MX-13 Diesel Engine in Certain Kenworth, Peterbilt Trucks Plagued by Fuel Injector Defect, Lawsuit Says

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A proposed class action alleges the MX-13 diesel engine found in certain Kenworth and Peterbilt commercial trucks is plagued by a defect that can cause the fuel injector to partially or completely clog without warning and prevent fuel from reaching the combustion chamber. 

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The 24-page case against MX-13 manufacturer PACCAR, Inc. contends that the company, which reportedly delivered more than 185,000 Kenworth and Peterbilt trucks in 2022 through its subsidiaries, has been less than truthful with regard to the purportedly high-performance engine. The suit says that although PACCAR has touted that trucks equipped with the MX-13 engine would spend more time on the road and less time in the shop, the fuel injector issue has sparked “a multitude of problems,” including loss of engine power, shaking or vibration of the vehicle, engine knocking or detonation, lean fuel mixtures, RPM fluctuations and total engine failure. 

“The fuel injectors utilized in the MX-13 engine often clog after minimal use and preventative maintenance is of little, if any, help,” the suit states, alleging PACCAR has yet to disclose the problems with the MX-13 engine, found in model year 2021 and newer Kenworth and Peterbilt trucks, to customers or the greater trucking industry.

According to the complaint, one potential cause of the MX-13 fuel system defect concerns the atomization holes in the internal spray tip of the fuel injector. In particular, the case relays that these atomization holes were made too small to allow fuel to pass through the injector properly, and as a result, the holes are prone to partial or complete clogging after only a short period of use. 

Alternatively, the suit shares that the MX-13 fuel system may have been designed or manufactured in a manner that allows contaminants to be introduced into a truck’s fuel supply during regular operation, and that these contaminants could cause the fuel injectors to clog. 

The lawsuit argues that PACCAR knew or should have known that the fuel system in the MX-13 engine was defective at the time the trucks were sold, yet “chose to conceal this information from its customers.” Proposed class members would not have bought the Kenworth or Peterbilt trucks at issue, or would have paid less for them, had they known they were hampered by a potentially dangerous fuel system problem, the case contends. 

“In choosing to conceal this information, PACCAR caused Plaintiff and the Class to unknowingly undertake risks they otherwise would not have undertaken, including risks to their financial wellbeing, and risks to the safety and welfare of their drivers, the occupants of other vehicles and the general public,” the filing reads. 

As of mid-December 2023, PACCAR still has not revealed that the MX-13 engine’s fuel system is defective, the complaint emphasizes, claiming the company continues to equip tractor-trailer and vocational trucks with an engine that could fail at any moment and necessitate costly repairs. Moreover, PACCAR’s temporary fixes for the issue—either cleaning or replacing the fuel injectors—do not address the defect and leave affected trucks “subject to repeated and unpredictable mechanical breakdowns,” the case says. 

“PACCAR’s decision to sell these trucks to unsuspecting customers without revealing the existence and extent of the Fuel System Defect was wrongful and unconscionable,” the suit scathes. “Even more unconscionable was PACCAR’s effort to limit its customers’ remedy to repeated and ineffective repairs, making no provision for the significant downtime and associated losses and expenses customers incur each and every time a repair is necessary.” 

Per the case, PACCAR’s basic engine warranty falls short of its essential purpose and is ultimately unconscionable in that its aim is to “sharply curtail the remedies” available to those who have bought trucks equipped with the MX-13 engine. Overall, the warranty fails because “there was and remains no way to make the MX-13 engine free from defects,” the suit summarizes.

The plaintiff business special-ordered a 2022 Kenworth truck equipped with an MX-13 engine in 2021, the case says. The business claims to have first experienced the MX-13 fuel system problem in March 2022, when the engine had just over 1,000 miles on it. According to the lawsuit, the plaintiff experienced the fuel system defect eight times over the course of its ownership of the truck.

The lawsuit looks to cover all persons and entities in the United States who bought or leased a new vehicle equipped with a PACCAR EPA2021 MX-13 diesel engine and made a claim for repairs pursuant to the company’s basic engine warranty for problems related to the vehicle’s fuel injectors. 

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