Front derailleur just stopped - but does manually move

[Aroundm21]

I fitted my front Shimano Altus about 2 years ago and it's been until 2 weeks ago when it just refused to budge !

After much investigation of derailleur, cable, shifter, I oiled the derailleur and replaced the cable to no effect.
I've tried several times to tighten the cable, including barrel adjuster anti-clockwise (and feel it tensing) but still no derailleur movement.

It does seem that it's possible to OVER-tense the cable as when very tight, the shifter no longer clicks at all.

If I manually pull the derailleur then it will come out over the big ring as I want. Takes a bit of effort but there's no kick or click. Everything seems fine - although one of the limiting screws is blocked (fully in), it's labelled "L" which I thought is for the smallest ring at the front (which I never use, for severe up-hills).

Any suggestions are appreciated. Two photos in case they help at all; in case it matters, the cable goes over the top so PULLs the derailleur.

 

[Cycleops]

So you are saying that if you release the cable you can move the derailleur across but with great effort? The click comes from the shifter.
Sounds like it’s just locked up through not being used. Treat it to some WD40 and work it to and fro, should become free in time. Set the Hi Lo at the same time and later fine tune it with the cable attached.

 

[T4tomo]

The picture is a funny angle, but that cable routing looks a little odd - is it a bottom pull FD - shouldn't the cable just come straight up from BB guide to the nut?

 

[si_c]

The derailleur will be a little difficult to move by hand due to the spring tension for the return. Sounds like the shifter to me if the derailleur moves by hand.

 

[Ajax Bay]

I think @T4tomo observation is likely correct. The arm is designed for top pull cable routing and since this cable is routed below the BB shell, it needs to be clamped for 'down pull' by just running the cable up to the clamp bolt.
I'd unscrew both limit screws to avoid them interfering with the 'sort out'.
Consider the physics: if you pull on the cable, does it exert torque on the clockwise or anti-clockwise (from the front)?

 

[Aroundm21]

Thanks all .... to try to explain ...

- If I pull the derailleur out to the biggest ring then the first cable ring {on the right of both photos, where the cable first comes up from the BB} goes DOWN. So that seems correct: a pull down should pull the derailleur out. That's by thumbing the shifter to make the cable more tense.
(I'm also pretty confident this is how the cable was threaded for 2 years while it worked).

Sorry I don't understand the clockwise/anti-clockwise question. If looking at the bike from the front then the deraileur should move up which perhaps is similar to saying clockwise ?

- My only reflection, from manually pulling it out, is that it is quite stiff and hard to move. I'll oil it again. And looking at the cable, it does feel like a lot to ask to be pulled ....

- The limit screws are a bit suspicious but I believe not the critical issue given that I can pull the derailleur it to where I want it to go (the biggest cog as well as middle one).

As I think the shifter seems fine (only does not work when cable is extremely tense), I'm minded to give the WD40 another day or so, move the derailleur for exercise but then replace the derailleur. If that sorts if then I'll be happy; I just wish I could *understand* why it doesn't work when I can see that it should !