A hose connector that may not have been crimped tightly enough is the root of a Cummins recall that covers 39,052 L9 diesel engines. Cummins, Inc. told the National Highway Traffic Safety Administration on September 28, 2026 that the remote fuel filter hoses on the engines, part number D563027BX03, may separate from the fitting. The company says the result is a fuel leak and an engine stall.
The new filing is the fourth Cummins recall tied to the same hose, and it dwarfs the two earlier campaigns read for this article, which covered 230 and 715 engines. This one reaches almost 40,000, installed in buses, trucks, motorhomes and fire apparatus.
A Stage 2 hose that pulls off its fitting
Cummins describes a Stage 2 fuel filter hose that can pull off the fuel fitting, and in its Part 573 report gives the stated cause as possibly insufficient crimping of the connector, leaving too little hose retention. The consequence in NHTSA’s campaign record has two halves. A fuel leak near an ignition source raises the risk of fire, and an engine stall raises the risk of a crash.
The stall is the part that matters for the vehicles named in the buyer list. A transit bus or fire truck that loses fuel supply loses engine power, and Cummins states in the report that a disconnected hose will result in an engine stall, increasing the risk of a crash. The fire risk is conditional, as the company words it: a leak “may increase the risk of a fire” when an ignition source is present.
The report estimates that 3 percent of the engines have the defect. Applied to 39,052, that works out to roughly 1,170 engines by arithmetic, a figure the report does not state itself. The report lists no claims, incidents, injuries or fires, and describes the risks only as potential outcomes.
Thirteen buyers and a 2020 to 2026 build window
Cummins built the affected L9s from December 7, 2020 to April 10, 2026, according to engine build dates on the dataplates. Three part numbers are involved: 6316754, 6316757 and 6316899. The engines went into transit buses, trucks, recreational vehicles and fire trucks, and the report names the buyers: Big Rig, Battle Motors, Grove Worldwide, TEMSA, Tiffin Motorhomes, Shyft Group, Sutphen Corporation, NOVA Bus, Autocar LLC, New Flyer Industries, Gillig Corporation, DTNA and PACCAR.
Because the recall is filed under equipment rules, NHTSA’s record lists the make as Cummins, the model as L9 and the model year as 9999, a placeholder.
Three recalls that came before it
The hose has been recalled before. Cummins’ June 2024 report for recall 24E038 covered 230 engines built between November 7, 2022 and March 29, 2023, with an estimated 100 percent affected. Cummins first heard of fuel leaks on March 27, 2024 from an OEM, Nova Bus; a warranty search found 15 claims, and on May 14, 2024 its Product Safety Defect Board decided to conduct a safety campaign. The report says no fires, accidents or injuries had been reported.
NHTSA’s record for recall 25E004, received January 17, 2025, adds 715 engines with the same part number and the same description, with owner letters mailed on March 11, 2025. The 2024 campaign’s remedy hoses carry date code 230310 or later, and the 2024 report says the condition was corrected in production on April 1, 2023. A third campaign, 23E055, is cited in the new report but was not read for this article.
The new filing turns on what happened to the remedy hoses. After a fuel hose redesign in April 2026, Cummins evaluated the earlier hose designs that had been used as remedy parts, between June 1 and September 4, 2026, and on September 22 decided to replace the hoses on the whole affected population. New builds stopped using the suspect hoses on April 11, 2026.
Replacement hoses and the November 20 letters
Dealers will replace the fuel hoses at no charge with parts that use an updated hose-to-fitting crimp design. The replacement part numbers are 6552994, 6553001 and 6553018. Engines already repaired under recalls 23E055, 24E038 or 25E004 need the redesigned parts as well. Owner letters are expected on November 20, 2026, Cummins’ recall number is C7311, and customer service can be reached at 1-800-286-6467. The report’s planned dealer-notification and end dates carry an apparent typographical error in the year, so the November 20 owner date is the one the NHTSA record states cleanly. The report classes the remedy as a replacement, with no inspection-only option.
The sequence leaves a pointed fact on the record: the 2024 campaign installed hoses with an improved connector crimp as its fix, and the 2026 campaign replaces those same remedy designs with a newer crimp. The filing list carries the Cummins campaign as received September 28, 2026, ahead of the October 2 filings from Roadmaster, Mercedes-Benz and Blue Bird.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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