Remove the servo advance plunger. (Figure 4-105, Left). Using a one inch socket and breaker bar, loosen and remove the spring side piston hole plug. (Figure 4-105, Right). Remove the mechanical light load advance spring and servo advance valve from the advance piston. (Figure 4-106, Left). Next, remove the power side advance piston hole plug.… Read More »
Operations which can be performed individually without removing the pump from the engine are as follows: • Cover seal replacements • Guide stud seal replacements • Throttle shaft seal replacements • Governor weight retainer ring checking procedure • Min-Max governor service The procedure that follows include disassembly, various seal replacements, installation of the pellethane governor… Read More »
Background information of failed governor weight retainer ring: diesel fuel that is contaminated with excessive water or the presence of alcohols found in some additives not normally present in recommended diesel fuels may accelerate failure of the Poly-urethane (Pellethane) governor weight retainer ring in the injection pump. Failure of the ring is heat related and… Read More »
Figure 4-81 shows a typical test stand installation. The test stand incorporates a 2 to 15 H.R electric motor, depending on the particular model used, which drives the injection pump. The stand’s motor simulates the automotive engine with the rpm controlled on the machine by the operator and not by the throttle opening. Various tests… Read More »
A damper orifice is located after the delivery valve. This damper is called a trailing port snubber (Figure 4-79). The trailing port snubber is used to prevent secondary injections and cavitation errosion of the high pressure system by weakening reflected pressure waves. This port trails the discharge port radially and resonates the fuel back into… Read More »
A single, spring loaded, delivery valve (Figure 4-78) is located in the center of the DB2 pump rotor. It serves as a one way check valve to seal the pumping chamber from the injection line and also controls residual line pressure by providing volume unloading. At the beginning of pumping, the delivery valve is displaced… Read More »
A rotor seizure can be due to a loss of clearance between the hydraulic head and rotor during the transient (or warm-up) condition. Heat generated by shearing the oil film at the hydraulic head to rotor interface causes heating of the hydraulic head and rotor. Because the mass of the rotor is less than that… Read More »
The final component that we will examine is the heart of the diesel injection pump; the rotor. (Figure 4-77). Due to the extremely close tolerances of the rotor and head assemblies, a thermal relief groove has been incorporated into the rotor design. Thermal shock can cause a head assembly to contract, resulting in the seizure… Read More »
See Figure 4-76. The 6.2L uses a ball-pivot governor arm which has a slot below the bi-metal strip. This prevents interference with the ball pivot conical extrusion. All governor arms of this style now have a tab at the bottom of the conical extrusion, for better retention. The bi-metal strip is covered by a .012″… Read More »
When idle speed drops due to hot fuel, a bi-metal strip on the governor arm deflects. This creates a “ spring load” on the governor arm causing it to rotate slightly, thus repositioning the metering valve to pass more fuel and increase speed slightly. (Figure 4-75).