Slow turn over

check engine earth strap and main supply wire to starter and if possible get starter motor currrent draw tested

I had exactly same problem . I chargedmy battry, check voltage . check alternator. And nothing . untill one day it stop all together so Ihad nochoise to look into starter . I took it apart and realise that brushes fuked up as they detiorate they burnt starter armature . So if you having slow turn over look into brushes . I didnt manage to take all starter out .Some gear linkage was on the way . So I took two smal skrew off starter cup and another two 10 on the side , brushesis underneath . chenge brushes before it burnt your starter armature !I have bought brushes £ 13 and £27 for armature from e-bay .You can go for secondhand starter say for £45 , but where is garanty brushes is ok ? Thanks hope it help you . Do not take on me I mean my English , but I try as best as I can .