Check:
Broken / disconnected vacuum lines at the carbon canister.
Purge control valve on the carbon canister.
Fuel check valve in the vent line near the fuel tank.
Fuel tank vacuum relief valve in the gas cap.
The FSM has the test procedures for all of the above on pages EF&EC-122 thru EF&EC-127.
Courtesy Nissan 280ZX Service Manuals and CDs
Broken / disconnected vacuum lines at the carbon canister.
Purge control valve on the carbon canister.
Fuel check valve in the vent line near the fuel tank.
Fuel tank vacuum relief valve in the gas cap.
The FSM has the test procedures for all of the above on pages EF&EC-122 thru EF&EC-127.
Courtesy Nissan 280ZX Service Manuals and CDs