Diesel fuel powers a 5.9-L Cummins engine through the use of a fuel injector pump. Many vehicle malfunctions are symptoms of a bad pump, which can cause poor engine performance.
The 5.9-L Cummins engine was used in full-size Dodge trucks starting in 1984. Initially, the injector pumps installed in the Cummins engine were mechanical. These mechanical pumps were later replaced by computer-controlled pumps, which offered more efficient fuel consumption and higher power output.
A problematic injector pump may affect the vehicle's idling, power performance and ignition features. Blockage due to fuel contamination is a common cause of a failed injector pump. The pump cannot move fuel through its assembly if the fuel contains a significant volume of debris.
Many fuel-system part failures mimic the problems encountered with a faulty injector pump. Before replacing an injector pump, check for a clogged fuel filter and verify that air has not infiltrated the fuel lines.