Usage:
3406C (8PN) Truck Engines
Description of Change: Engine testing shows the new needle valve body and a needle valve adjustment will correct low idle surging of the engine.
Location of the 4N-5485 Valve Body in the fuel injection pump governor group.
Adaptable To: The new 4N-5485 Valve Body is in effect with 3406C (8PN2906) Truck Engine. The 4N-5485 Valve Body can be used to replace the 7W-4182 Valve Body in the former fuel injection pump governor group on all earlier 3406C (8PN) Truck Engines.
If a new valve body is installed, the 5F-9144 Body Seal and 6H-9691 Needle Valve Seal must also be replaced. Tighten the new valve body to a torque of 6.25 N·m (55 lb in). After the new valve body is installed, turn the needle valve clockwise until it bottoms in the new body, then turn the needle valve counterclockwise 1/2turn. Additional adjustment may be required if other driveability problems (deceleration/acceleration) are encountered.
Cold Weather Starting
With cold engine oil, the 1/2turn needle valve adjustment may slow rack movement to the "fuel on" position. If the engine does not start on the first try, before attempting to start again, fully depress the throttle pedal for 10 seconds minimum. Then release the throttle pedal and start the engine as described in the Operation And Maintenance Manual.