The National Highway Traffic Safety Administration (NHTSA) is updating its ongoing investigation into a series of high-pressure fuel pump failures affecting diesel-powered Ram, Jeep and BMW vehicles. Almost 500,000 vehicles could be affected, and so far the working theory is that these fuel pumps, supplied by Bosch, are failing due to US junk diesel fuel.
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Automotive news brings us the latest news about the fuel pump mystery. According to documents released by NHTSA this week, and seen by AutoNewsNHTSA’s Office of Defect Investigation is expanding an investigation into auto parts supplier Robert Bosch, based on an investigation that began in October 2021 involving Ram 2500, 3500, 4500 and 5500 trucks of the 2019 and 2020 model year powered by the Cummins-liter7 turbodiesel. six online
These Ram models were prone to stalling or loss of power, attributed to a malfunctioning high pressure fuel pump. And, along with upgrading the investigation to an “engineering analysis,” another step on the way to a full reminder: NHTSA added a bunch of other vehicles to the list: diesel engine 2014-2022 Ram 1500s, 2021-2022 Jeep Gladiators, 2014-2020 Jeep Grand Cherokees, 2020-2022 Jeep Wranglers, as well as 2014-2018 BMW 3 Series, 5 Series and X3 diesel models. Automotive news reports that up to 490,000 vehicles could be affected if the engineering analysis expands to a full recall.
As AutoNews reports, when NHTSA contacted BMW, the automaker “indicated that the failed pumps in their vehicles were caused by an interaction between internal pump components and US market diesel fuel, resulting in increased slippage and an eventual wear surface that generates particles” .
See, while the US recently switched to ultra-low sulfur diesel in 2011, our modern diesel still lags behind what people can buy in Europe. As explained by Hot Shot’s Secret — a company that sells diesel additives aimed at people who drive diesel vehicles for a living — American ULSD can have up to 15 parts per million of sulfur, compared to Europe 10 ppm maximum.
More importantly, American diesel does not have the same lubricity as the European stuff. How Explain Planet Safe Lubricants (which sells non-toxic industrial greases)., lubricity is tested by performing a standardized test in which a ball bearing is scraped back and forth over a metal surface for 90 minutes while bathed in the fuel or lubricant being tested. At the end of the test, the scientists measure the size of the “wear scar” (that is, the flat point) which is worn on the ball bearing. A larger flat spot means that the diesel fuel being tested does a poor job of lubricating the moving parts, as you would want it to do inside a high-pressure fuel pump.
Here’s the (literal) rub: European diesel specifies a wear scar of 460 microns; US diesel fuel allows a larger wear scar of 520 microns. So the diesel coming out of American gas stations does a poorer job of lubricating the moving parts.
This is the theory behind all these Bosch fuel pump failures. As Hot Shot’s Secret pointed out in 2020, a slightly different Bosch diesel fuel pump showed a failure rate of around 7% in the US, compared to 1% in Europe. Now, NHTSA appears to be preparing for a possible recall of a whole host of Stellantis and BMW vehicles affected by a similar problem, which all boils down to America’s nasty diesel.
via CarScoops
