David,
If you unscrew the body from the section with the nib, is there a metal converter with a flat spring that you push down compress the sac in order to fill? This is the squeeze converter.
The touchdown mechanism uses a sac encased in a metal sheath with 3 vent holes - two near the section, and one at the apex of the sheath.
If you unscrew the back of your pen and see a long metal cylinder pull out, then you still have the touchdown mechanism. When you pull it fully out and then drive it in, you should hear a little "whish" as the pen breathes in at the end of the touchdown's run. It's during this "whish" that the ink normally gets sucked into the sac.
If your touchdown has somehow been removed, and you have the squeeze converter, don't despair. They work well, and are in demand. You can get a new Shaeffer piston converter for about $8 on Amazon. I tried one, and it leaked as the gasket seal was poor. Now I understand why people pay over $30 for the old squeeze converter alone.