Try Watching the shutter with no lens and back, hold it towards a bright light.
If you do not se any changes in speeds, have the camera CLA'ed the timing mech is just locked up not a expensive fix.
I managed to Fix my Beater F3 with a AS-Is $29 F3-> I just moved the ASA dial and the missing exposure lock knob, across. I am just waiting for my Bgn $10 Prisim to arrive so I can make a good one (Mine has a cloudy Vew Finder)
KEH Bargin and AS-IS items are (So Far) a great parts supply..........Sometimes you even get a BIG supprise like a mint FE with bad foam for $12
PS- Get a copy of......Nikon Repair Book by Tomas Tomosy:- Fixed alot of cameras with his books