Why won't vacumatic hold more ink?

A colleague of mine, with the loan of a few tools, replaced the
diaphragm on his father's Vac. He had to fashion a replacement
filler tube out of something like a spray can, since there apparently
wasn't one. He loves using the pen, except he came by and told me
today that it doesn't hold much ink. Any suggestions on what might be
the cause? and how to fix it?

Pat

Email address works as is.

Patrick Lamb writes:

A colleague of mine, with the loan of a few tools, replaced the
diaphragm on his father's Vac. He had to fashion a replacement
filler tube out of something like a spray can, since there
apparently wasn't one. He loves using the pen, except he came by
and told me today that it doesn't hold much ink. Any suggestions on
what might be the cause? and how to fix it?

As a guess, either the breather tube is much too short, and gets
submerged below the ink level early in the filling process, or it is a
smidge too long and the plunger/diaphragm hits it.

It's also possible there's an air leak, such as a pinhole in the
diaphagm, or the diaphragm isn't seated correctly in the nipple.

Since these pens were marketed on their superior ink volume, seems
like something is wrong. If it were my pen, I'd start withone of the
above.

Hope this helps! IMHO this is one of the most attractive pens ever
made, even though I don't particularly like writing with them (at
least the standard Vac; the section is just too small in diameter.
I've never tried a Maxima).