In 1996, the EPA Emission Regulations began requiring engines to be equipped with some type of tamper resistant device. Some 3406C Engines have tamper resistant bolts on the fuel ratio control. The tamper resistant bolts will prevent unauthorized changes to the fuel ratio control.
The 3406C Engine has tamper resistant bolts on the fuel ratio control. These bolts should not be removed unless an adjustment is necessary. The adjustment should only be performed by a qualified person. Refer to Disassembly and Assembly, "3406C Diesel Truck Engine".
Adjustment of the Fuel Ratio Control
The fuel ratio control limits the amount of fuel during acceleration. This reduces the amount of exhaust smoke from the engine. Refer to Systems Operation, Testing and Adjusting, "3406C Diesel Truck Engine" for adjustment information.