Here are some reasons why you might want to change the fuel pump on a Cummins engine:

1.    Reduced engine performance: A worn or damaged fuel pump can cause a decrease in engine power and performance, resulting in reduced acceleration, rough idling, and difficulty starting the engine.

2.    Increased fuel consumption: A faulty fuel pump can cause the engine to consume more fuel than necessary, resulting in increased fuel consumption and higher operating costs.

3.    Engine stalling: A malfunctioning fuel pump can cause the engine to stall or shut down, which can be dangerous, especially if it occurs while driving.

4.    Low fuel pressure: A damaged or worn fuel pump can lead to low fuel pressure, which can cause the engine to run poorly or not start at all.

5.    Failed emissions test: A faulty fuel pump can cause the engine to emit more pollutants than allowed, causing it to fail an emissions test.

6.    Maintenance: Regular maintenance and cleaning of the fuel pump can help prevent issues such as deposits or corrosion, which can lead to reduced fuel pump performance or failure.

In summary, the fuel pump is a critical component of the engine’s fuel delivery system, and it needs to be in good working order to ensure optimal engine performance and fuel efficiency. Regular maintenance and timely replacement of the fuel pump can help prevent issues that may require fuel pump replacement.