Extremely high pressure due to accidentally shutting off the pump discharge line, and where no pressure relief equipment existed, could also cause a bulged cover. Place a straight edge across the cover face and check for bowing. The clearance caused by a bulged cover permits by-pass and slippage. If the clearance is appreciable, the pump has little ability to lift and generate pressures. Emergency repair can be made by grinding or sanding the cover flat.
Ideal repair is to replace the cover.
When this type of damage is evident, inspect the drive gear for gear teeth damage and for a sheared pin described above. A pump exposed to a chemical not compatible with bronze and stainless steel will deteriorate rapidly to the points and symptoms described for extreme wear. Little can be salvaged. After handling a pump exposed to chemicals, scrub hands thoroughly to prevent bodily harm. A pump subjected to abrasives will show severe scour marks throughout, especially on shaft bearing surfaces.