DESCRIPTION
Coasting fuel cut-off system is used on Federal vehicles only. It is used to prevent excessive emissions which could be created by coasting. This system is an auxiliary fuel system operated by a slow cut solenoid.
System consists of a slow cut solenoid valve integral with carburetor, an engine speed sensor, a transmission switch, an accelerator switch, a clutch switch on manual transmission models, and an inhibitor switch on automatic transmission models.
SPEED SENSOR
The speed sensor detects engine revolutions by sensing ignition pulses from the ignition coil. When engine speed exceeds 2000 RPM, the speed sensor turns off and coasting fuel cut solenoid becomes de-energized.
NEUTRAL SWITCH
Installed on transmission shift quadrant, this switch turns on when gear shifter is moved into any gear position. The switch turns off when shifter is placed in Neutral.
With switch on, the coasting fuel cut-off circuit is energized. With switch off, the coasting fuel cut-off circuit is de-energized.
INHIBITOR SWITCH
Installed on the shift lever, this switch turns on when lever is shifted into "D", "L" or "2" position. When switch is on, the coasting fuel cut-off circuit is energized. With switch off, the coasting fuel cut-off circuit is de-energized.
ACCELERATOR SWITCH
The accelerator switch is connected to the accelerator linkage. It is turned on when the accelerator pedal is not depressed. With the accelerator pedal depressed, the circuit is open, and the switch is turned off.
CLUTCH SWITCH
Clutch switch is installed near clutch pedal. With clutch pedal depressed, switch is turned off. With switch off, the coasting fuel cut-off circuit is de-energized.
MAINTENANCE
Inspect components of coasting fuel cut-off system every 15,000 miles. In addition, carburetor adjustment and ignition timing should be checked at same time.
Connect a jumper wire between Black/Yellow and Light Green/White terminals at speed sensor wiring connector. Start engine and check for voltage between Light Green and Black/Yellow terminals. The speed sensor is normal if the voltage is zero when the engine runs at 2100-2300 RPM.
Connect a self-powered test lamp to switch terminals with switch disconnected. Lamp should light with pedal released and go out with pedal depressed. If not, replace switch.
Connect a self-powered test lamp to switch terminals with switch disconnected. Lamp should light with pedal released, and go out with pedal depressed. If not, replace switch.
NEUTRAL & INHIBITOR SWITCH
Disconnect switch and connect test lamp to switch wiring. With gear selector in any position except Neutral, lamp should light. With gear selector in Neutral, lamp should not light. If switch does not respond as described, replace switch.