If the surface is corroded or if the blades are damaged, replace the impeller

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyAxle Inspection
Remove the front and rear axles (see Front/Rear Wheel
Removal).
Visually inspect the front and rear axle for damages.
If the axle is damaged or bent, replace it.
Place the axle in V blocks that are 100 mm (3.94 in.) [A]
apart, and set a dial gauge [B] on the axle at a point
halfway ...
Rocker Arm Installation
Install the both rocker arms [A] so that their marks [B] face
left side.
Replace the tie-rod nut, rear shock absorber nut and
rocker arm nut with new ones.
Apply grease to the inside of the oil seals.
Tighten:
Torque - Rocker Arm Nut: 34 N·m (3.5 kgf·m, 25 ft·lb)
Tie-Rod ...
Troubleshooting Guide
NOTE
Refer to the Fuel System chapter for most
of DFI trouble shooting guide.
This is not an exhaustive list, giving every
possible cause for each problem listed. It
is meant simply as a rough guide to assist
the troubleshooting for some of the more
common difficulties.
Engine Doe ...