What Causes the Bosch CP4 Pump to Fail?

Owners of certain GM diesel models have been experiencing serious engine damage due to the failure of the imported Bosch CP4 pump, with which many of these vehicles are equipped. In some cases, the repair bill runs into the five-figure range. According to plaintiffs in recent defective fuel pump lawsuits, GM has failed to take responsibility for these failures, which appear to be caused by a compatibility issue with diesel fuel manufactured in the U.S.

What is the Bosch CP4 Pump?

This pump is designed to deliver diesel fuel at high pressure. The idea is to increase fuel efficiency via the use of a metering mechanism. The Bosch corporate website claims “Robust design for selected and standardized country-specific fuel qualities.” However, it appears that the Bosch CP4 has failed to live up to that particular promise.

Why Does it Fail?

The problem with the Bosch CP4 pump, according to a recent fuel pump class action lawsuit, has to do with the sulfur content of diesel fuel made at U.S. refineries. U.S. environmental regulations limit the amount of sulfur allowed in diesel intended for the domestic market. This affects how well the moving parts of the pump are lubricated. These pumps were originally designed in the 1990s for the European market, where the permitted sulfur content of diesel fuel is higher.

How Does This Cause Engine Damage?

Because of its lower sulfur content, U.S. diesel fuel does not provide adequate lubrication for the Bosch C4 components. As a result, the mechanism sheds small bits of metal, which are then released into the fuel system. As these make their way to the fuel injectors and the cylinders, they essentially “gum up the works,” eventually causing catastrophic engine damage.

Why Did GM Use the Bosch C4 Pump in the First Place?

Plaintiffs in a recent class action lawsuit say that GM began using the fuel pump in question with its Duramax diesel engines, starting with the 2010 model year. While it is true that the Bosch C4 pump can result in better fuel economy and far fewer emissions, GM’s main concern appears to have been to reduce its own manufacturing costs, according to dieseltech.com.

Did GM Know About the Problem?

Although GM denies knowledge of the incompatibility issue between the Bosch C4 pump and U.S.-refined diesel fuel, the information has been available for some time. Warnings were issued as far back as 2002, when the Truck and Engine Manufacturers Association, an organization to which GM belongs, issued warnings about the consequences of using low-sulfur domestic diesel with equipment designed for the European market.

It is worth noting that a number of companies that manufacture aftermarket components offer “bypass kits” for owners of vehicles with the defective fuel pump.

What Models are Affected?

GM vehicles equipped with a 6.6 V8 Duramax engine with Bosch C4 fuel pump include Chevrolet and GMC pickups and vans for model years 2011 to 2016 (see below for details). Other diesel-powered vehicles that use the Bosch C4 include the Ford Super Duty series, the Nissan Titan XD and the Dodge Ram 3500.

Join a Free GM Fuel Pump Class Action Lawsuit Investigation

You may be eligible to join this GM fuel pump class action lawsuit investigation if you bought one of these GM vehicles:

• 2011-2016 Chevrolet Silverado 2500HD (6.6L V8 Duramax LML engine)
• 2011-2016 Chevrolet Silverado 3500HD (6.6L V8 Duramax LML)
• 2011-2016 GMC Sierra 2500HD (6.6L V8 Duramax LML)
• 2011-2016 GMC Sierra 3500HD (6.6L V8 Duramax Diesel Trucks LML)
• 2010-2011 Chevrolet Express (6.6L Duramax LGH engine)
• 2010-2011 GMC Savana (6.6L Duramax LGH engine)
• 2010-2011 GMC Sierra Chassis Cabs/Pickup Box Delete (6.6L Duramax LGH engine)
• 2011-2012 Chevrolet Silverado 2500HD and 3500 (6.6L V8 Duramax LGH engine)
• 2011-2012 GMC Sierra 2500HD and 3500 (6.6L V8 Duramax LGH engine)

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