starting motor vs starter motor

starting motor and starter motor both are nouns.

Word	Noun	Adjective	Verb	Adverb
starting motor	Yes	No	No	No
starter motor	Yes	No	No	No

As nouns, starting motor and starter motor are synonyms defined as:

starting motor and starter motor: an electric motor for starting an engine

Other synonyms of starting motor include starter.

starting motor (noun)	starter motor (noun)
an electric motor for starting an engine	an electric motor for starting an engine