Cummins has recalled 39,052 L9 diesel engines because a pair of fuel hoses outside the engine block can pull off their fittings. The engines power transit buses, trucks, recreational vehicles and fire trucks, and the company has now been back to this same hose repeatedly since 2023.
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What makes this campaign unusual is that it replaces the fix as well as the original part. Engines that already went through earlier recalls have to be reworked again.
A hose that comes off the fitting
The filing is NHTSA equipment campaign 26E066000, reported by Cummins on September 28, 2026 for L9 engines under part number D563027BX03. Cummins states the defect directly: the remote fuel filter hoses may separate from the fitting. The consequence field spells out both risks. A fuel leak in the presence of an ignition source increases the risk of a fire, and an engine stall increases the risk of a crash.
In its detailed defect report, Cummins narrows the hardware. The hoses serve the remote Stage 2 fuel filter option, in which the filter sits away from the engine and fuel travels through a hose to reach it. Engines built between December 7, 2020 and April 10, 2026 are involved, Cummins estimates that about 3 percent carry the defect, and the root cause named is insufficient crimping at the connector, which may not retain the hose adequately.
The engine went to a long list of manufacturers, including NOVA Bus, New Flyer, Gillig, Autocar, Daimler Truck North America, PACCAR, Shyft Group, Sutphen and Tiffin Motorhomes. That spread is why the fleet is so mixed: a single hose design ended up under city buses, under fire apparatus and in motorhomes.
The failure as a driver meets it on the road
A separated hose does two things at once. It stops delivering diesel to the filter, so the engine can starve and stall, and it lets fuel escape wherever the hose is routed. Cummins notes that people may see or smell fuel leaking, and the malfunction indicator lamp may illuminate with low fuel pressure code FC559. For a loaded transit bus or a fire truck responding to a call, a stall under power is the more immediate danger, while a pool of diesel near a hot component is the fire scenario.
The report does not state a number of field reports or complaints, and it does not claim injuries or fires. The count in the record is the 39,052 engines that could be affected, not a tally of failures. At the estimated 3 percent defect rate, roughly 1,170 engines would actually carry a poorly crimped hose, but the company is replacing hoses on all of them because the filing treats the whole population as needing the redesigned parts.
The earlier and smaller campaigns give a sense of what an operator sees when it goes wrong. The 2024 filing lists visible smoke or other signs of a leak and a diesel odor as the warning signs, and the 2023 filing describes leaks first reported by PACCAR during vehicle assembly, which means some of the early failures were caught before the engines ever left a factory floor.
The fourth pass at the same hose
The history is the heart of the story. Recall 23E055 covered 1,135 L9 engines built between November 22, 2022 and February 28, 2023. Cummins first suspected insufficient crimping, introduced improved-crimp hoses on March 3, 2023, and then found leaks continuing. It traced them to hoses that had snagged on an assembly pallet and been damaged without notice, and it added hose-routing controls on May 14, 2023. The remedy hoses carried a date code of 230310 or later.
Recall 24E038 followed for about 230 engines destined for transit bus and recreational vehicle makers, and this time the filing blamed insufficient crimping of the connector outright. The record for the current campaign also names a third earlier recall, 25E004. After a redesigned hose entered production in April 2026, Cummins evaluated the hoses it had itself supplied as remedy parts in those campaigns, and decided to replace the hoses across the affected population. New builds stopped using the suspect hoses on April 11, 2026.
The practical result is a rare instruction. Engines remedied under 23E055, 24E038 or 25E004 need the redesigned parts installed, which means an owner who had a fix done in an earlier year is not finished. The replacement hoses carry the part numbers 6552994, 6553001 and 6553018, with an updated hose-to-fitting crimp.
Free replacement and the November mailing
Dealers will replace the fuel hoses at no charge. NHTSA’s letter to Cummins, dated September 30, 2026, shows owner notification letters expected to be mailed November 20, 2026, and the company’s report plans no interim owner notice. Owners can reach Cummins customer service at 1-800-286-6467 and cite Cummins recall number C7311. Until the engines are remedied, the letter notes, the affected units may not be sold. The record names no interim driving restriction and no reimbursement detail, so the campaign works the way a standard dealer recall does, with the letter as the trigger for the visit.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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