If your Clark Pump is not functioning properly, this is a good method for identifying more common issues.
You can take apart the whole Clark Pump and rebuild it (email the Spectra factory to obtain a rebuild SOP, details at bottom of page), or, if you want to inspect it one part at a time you can use the below procedure that is used when it should be working but is not. Note that if the Clark Pump has not been rebuilt in 5 years, or has seals that are older than 5 years you may encounter leaks from compromised O-rings.
1) Take off the top valve blocks A and B. Pull out the reversing valve spool and look at the annular rings. If there is scratching on one side, pull it out (see video link below) and flip it around and re-install. You can also try to sand out some score marks on the rings or seals of the reversing valve spool.
2) If the Clark Pump is still mounted leave off the end blocks and pull off each cylinder assembly. Make sure that the rod is not scored, if it is, sand it in a circular motion. Look in the pistons and see if they are scored. If so sand them. If the cylinders themselves are scored that can also be a problem. If the scratch can catch a finger nail we replace them. They can be honed out or sanded in a circular motion with 240 grit abrasive.
3) Look to see if there are any pieces of debris in the check valves that can be pulled out. If you have no other smoking guns then you may want to take out each check valve, clean, and re-assemble.
Many times you will find something obvious, fix it, and be on your way. Other times you may find nothing but put it back together and see that everything works great. Unfortunately many times you may still have your issue and need to perform a full rebuild. We do our best to diagnose Clark Pump parts but there are so many moving internal parts that when there is a problem the official recommendation is to perform a rebuild.
More details on our available kits and factory refurbishment options can be found here:
If you are attempting a full rebuild on your own, our PDF of our factory SOP is a valuable reference: