Possible Cause

- Incorrect slow idle adjustment.

- Faulty fast idle solenoid.

- Plugged fuel return system.

- Glow plugs turn off too soon.

- Incorrect pump timing.

- Limited fuel to injection pump.

- Air in injection lines to nozzles.

- Incorrect or contaminated fuel.

- Faulty injection pump.

- Fuel solenoid closes in RUN position.