DESCRIPTION
Some fuel injected models use an electrical interrupt switch in the fuel system. On General Motors vehicles, if equipped, it is known as a cut-off switch, and is located in the oil pressure sending unit in conjunction with the fuel pump relay. The inertia switch disables the fuel delivery system when the vehicle is struck violently or when vehicle roll-over takes place. It is mounted in various locations, depending on the vehicle model.
MODELS W/O CUT-OFF INERTIA SWITCH
The ECM will cut power to the fuel pump relay when there is a loss of distributor reference signal.
MODELS W CUT-OFF INERTIA SWITCH
On General Motors models with a cut-off inertia switch, there is a pressure switch located in the oil pressure sending unit. The switch contacts, which are open when the engine is off, closed when oil pressure is above 4 psi (0.3 kg/cm 2 ). If oil pressure drops below the preset value, the contacts will open, cutting power to the fuel pump relay.