Injection Pump Throttle Lever
The mechanical lever on the injection pump that sets the target speed of the governor; the cable of the electronic throttle kit connects to this lever.
The injection pump throttle lever is the mechanical lever found on top of a diesel injection pump that sets the target speed of the governor. Its movement is limited between two mechanical stops: idle at one end and maximum speed at the other. The cable of the electronic throttle kit is connected to this lever and drives the lever only between these two stops; the kit makes no other intervention in the fuel system.
What the lever does and does not do
The lever does not set the fuel flow directly. It gives the governor inside the pump the information "aim for this speed"; the amount of fuel needed to hold that speed is determined by the governor, by looking at the load. This distinction matters in practice: fixing the lever at one angle aims to hold the engine at one speed, but when the load increases a certain drop in speed is the expected behaviour. For this reason the electronic throttle kit is an open-loop system that controls the throttle position; it does not take the place of the engine's own governor.
Why the mechanical condition of the lever is checked first
Before the cable is connected, it must be verified that the lever works properly on its own. With the engine not running, take the lever with your finger from idle to fully open and back. The lever must move without catching and must return to idle with its own spring when released. If the lever works stiffly, if there is play in its joint or if the return spring is weak, no electronic adjustment made afterwards will make up for it. For the behaviour of the joint behind the lever see the definition of the throttle linkage joint.
Points to watch during fitting
The points to watch during fitting are all of them mechanical:
- Connection point: the cable must be connected to the lever as nearly as possible at right angles to the plane of movement of the lever and without play. A pull at an angle creates both loss of force and friction.
- Stroke: the movement of the actuator must finish without the lever coming up against its mechanical stops. If the lever comes up against a stop and the actuator goes on pulling, the cable is put under tension, the stall protection cuts in or the cable stretches over time.
- Return: the lever's own spring brings the lever to idle when the cable is released. If this spring is not working the kit cannot close the throttle.
- Cable route: the cable inside the sheath must not be taken through sharp bends; every bend adds friction and makes the return of the lever harder. How the cable route is to be run is a separate subject.
- Tension at idle: if the cable stays taut at idle the lever cannot close fully and the engine does not come down to idle. Setting the tension is the last step of the fitting.
Why the original lever is not removed
The no-removal top mounting approach of the GS740 and the GS740-3P has to do with exactly this point: the original lever stays in place, it is not taken off; the cable is connected from above. In this way, if the kit is removed the engine returns to its former mechanical use and the throttle lever is left in a state where it can be worked by hand. This approach also keeps the lever's own stops and its return spring in circuit; that is, the mechanical speed limit of the engine has not been left to the electronics.
What to do in practice
Before starting on the kit, note the movement of the lever by hand, the return spring and the position of the stops. After connecting the cable, try it by hand over the full stroke without starting the engine: the lever must not come up against a stop and be strained at any point, and it must return to idle when released. If you are going to use it in a marine environment the corrosion state of the lever and the cable has to be assessed separately; the points to watch in a boat or ship application are different.
The context in which this term is used: Speed control of three pumps on a drilling rig