mk1 jetta starter problem?

hi there, sorry in advance for the long story but want to give an idea of what iv tried and circumstances.

the other day i went to start the jetta (1983 1.3) and the engine turned over…. no suspect noises nothing, but didnt start due to not being started for a while now so didnt suspect anything, left it for a couple of minutes and when i cam eback i turned the key and all the dash lights came on as per the norm but once the key was turned there was nothing! just a very slight whiring noise as if something was moving but was barely hearable. i tired and tried but nothing happened, i tryed wiggling wires and linking my other car up to it incase the battery wasnt up to the task etc, but still nothing. i then proceeded to remove the starter motor to bench test it, when linked up with jumper cables it seems to work as it should. so i cleaned connections and put it back in, still nothing…… any ideas? im stuck.

am i right in saying that there isnt a starter relay or anything stupidly obvious like that?

cheers 

i'm useless in the mechanics dept, but also having a 1.3 jetta with starting problems the other day here's what I found/did.

The isolator flange that sits between the carb and manifold had split. the engine cranked all day long but wouldnt fire for love nor money.

carb off, £15 part swapped and it fired into life 1st time, runs brill again now.

prob not related but that was my problem/solution