1.      Hunting (fluctuation) in pump performance.

2.      Jerking during acceleration and difficulty starting the engine.

3.      Increased pump temperature or piston (plunger) damage.

4.      Clogged injectors and weak fuel delivery.

5.      Black smoke due to incomplete combustion.

Signs of a Failing Diesel Fuel Filter

1.      Poor engine pull (reduced power).

2.      Engine vibration.

3.      Increased fuel consumption.

4.      Hard starting in the morning.

5.      “Water in filter” warning light appearing.