If you think that more space would help you out then loosen the serp belt and remove the top air pump bolt and 'pivot' it over to give you more room. You don't have to remove it completely.
Ultimately though, and I know it's a b!tch to get back on, you're going to have to manhandle that cap (use both hands) against the force of the spring until you touch the threads then turn slightly to get it started and locked in place. Cleaning the threads on both the cap and the hole help a little also.
Good Luck
