See Figure 1
The 1982 and later carbureted engines, use the fuel shut-off system to reduce exhaust emissions during deceleration. The system is operated by an anti-dieseling solenoid valve in the carburetor which is controlled by a vacuum switch or ECU on later ECCS vehicles. When the intake manifold vacuum increases to an extremely high level (which it does during deceleration), the fuel flow of the slow system is shut off by the anti-dieseling solenoid valve. When the intake manifold vacuum drops to a low level, the fuel flow of the slow system is resupplied. The solenoid is energized when the clutch pedal is depressed or the vehicle is placed in neutral.
The fuel shut-off system is further controlled by the clutch switch and gear position switches such as the neutral switch (manual transaxle) and the inhibitor switch (automatic transaxle) to ensure that fuel cannot be shut off even it the manifold vacuum is high enough to trigger the normal fuel shut-off operation.
TESTING & INSPECTION
- ECU controlled systems. Check the clutch and neutral switches for continuity.
- Turn the ignition switch OFF and disconnect the ECU connector, if so equipped. Turn the ignition ON and check for continuity at terminals 4 and 5 to ground. There should be continuity. If not, check the harness.
- Non ECU controlled systems. Disconnect the fuel shut-off relay at the relay center and turn the ignition ON . Check for voltage at the green/red and black terminals. Should be 12 volts with the clutch disengaged and 0 volts with the clutch engaged (free).
- Disconnect the vacuum hose from the vacuum switch. Apply vacuum with a vacuum pump and check continuity through the vacuum switch.
- All systems: Disconnect the solenoid electrical connector and vacuum connector. The engine should stall. If not, replace the solenoid.