The excerpt and quick view are depending from what is indexed in the documents body. You probably have the Basic HTML Content processor currently enabled in your Coveo.SearchProvider.config (described here : https://developers.coveo.com/display/SC201405/Indexing+Documents+with+Basic+HTML+Content)
You have two options if you want to change this. You may want to have the real HTML of the document and you can use the HTML Content processor described here : https://developers.coveo.com/display/SC201405/Indexing+Documents+with+HTML+Content+Processor.
Starting from the April build, if you want to simply have some fields in your quick view/excerpt, you can add options to this processor. Here are the available options :
IncludeFieldNames - whether you want the field names or not
IncludeTextFieldsOnly - whether to add only text fields in the HTML content
FieldsToInclude - comma separated list of fields to include.
Finally, you could still code your own processor by derivating from IProcessor