Usage:
3406C (4CK24722-UP, 3ZJ51745-UP) Truck Engines
An Improved 108-6634 Fuel Injection Pump Group is used in the above truck engines. Previous 3406B and 3406C Engines had a different bonnet-to-barrel seal design.
In some instances, complete sets of fuel injection pump groups were changed in an attempt to fix low power complaints. In some cases on previous engines, changing all six fuel injection pump groups was successful. However, the new bonnet-to-barrel seal design is not a common cause of low power complaints.
When troubleshooting low power or other performance complaints on the above engines, and an injection pump is believed to be the cause of the problem, change only those fuel injection pump groups that are suspect. Do Not change the complete set.