wire problem??

Hi all
I have had a problem starting my disco 2.5 td 1997.
Sometimes I can not get it to turn over the.n other times its fine. At first thought it was the battery as it turned over very slow, I tried another one still did it. Put a new starter on as I was told it was that. Cleaned all the earthstraps still no good then the garage said it was the glowplugs so I tested them they are fine. I can sometimes start it by running a wire straight from the battery to the solenoid if I don't drain the battery first, that's why I'm thinking there is a problem with the wire which I have cleaned but not sure so I need some help as I'm getting really fed up now,
Any input would be great.
Thanx mickie

Main wire from battery to starter have you looked for damage/corrosion

Hi I have checked all of the wires the only thing I found was the last owner had cut and joined the one to solenoid,

yes it could be the cable, ive had this problem on a truck before it had been to various garages with mechanics changing batteries and starter then scratching their heads why its not fixed it,

the cable looses conductivity over time and will not allow the current to flow through thats needed for the starter motor, bet you any money the copper strands have turned black and brittle

Think ur right m8 just been out and it didn't start so ran a wire again and it started.
Thanx mickie

Sometimes, those heavy leads can look fine on the outside, but be corroded in the middle.