Throttle Cable PC120

Compatible with the following equipment:

KOMATSU

• PC120

Part Number: 

What is a throttle cable?

A throttle cable is a push-pull control cable that controls engine speed (RPM) on an excavator. It mechanically links the throttle control, either the operator's lever/dial or an electric throttle motor, to the governor lever on the diesel fuel injection pump.

What it does

When the throttle setting changes, the cable's inner core slides inside its outer conduit and moves the governor lever. That changes how much fuel the injection pump delivers, so the engine speeds up or slows down. Since the hydraulic pump is driven directly by the engine, engine RPM determines how much hydraulic power is available. In practice, the throttle cable controls:

• Working speed and power: high RPM for digging and heavy lifting, lower RPM for fine grading or precise work
• Idle and warm-up: dropping to low idle when the machine isn't working, which saves fuel and reduces wear
• Auto-idle and work modes: on machines with a throttle motor, the controller uses the cable to switch between power, economy and auto-idle settings automatically
• Shutdown: on some older models, a separate stop cable or the end of throttle travel pulls the pump to the fuel-cut position

How it's built

It has a steel inner core that transmits the push and pull, an outer conduit (usually steel-wound with a PVC or nylon sheath) that guides it and resists heat and dirt, threaded bulkhead ends with lock nuts for mounting and adjustment, and eye or ball-joint ends that attach to the motor and governor lever.

Common failure signs

• Engine won't reach full RPM, or won't drop back to idle
• RPM hunts or doesn't match the dial setting
• Throttle feels stiff or sticky (the core is corroded or kinked)
• Engine stuck at one speed (cable snapped or detached)
• Throttle motor fault codes on electronically controlled machines, often because the cable is binding and the motor can't reach its target position

Because the cable sits near the engine, it's exposed to heat, vibration and dust, which is why it's a regular wear part on mid-generation machines such as the Komatsu PC200-6/-7, Hitachi EX/ZX-1 series and CAT 320B/C. Newer common-rail machines control fuel electronically through the ECU and don't use a throttle cable.