C-Pump Low Pressure or Asymmetrical Operation™

Spectra Service Bulletin

Low or no pressure

1. A common cause of low or no pressure is the pressure relief valve not seating properly or it may have a bit of dirt or debris in the valve seat. First, make sure the valve is closed firmly hand tight. It is OK to use a pair of pliers on this but remember you are dealing with plastic. Over tightening can damage the part! If this doesn’t solve the problem unscrew the valve completely and briefly start the feed pump to blow out any debris in the valve seat. Reinstall and tighten, test.
    
2. If the pump shifts normally but stalls under pressure then you may have a broken spool valve. Remove one or both of the end blocks to remove and inspect the spool. If the spool is broken, successful field repairs have been made by drilling and bolting the assembly together.
    
3. No pressure can be caused by a crack in one of the annular valve spools. If it is possible to put your ear on top of the valve block you can often hear a hissing sound indicating a leak here. If you have an offshore kit with annular ring than you may effect a field repair. There is no way to repair the valve spool itself. It will need to be replaced.

Asymmetrical C-Pump operation is caused by a fault within the pump itself. The pressures being much higher on one stroke than the other indicates this. There are several causes that can be determined in the field.

1. The first possible cause and the easiest to troubleshoot is a faulty or rolled seal on the main pump shaft. If your pump has been squeaking then this is the probable cause. On the back of the pump there is a pipe plug labeled test port. Remove this plug to see if water squirts out the hole. If there is substantial quantities of leakage then a failed or rolled seal is the cause. Rolled seals have been removed and reinstalled in the field. Lubrication of the shaft with small quantities of silicone lubricant can prevent the problem from reoccurring in the short term.
    
2. A failed annular ring or a leak on an annular ring O-ring can also cause asymmetrical pump operation. Often the replacement of the O-rings or application of small quantities of silicone grease can seal the O-ring leaks. Failed rings may be removed by tapping out with a dowel. Cracks may be hard to see without stressing the part outward. Inspect the part for a crack radiating around the holes.
    

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