I kind of doubt you're going to be able to spin the pump fast enough with a drill to pressurize the system. I'd just put an engine in a see what happens. If nothing is leaking in the back, the system will probably work, but might need new accumulators or the valve may need re-sealing. Those two things are the most common issues in the SLS system. You might also think about replacing the high pressure line from the pump while there is no engine. Less mess and hassle. And then you'll know that it's not going to be an issue down the road.

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