Searching the FARs is a bit more complicated.
The FARs search will look in Code of Federal Regulations Title 14: Aeronautics and Space for the term. Many of the sections are extremely long, so finding the term on the page can be difficult. I’ve been using two part process to narrow the search.
First click on the google link and see how long it is. If the page is really long I then use the search feature in my browser to look for the words on the page. Suppose I’m looking for regulations covering tachometers and I’m a Part 91 operator, I’d use the search term “tachometer Part-91”. One of the first few links looks like it has what I’m looking for. It has just § 91.205 on required equipment for VFR, IFR, and Instrument flight. It is fairly short so I can scan it easily. This link contains all of Part 91. It’s way too long to scan. Put the word “tachometer” into the browser’s search function and use it to look for the word on the page. Another way to search the FARs is through the government’s eCFR site.
FAA Books on-line as PDFs
A Google search can find words that are in a PDF but it can’t highlight them in the actual PDF document. On the second line of the search result are the words, “File Format: PDF/Adobe Acrobat – View as HTML”. Click on the “View as HTML” link. The words in your search result will be highlighted. Look for them, or if it is a very long page, use the browser search to find the result you are looking for. If you are sure you have the right document you can download it and use your PDF viewers search function to look for words. The FAA has most of their publications on-line as PDFs. Unfortunately, a lot of them are scanned versions of the book and so are not searchable. The ones below are searchable.