Unless your partnership predates the Revised Uniform Partnership Act of 1994 ("RUPA"), and except to the extent your partnership agreement provides differently, the following rules apply to your situation. The RUPA is codified as part of the Corporations Code ("CC"), at sections 16100 et seq.
Property acquired or customarily used by the partnership is probably partnership property, even if it stands in the name of an individual partner. CC 16204. Property acquired or used by a partnership belongs to the partnership, not to the individual partners. The individual partners are not co-owners of the partnership property. CC 16203, 16501.
A partner may use or possess partnership property only on behalf of the partnership. CC 16401(g).
Each partner is deemed to have a capital account, credited with capital contributions and a share of profits, and debited for losses, distributions and withdrawals. CC 16401(a).
A partner becomes dissociated from the partnership upon the occurence of one or more of a rather lngthy list of events (CC 16601), including expulsion (CC 16601(3)) or voluntary withdrawal (16601(1)).
When a partner becomes dissociated and the partnership business is not wound up, RUPA sections 16701 through 16705 give the dissociated partner a rather substantial bundle of rights, including the right to be bought out at the value of his share (here, 1/3) as of the date of dissociation. Note in particular CC 16701(a) and (b). The partnership MUST buy out the dissociated partner. The price is the value of the partner's share on the date of dissociation and the partnership as a whole will be valued at the HIGHER of its going-concern value or its net liquidation value on that date.
There are some strict time limits imposed by law for both the dissociated partner to ask for a valuation and buy-out and for the partnership to act by making and funding the offer. The RUPA is pretty straightforward and probably can be understood, at least more or less, by a businessman not trained in law. I suggest you get a copy and skim the entire RUPA, but focus intently on the buy-out part of the law at Corporations Code section 16701. You have substantial but time-limited rights. If you go on line to look at the RUPA, be sure you're looking at the California version!
If or when you need a lawyer to assist, please keep me in mind; I am an ex-entrepreneur and since becoming a lawyer in 1999 have handled quite a few contested partnership break-ups.