More 1055/6 Troubles. Front Mech compatibility

My beloved Rourke came to me with a full 105 groupset, apart from the front mech.
I swapped out the horrible mtb derailleur for a cheap pressed steel job I had lying around whilst searching for a 1055 front mech. I found one, cleaned it up and popped it on. It seems my 1055 shifter doesn't pull enough cable for my 1055 mech to shift into the big ring of my 1055 chainset. I tried clamping the cable in several different places to try and increase mech travel for the same amount of cable travel, but to no avail - the pivots got in the way and stopped cable movement completely.
I'm wondering, the top pivot had a stripped bolt, so I swapped it for a bolt from a jockey wheel which was the same length and had the same unthreaded section near the head, but a slightly smaller head. Could this be affecting how much the mech moves?
Any options or do I just need to find another front mech? The whole groupset is beginning to show its age, and rear shifting is losing some of its accuracy, so is the front shifter just past it and not pulling enough cable any more?

Cheers
James

Re:

Sounds like your bb could be too long

Shifters never wear out by losing cable pull. Mechs only ever wear out at the pivot points - some obvious, some not so.

Sounds like theres something wrong with the cable outer. Sometimes its not seated right allowing movement during shifts. This then robs the leverage for the mech to go through its full travel.

legrandefromage":q5p9fbny said:

Shifters never wear out by losing cable pull. Mechs only ever wear out at the pivot points - some obvious, some not so.

Sounds like theres something wrong with the cable outer. Sometimes its not seated right allowing movement during shifts. This then robs the leverage for the mech to go through its full travel.

Click to expand...

But there's no cable outer on a downtube shifted front mech.

I assumed STI

downtube shifter would have no issues whatsoever unless it was mounted incorrectly

The description of the problem sounds to me like a too long BB, the mech reaching its maximum throw

1055 crank = 113mm BB
1056 crank = 107

Should have clarified - its STI, with 113mm bb
The mech isn't at max throw - I can move it manually far enough out that it hits the crank.
With the lower limit adjusted so it almost touches the chain, three clicks of the shifter move the cage roughly as far as one trim click usually would.
Thanks for all the suggestions so far

Re:

As LGF said probably corrosion in the cables strip and clean/replace as necessary

What colour is the mech? Is it the champagne green?

I think it is the champagne finish - that kind of greyish slightly sparkly effect.