Starting issues ....again

[preacherman]

My starter issues have returned. The up rated starter just grinds like duck. A standard version will only turn the engine over for a few seconds before solenoid dropping out.

I have had this before but can't remember how it was resolved. The car was an automatic and there is a relay taking a live feed into it with a couple of others.

If I short the starter with a spanner it will turn over much better.

Any thoughts on by passing the relay. The engine has just been rebuilt and previously  has been fine for 12 months on the up rated starter but won't have it now. 

The ring gear is ok and  flywheel is not a transit.

[katana]

Find the wire on the Ign. switch that goes 'hot / live' at key posn. 3 (ie starting) Trace it out and disconnect anything attached to it. It needs to be fairly heavy gauge wire as starter soli draws a few amps OR run this wire to a separate relay coil terminal (85 or 86) with other side to ground. Then connect relay 30 to Battery + and remaining relay terminal (87) to starter motor solenoid. The Battery and one to solenoid should be heavy gauge 3.0 or 4.0mm2 would be good.

This should eliminate anything not required to energise the starter motor. Ford used to wire the starter solenoid direct via the Ign switch which is a lot of current through the switch and volt drop through the wiring, introducing the relay takes that off the switch with the relay taking the brunt.