through the current L9N CM2380 L124B. Each family uses a different combustion-chamber geometry, so the plug reach, heat range, and electrode material must match the specific control-module designation on the engine nameplate. Cross-referencing 4955850, 4937472, and 5473010 (for identification purposes) against the full engine model and serial range eliminates the guesswork that generic tables introduce.

Thread, Hex, and Electrode Verification Before Installation

The M14×1.25 thread pitch and 16mm hex size are consistent across all three reference numbers, but the installed depth and electrode projection vary by engine variant. When a worn or painted-over nameplate leaves only the engine model as a starting point, providing a photograph of the old plug beside a caliper or thread gauge allows the technical team to confirm reach and gap. A sample unit shipped ahead of a bulk order lets the workshop verify physical fitment on an actual cylinder head [NEED_CITE: spark plug thread engagement standards for natural gas engines]. This step prevents the situation where an entire fleet order arrives only to sit on the shelf because the thread length is off by a few millimeters.

How Electrode Material and Gap Tolerance Affect Ignition in Gas Engines

The iridium-tipped nickel alloy center electrode resists erosion from the higher combustion temperatures typical of stoichiometric natural gas operation. High-purity alumina ceramic insulation (95% Al₂O₃) maintains dielectric strength across repeated thermal cycles, reducing the risk of flashover along the insulator nose. The ±0.02 mm electrode gap tolerance ensures the spark energy concentrates at the intended point rather than dispersing, which matters especially under the elevated cylinder pressures of turbocharged gas engines like the QSL9 G CM558. The ISO 4287 Ra ≤ 0.8 μm surface finish on the shell reduces carbon adhesion, extending the interval between gap checks during routine service [NEED_CITE: iridium electrode wear characteristics in natural gas combustion].

The Hidden Cost of Installing a Variant-Mismatched Plug

Forcing a plug with incorrect thread reach can strip the cylinder head threads or leave the electrode recessed too far, leading to incomplete combustion and elevated exhaust temperatures. The machine may run at idle but misfire under load, which operators sometimes mistake for a fuel-system problem. By the time the real cause is diagnosed, the engine has accumulated hours of abnormal combustion, potentially damaging the catalytic converter downstream [NEED_CITE: misfire impact on catalytic converter lifespan in natural gas engines]. The cost of the wrong plug is minor; the cost of the diagnostic detour and the secondary component damage is not.

Why Buyers Source This Plug Through XUNPO

Own production on selected lines and qualified sourced supply carry the same quality-control and warranty terms under one account, so a mixed order of plugs, gaskets, and filters ships under a single warranty reference. Eight product categories mean the spark plugs travel in the same consignment as the ignition coils and seal kits the same repair job requires, avoiding split freight. Minimum order is one piece, which matters when a single machine is down and the fleet order is not yet justified. The Guangzhou warehouse holds stock on common variants for fast dispatch. Part identification works from a part number, a machine model, a photograph of the old plug, or a nameplate image. Cross-reference verification covers superseded and alternate numbers across all three reference designations.

Documentation & Verification

• Commercial invoice listing each plug variant by engine model and control module suffix
• Cross-reference sheet mapping 4955850, 4937472, 5473010 (reference only) to engine serial ranges
• Dimensional check record confirming thread length and gap before dispatch
• Warranty terms document covering manufacturing defects for 3–12 months
• Packing photographs showing plug packaging integrity and labeling accuracy
• HS code and customs documentation support for international gas-engine-parts shipments

Fitment Check Before Installation

• Compare thread length of the new plug against the removed unit using a thread gauge or caliper
• Verify the 16mm hex seats fully in the existing spark plug socket without interference from adjacent components
• Confirm electrode gap with a feeler gauge before installation, adjusting only within ±0.02 mm tolerance
• Hand-thread the M14×1.25 plug to detect cross-threading before applying torque
• If the old plug shows unusual electrode wear patterns, photograph and share for root-cause review

Inquiry Guidance for Accurate Fitment

Provide the full engine model and control module number from the nameplate — for example, ISB5.9G CM2180 or L9N CM2380 L124B — along with the engine serial number if available. If the nameplate is worn or painted over, send a photograph of the old plug beside a ruler or caliper so thread reach and hex size can be confirmed visually. For fleet orders across mixed engine models, share the complete unit list so variant-level cross-referencing covers every machine in one pass.

Frequently Asked Questions

Q: How do I confirm which of the three reference numbers fits my specific engine variant? A: Provide the full engine model and control module suffix from the nameplate, such as ISC8.3 G CM2180 C101. The technical team cross-references 4955850, 4937472, and 5473010 (reference only) against the engine serial range to identify the correct variant, including any superseded numbers that earlier catalogs may list differently.

Q: My old plug carries a number not found in current catalogs — is there a superseded replacement? A: Cummins has updated plug designations across gas engine generations. Share a photograph of the old plug and the engine plate. The cross-reference verification process covers superseded and alternate numbers, mapping the discontinued designation to the current equivalent that matches your engine's combustion-chamber geometry and control module.

Q: I only have the engine model, not the part number — can you still identify the correct plug? A: Yes. The engine model and serial number are sufficient to narrow down the correct variant within the C GAS PLUS, ISB5.9G, QSL9, or L9N family. A photograph of the existing plug helps confirm thread reach and electrode configuration when the nameplate alone leaves ambiguity between variants.

Q: Do different Cummins gas engine families use the same plug or different variants? A: Different families typically require different variants. The ISB5.9G CM2180 and the L9N CM2380 L124B, for example, differ in combustion-chamber depth and thermal profile, which changes the required thread reach and electrode material. Each family and control-module combination is verified individually before an order is confirmed.

Q: Can I get a sample to confirm fitment before ordering for the whole fleet? A: A sample unit is available for physical fitment confirmation on your actual cylinder head before you commit to a bulk order. This is particularly useful when servicing an unfamiliar engine build or when transitioning from a superseded plug number to its current replacement across a mixed fleet.