Just changed the starter and it still will not start.

i have a working 1.7 puma fiesta so i tryed his ecu on my car with his key and my car starts nd runs first flick of the key,

i have also tryed my crack possition sersor in it and it will not run at all,

im almost posertive that the starter is stealling the ecu's power and when the starter is being cranked the ecu shuts down.