Custom Post Title as search term

If you register the post type with public set to true, the titles will be included automatically. You shouldn’t have to do anything to make this happen. Something as simple as this from the Codex:

function codex_custom_init() {
    $args = array( 'public' => true, 'label' => 'Books' );
    register_post_type( 'book', $args );
}
add_action( 'init', 'codex_custom_init' );

If you aren’t sure you can test it with this:

function test_custom_types_inclusion($where) {
  if (is_search()) {
    wp_die(var_dump($where));
  }
}
add_filter('posts_where','test_custom_types_inclusion');

That will completely break you search but you can see the raw WHERE clause to confirm that your CPT is included. Look for the post_type IN ( part.

That covers this question:

is there any way to include custom post title as search term[?]

But I think you meant that you want to search the names you use to register the types, not the titles. To include all posts listed in a custom post type– and I don’t see the logic of doing that, as you are going to get a potentially huge number of results, making the search more or less useless– something like this…

function custom_types_inclusion_wpse_81742($where) {
  if (is_search()) {
    global $wpdb;
    $where .= " OR {$wpdb->posts}.post_type="your-type-name"";
  }
  return $where;
}
add_filter('posts_where','custom_types_inclusion_wpse_81742');

But to have your search terms respected you will have to get more complicated.

function custom_types_inclusion_wpse_81742_v2($search) {
  global $wpdb;
  $terms = preg_match_all('/%([^%]+)%/',$search,$matches);
  $ts = array();
  if (!empty($matches[1])) {
    $matches = array_unique($matches[1]);
    if (!empty($matches)) {
      foreach ($matches as $m) {
        $ts[] = "{$wpdb->posts}.post_type LIKE '%{$m}%'";
      }
    }
    if (!empty($ts)) {
      $search .= "OR ((".implode(') OR (',$ts).'))';
    }
  }
  return $search;
}
add_filter('posts_search','custom_types_inclusion_wpse_81742');

Untested but I think that should do it.

Again, I don’t see the logic. Results aren’t going to mean much.