Ampico troubles:  I usually start to look for problems in the tubing.
Lots of hobbyists and professionals alike can get confused if only one
tube is misplaced; this will throw everything else out of order.

The other place to look is the "amplifier" mounted directly on the
pump.  Sometimes the leather is so deteriorated it gets sucked into
the pump itself and that could cause a major leak; so would the
mis-regulation of the springs on the tail end of the pneumatic
squeezing it shut.

Another common mishap in a rebuild is to accidentally switch the
nipples from the twin tubes that run on top of the crescendo units: one
is free just like any other nipple, but the other has a restricted flow
_inside_ the nipple, a little larger than a bleed cup.

I suspect the purpose of the tiny wire spring inside the valve block
was to increase the positive seating of the valve there.

The best way to test the crescendo units on _any_ model A Ampico is
to set the tempo at zero and cover the tracker bar with blank paper.
You should be able to hear each unit "ticking" much like a wristwatch.
Turning the adjustment screws on the spring mounted on these units will
only change the _time_ between up (loud) and down (soft), and not the
level of loudness.  This adjustment was placed there to determine the
rate of slow/fast crescendo/decrescendo.  The pneumatic itself, the
pouches, valves _must_ be absolutely airtight or else you can regulate
the hell out of these screws for weeks without results.

Once more, listen for that "tss tss tss tss" and use a stethoscope or
plain old tubing on the pallet valve to see whether or not those units
"tick."  It should sound like tss tss tss instead of thhhwha thhwha
etc.

Without the spring (although I never tried it myself) I would suspect
the ticking would be much slower if at all.  Ideally one should hear
two ticks to each second.  (About that rate, anyway, give or take, but
this is an easy thing to determine whether or not you hear the ticking;
if you don't, again, check the correct placement of the nips, spring,
or the leather on the pallet arm.)

Another thought;  could it be as simple as belt slip from motor to
pump?!  Once in a while you get lucky with a simple solution!

On another subject:  sticky action parts -- I have found the chemical
"Perc" to be the perfect (pardon the pun) "solution" to this problem.
I obtain mine from my favorite dry cleaner but I have no idea where
you'd find this elsewhere.  It shrinks the fibers in the felt bushings,
smells awful, burns your eyes but when applied with a hypo-oiler and
using a small heat lamp to dry it off after your action will be freed.

Remember:  a little goes a long way.  If still sluggish, reapply;
I've never had to do this more than twice.

Rusty regards from the rainy northwest;

Eric J. Shoemaker