LEFT: The activation piston must be retracted before the new pump can be installed. A spring-loaded tool with mechanical fingers can be used to push it up. The problem is that gravity will let it fall back down unless you use something to keep it retracted.

BELOW LEFT: While you could use a gob of bearing grease to keep the piston retracted, I discovered that ordinary petroleum jelly works just fine. I put a generous dollop of petroleum jelly on my finger, reached in the pump cavity, and pushed the piston all the way up while releasing the mechanical fingers. The gob of jelly prevents the piston from falling, at least for a while. Bear in mind, however, that the piston will slowly come back down, so get the arm of the new pump into the cavity as soon as possible.