The text search engine allows searches to be formed from expressions containing the keywords AND, OR, and NOT, and grouped with parentheses. For example: 

bulletmotor mounts
bulletfinds documents containing 'motor' or 'mounts'
bulletreferences to 'motor mouth' would show up
bulletreferences to 'shock mounts' would show up

bulletmotor or mounts
bulletsame as above

bulletmotor and mounts
bulletfinds documents containing both 'motor' and 'mounts'
bulletfinds all pages containing 'motor mounts' (which is what you want)
bulletreferences to 'starter motor' would not show up
bulletreferences to 'the posse mounts up' would not show up

bulletmotor not mounts
bulletfinds documents containing 'motor' but not 'mounts'
bulletwould find any page with the word 'motor' in it, except those on 'motor mounts'

bullet(fuel not fires) and ECU
bulletfinds documents containing 'ECU', plus anything on fuel that doesn't pertain to fires

bulletsub*
bulletfinds all documents containing words starting with 'sub'
bullet'subframe', 'subliminal', 'subterfuge' ... all references starting with 'sub'