Clutch Start Switch

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Clutch Disc

Construction Mechanic Basic Volume 2

Clutch Troubleshooting

CLUTCH START SWITCH
Many of the newer vehicles incorporate a clutch start switch into the starting system. The clutch start switch is mounted on the clutch pedal assembly. The clutch start switch prevents the engine from cranking unless the clutch pedal is depressed fully. This serves as a safety device that keeps the engine from possibly starting while in gear. Wires from the ignition switch feeds starter solenoid current through the switch. Unless the switch is closed (clutch pedal depressed), the switch prevents current from reaching the starter solenoid. With the transmission in neutral, the clutch start switch is bypassed so the engine will crank and start.

CLUTCH ADJUSTMENT
Clutch adjustments are made to compensate for wear of the clutch disc lining and linkage between the clutch pedal and the clutch release lever. This involves setting the correct amount of free play in the release mechanism. Too much free play causes the clutch to drag during clutch disengagement. Too little free play causes clutch slippage. It is important for you to know how to adjust the three types of clutch release mechanisms.

Clutch Linkage Adjustment
Mechanical clutch linkage is adjusted at the release rod going to the release fork (fig. 4-9). One end of the release rod is threaded. The effective length of the rod can be increased to raise the clutch pedal (decrease free travel). It can also be shortened to lower the clutch pedal (increase free travel).

To change the clutch adjustment, loosen the release rod nuts. Turn the release rod nuts on the threaded rod until you have reached the desired free pedal travel.

Clutch Cable Adjustment
Like the mechanical linkage, a clutch cable adjustment may be required to maintain the correct pedal height and free travel. Typically the clutch cable will have an adjusting nut. When the nut is turned, the length of the cable housing increases or decreases. To increase clutch pedal free travel, turn the clutch cable housing nut to shorten the housing, and, to decrease clutch pedal free travel, turn the nut to lengthen the housing.

Figure 4-9.- Clutch pedal and linkage.

Hydraulic Clutch Adjustment
The hydraulically operated clutch shown in figure 4-10 is adjusted by changing the length of the slave cylinder pushrod. To adjust a hydraulic clutch, simply turn the nut or nuts on the pushrod as needed.

NOTE

When a clutch adjustment is made, refer to the manufacturer's service manual for the correct method of adjustment and clearance. If no manuals are available, an adjustment that allows 1 1/ 2 inches of clutch pedal free travel will allow adequate clutch operation until the vehicle reaches the shop and manuals are available.