sb00 I'm not sure if this helps you

SHUTTLE BLOCK Pumps employs a unique pumping principle - a combination of Rotary and Piston Pump. Two double acting pistons in their respective cylinders at right angles to each other, accomplish this, while the rotor turns without the need for any valving. The shuttle block pump is a self-priming Rotary Pump.
There are only three pumping elements - ROTOR, PISTON and SHUTTLE. Rotor is keyed to a single shaft and runs concentric in pump casing. It has a rectangular slot across its face. The channel shaped piston reciprocates within this slot. A rectangular blocks, shuttle, fits liquid tight in piston slot and reciprocates. The reciprocating action of piston in rotor and shuttle in piston is due to and eccentric pin fixed on the pump cover and engaging the shuttle bore as the rotor turns in the pump casing.
Like a true piston pump, this pump can handle highly viscous liquids or thin volatile material with unmatched suction characteristics and yet smoothly without pulsation this pumping principle unlike centrifugal or gear pumps gently handles the product without breaking it down, emulsifying, foaming, chewing or heating: an added advantage at no extra cost.
Application
1) Fertilizer 4) Petroleum Refineries
2) Food Processing  5) Soap & Detergent  
3) Paint & Resin  6) Railway & Ports

sb00, When you say motor run test, I take it you mean, "checking for proper motor rotation" Instead of relying on a piece of paper, why not go out in the field and look at the equipment to see wether the coupling is removable? If your motor test includes checking the amp loads, disconnecting the coupling won't give you the info.

Hope this helps.
saxon