starting problem - nissan micra 1996 n reg?

sometimes car wont start- think its immobiliser ,does this control fuel? Have replaced usual..plugs, ht leads fuel filter, rotor arm & battery...this only leaves Immobilisor/ or fuel injectors (but think this is controlled by immobiliser. Only thing i have not checked is Distributor apparently in this model coil is built inside and not available as spare part