I'm cleaning up my old bike and noticed the gear cables were rusty and beginning to fray so I decided to replace them myself. All went well with the rear and it is working great however I can't seem to get the front working.
I followed the Park Tools guide to adjust the height and angle of the derailleur then connected the cable, making sure to leave some slack in it (as the chain was on the small cog). Then I adjusted the L srcew, again following the Park Tools guide.
However I couldn't change gear as the shifter simply springs back. So I tried loosening the cable but then I could shift as the cable was obviously too loose.
The bike is pretty old, mid 90s and the derailleur just has Shimano SIS on it. I added a couple of pictures but I'm not sure how much help they'll be.
When the FD is on the small chainring there is not supposed to be any slack at all. That is because when you wish to shift to the large chain ring you will lose too much movement at the shifter in just taking up slack. Loosen the binding bolt and with the FD on the small chain ring put a pair of pliers on the cable, take up all the slack you can, hold it tight and then snug down on the binding bolt. Pluck the cable. If it feels taut it should work fine from there ...