Injection Pump Function, Types, and Operation
Injection Pump Function
What is the function of an injection pump?
Its function is to send oil to the injectors at the right time, at the correct pressure, and perfectly dosed for each engine’s working condition. Regarding types of mechanical pumps, they can be linear or rotary. Many brands exist, but Bosch and Lucas are among the most representative.
Different Types of Injection Pumps
Linear pumps and rotary pumps.
Linear Pump Operation
Operation and Flow Regulation of a Linear Pump Element
The pumping element, which has a spiral ramp and a vertical slot, has a constant stroke from bottom dead center to top dead center, driven by the pump’s camshaft. This element also has a rotary movement from the rack, connected to the accelerator pedal. Injection flow depends on accelerator activation—the pumping element’s pivotal position. In other words, injection flow depends on the working stroke, i.e., the ramp’s position relative to the discharge port.
Timing Advance in Linear Pumps
Why does the timing advance on the pumps? To vary the injection start depending on engine speed. With no power in a linear injection pump, the vertical slot is before the discharge port.
Bosch VE Rotary Pump
Bosch VE Rotary Pump: Start of Feed Device Initials
What are the initials of the start of the feed device according to the load on a Bosch VE rotary pump? LFB
Transfer Pump Role
What role does the transfer pump play? It draws gas oil from the tank into the injection pump, pressurizing it.
Regulating Flow in a Bosch VE Pump
How is flow regulated in a Bosch VE pump? By varying the angular position of the ring roll holder relative to the drive shaft, according to engine revolutions, always in the direction of increasing speed to compensate for injection delays in ignition.
Lucas DPC Rotary Pump
Metering Valve Function and Operation
What is the function of the metering valve and how does it work? Its function is to regulate the amount of oil going into the pistons of a Lucas DPC pump, i.e., regulating the amount of diesel injected.
Pump Mounting Devices
What devices are installed to accommodate the pumps? To improve engine performance, specifically torque, consumption, and pollution output.
Overload Operation in Lucas DPC Pumps
How does the overload mechanism operate on Lucas DPC pumps? This mechanism increases flow at low engine speeds for easier starting. It increases the maximum stroke of the pumping pistons as follows: A compression spring pushes brake pads axially against the roll holder. These pads have a tooth that engages a notch in the bracket. When engaged, the pumping pistons’ travel increases (during startup), thus increasing injection flow. With the engine running, a differential valve in the hydraulic head overrides this mechanism by allowing transfer pressure to act on a piston (surge piston). This piston pushes the pads against the compression spring, disengaging the gears, and the pumping pistons return to their normal stroke.
Rotary Pump Draft and Adjustments
Bosch VE Rotary Pump Draft
Explain the draft of a Bosch VE rotary pump on the engine. Using a slider control that acts on the throttle and governor. Far right increases injection flow; far left decreases it.
Lucas DPC Rotary Pump Draft
Explain the draft of a Lucas DPC rotary pump on the engine. Detach the timing pin, rotate the engine clockwise until the pump and clock scale match, then tighten the screws.
Supercharger Mission
What is the supercharger’s mission? To set the maximum pump flow based on changes in air pressure generated by the turbo.
Bosch VE Rotary Pump Adjustments
What are the major adjustments made to a Bosch VE rotary pump? Governor shaft adjustment, throttle pump adjustment, cold start adjustment, variable speed stroke adjustment, and full-load flow regulation.
Lucas DPC Rotary Pump Adjustments
What are the main settings and adjustments performed in a Lucas DPC rotary pump? Transfer pressure adjustment and overload differential valve adjustment.
Importance of Pump Timing
Why is it necessary to time injection pumps? The injection pump must be synchronized with the cylinders; otherwise, engine performance is reduced, and starting may be impeded.
Additional Information
Linear Pump Operation and Flow Control
The pumping element, with its spiral ramp and vertical slot, has a constant stroke from bottom dead center to top dead center, driven by the pump’s camshaft. It also has a rotary movement from the rack, connected to the accelerator pedal. Injection flow depends on accelerator activation—the pumping element’s pivotal position. In other words, injection flow depends on the working stroke, i.e., the ramp’s position relative to the discharge port.
Important Pump Test Controls
- Pressure feed pump
- Top shot
- Internal pressure control
- Flow checking and calibration
- Maximum adjustment
- Regulatory controls and adjustments
- Timing advance setting
- Fuel cut-off
- Control of adaptive devices: charge pressure (turbocharged engines), top power depending on load, cold start accelerator, idle elevation depending on temperature, etc.
Metering Valve Function and Operation (Lucas DPC)
Its function is to regulate the amount of oil going into the pistons in a Lucas DPC pump, i.e., regulating the amount of diesel injected.
Lucas DPC Pump Overload Mechanism
This mechanism increases flow at low engine speeds for easier starting. It increases the maximum stroke of the pumping pistons as follows: A compression spring pushes brake pads axially against the roll holder. These pads have a tooth that engages a notch in the bracket. When engaged, the pumping pistons’ travel increases (during startup), thus increasing injection flow. With the engine running, a differential valve in the hydraulic head overrides this mechanism by allowing transfer pressure to act on a piston (surge piston). This piston pushes the pads against the compression spring, disengaging the gears, and the pumping pistons return to their normal stroke.
Injection Pump Function
Its function is to send oil to the injectors at the right time, at the correct pressure, and perfectly dosed for each engine’s working condition. Many brands exist, but Bosch and Lucas are among the most representative.
Transfer Pump Role
It draws gas oil from the tank into the injection pump, pressurizing it.
Linear Pump Camshaft Issue
What to do if the camshaft of a linear pump shows pronounced wear on the cam? Change the camshaft.
Linear Pump Fuel Supply
Tick the correct answer: With no fuel in a linear injection pump, the vertical slot is in front of the discharge port.
Pump Regulators
Why are pump regulators necessary? To limit the maximum and minimum torque obtained when engine load decreases or during idling.
Pressure Regulating Valve (Rotary Pump)
What is the pressure regulating valve’s mission in a rotary pump, and how does it work? It checks excess pressure from the transfer pump. If the pressure inside the pump exceeds the spring rate of the pressure regulating valve, the piston lifts, releasing fuel through the valve to the transfer pump suction side. When pressure returns to normal, the plunger reseats, maintaining regulated internal pressure.
Bosch VE Pump Flow Regulation
How is flow regulated in a Bosch VE pump? By a slider control that acts on the throttle and governor. Far right increases injection flow; far left decreases it.