No power to starter motor

Tyrell Corp wrote: What if you refit, then power up the starter,with jumpers from B- to motor earthpoint and B+ direct to starter terminal, other battery terminals disconnected -does it crank?

if yes and it cranks ok, but problem persists when battery terminals are re-connected then your fault lies somewhere within the wiring to it.

Re-chcek the starter fitted with the jump leads only: what could be drawing far too high a current when trying to turn the engine might seem to work fine on the bench with no load.

I did all this and got it to crank, using jumper cables, bypassing the starter solenoid. I have no idea what changed..

It sounded weak, but my battery is starting to drop voltage (down to 11.9volts now).

I guess next step is to replace all the wiring and solenoid between the battery and starter?

I guess next step is to replace all the wiring and solenoid between the battery and starter?

No, charge battery fully or use a 12v car battery and check it is still cranking over well. Some of your symptoms could be a duff battery, even if it shows a decent open circuit voltage.

Then do that same test but with just one jumper connected at a time, you may be able to isolate it to just the live or earth side. (ie you are using what you know to be a decent jump lead instead of the main battery feed cables, replacing a part of the circuit at a time and narrowing down the fault further)

If you bridge the solenoid live teminals with a screwdriver it should crank even with the ignition off. Your problem probably lies within the three main battery cables; B- to engine and/or B+ to soleniod, solenoid to starter terminal.