N.J. Stat. Ann. § 2A:82-3

In any claim upon a sealed instrument, a party may plead and set up, in defense thereto, fraud in the consideration of the contract upon which recovery is sought, or want or failure of consideration, as if the instrument were not sealed. In such cases the seal shall be only presumptive evidence of sufficient consideration, which presumption may be rebutted as if the instrument were not sealed.