Oil pump from an 83 model 1)	Gearshaft pin broke off into this 77 model 2)

• Many used oil pumps have scratches on both the gerotors and pump surfaces that the gerotors ride on.
• But, there is one certain spot that seems to be scratched more times than others. ³⁾
  • It's on the larger of the two pads in the pump body and the cover seem to usually have more wear.
  • Sometimes, the small pad is scratched or damaged also but not always.
  • The gap between the inner and outer gerotors on both the feed and return sides tends to be scratched as in the pics below.
  • Debris caught between these two gears cannot slide over and fall to the other cavity and out of the pump.
  • It gets locked between the gears and ripped across the aluminum surface.

• The inner gerotor spins in this same position as it is mounted to the gearshaft.
• The outer gerotor spins by way of the gears inside the cover but also in the same position to the inner gear as below in operation.
• The gearshaft is off center to the outside gerotors on both feed and return.
• There are 8 teeth on the inner and 9 on the outer gerotor in each set.
• This allows for the cavity between the inner and outer gears for oil transfer.

In theory, no particles of any size should be able to spin around to the small pad due to the pressure generated by the spring washer and the gerotor spacing there. The side toward the motor is where oil is transferred to and from the pump. The inner and outer gears come together on the other side (right side). This spacing relationship doesn't change between the motor side or the outside of the pump due to the offset gearshaft. Left side of 1st pic below goes toward the motor.