Usage:
3406C (3ZJ, 4CK) Truck Engines
Description of Change: A new bonnet is used in the 4P7681 Fuel Injection Pump Group. See the Illustration 1. The new bonnet has to rings on the face that contacts the barrel. See Illustration 2. The inside ring (A) is used for sealing and the outside ring (B) helps support the bushings torque load. The outside ring has one or two notches that go through the ring. These notches prevent high fuel pressure between the rings.
Illustration 1. Location of new 611665 Bonnet (1) and barrel (2) in the 4P7681 Fuel Injection Pump Group.
Illustration 2. Location of sealing ring (A) and load (B) on the new 611665 Bonnet.
Adaptable To: The new 6I1665 Bonnet is a direct replacement for the former Bonnet and will service all 3406B and 3406C Truck. The former bonnet is canceled. The new bonnet in effect with 3406C (3ZJ32541, 4CK9450) Truck Engines.
NOTE: Before installing the pumping elements into the pump housing, be sure the pump bores and timing spacers are clean and free of debris.
The tightening torque for the bushing that holds the 4P7681 Fuel Injection Pump Group in the fuel injection pump housing has not changed. Tighten the bushing to a torque of 245 ±15 N·m (180±11 lb ft.)