Small Engines (Lawn Mowers, etc.): B&S Intek Plus 18.5 HP OHV -Will Not Start, starter checks, compression release

Question
Good Battery.  Starter checks out good.  Starter turns engine but weakens when compression cycle comes around.  Any suggestions?  I was told this engine may have something called a "compression release spring/key" to aid in starting.  Is this true and/or problem?  Last time used engine ran & worked good.  A week later will not start.  Any help will be appreciated.  Thanks!

Answer
Remove the spark plugs and crank the engine.  Does the engine turn over rapidly?
Disconnect battery.  Clean terminal ends and battery posts. Trickly charge battery overnight and leave spark plugs out.

Reintall plugs, connect battery and see if it starts.
Let me know what happens.
Eric