— Bosch CP4 fuel pump failures in Ram trucks caused safety regulators to open an investigation in October 2021, but now the probe has been upgraded by the National Highway Traffic Safety Administration.
The original CP4 fuel pump failure investigation included 2019-2020 Ram 2500, Ram 3500, Ram 4500 and Ram 5500 trucks equipped with 6.7-liter Cummins engines.
NHTSA says Ram owners complained their trucks lost motive power or stalled because the CP4 fuel pumps failed.
Safety regulators wanted to learn if the CP4 fuel pump failures affected vehicles from not only Fiat Chrysler but also BMW.
NHTSA contacted both automakers but "determined that sufficient information to identify a comprehensive recall population could not be produced by FCA and BMW."
BMW reported the CP4 fuel pump failures were caused by the use of U.S. diesel fuel and how it worked with the internal fuel pump components. According to BMW, the problem leads to "increased slip and eventual particle-generating wear surface."
More work is underway to determine if the Chrysler CP4 fuel pumps suffer from the same problems as reported by BMW.
The upgraded CP4 fuel pump investigation will look into the engineering specifications for the components inside the fuel pumps, and safety regulators will do a search for any vehicles equipped with the same allegedly defective CP4 pumps.
Just as with the original CP4 pump investigation, the upgraded investigation is to determine if the Bosch CP4 fuel pumps present an "unreasonable risk to motor vehicle safety."
CarComplaints.com will update our website with results of the investigation into CP4 fuel pump failures.