It's not a good idea to try these drives without the inject mechanism as they are very sensitive. The floppy disc has to be aligned 100% correctly, otherwise the drive won't work.

Soaking the assembly in WD40 alone is not enough: it's good to loosen it up again and remove all the old grease but then you have to apply new grease to the moving parts.

Does the drive still have it's pressure pad ? If not, you won't get it working.