My clutch pedal goes all the way to the floor with very little pressure. My old Accord had the same problem and it turned out to be the slave cylinder. Is that the case here as well or could it be due to a lack of fluid?
P.S.
When I pump the clutch, I get enough feedback to be able to shift into gear.

 

My friend has this same problem with his 240sx.

The problem may be the Clutch cylinders. master and slave. Over the years, if you do not have a tight cap on the cylinders, moisture tends to get in the system and corrodes and cause air pockets. This leaves your clutch pedal laying flat out.

To fix this, you need a new master/slave cylinder, and flush the system.

It's not the fluid, it's the air pockets/ moisture in the system.

We put a super silicone cap on the Master, and it's good now. But we still need to flush the system and new cylinders. You must do the same.