Isuzu 4HK-1 And 6HK-1 Engine Fuel System Ce Applications

Isuzu 4HK-1 and 6HK-1 Engine Overview
The Tier III CX330 Excavators are equipped with an Isuzu 6HK-1 model common rail fuel system Engine. The Isuzu 4HK-1 model will be used in at least one other Excavator model. These engines have 4 valves per cylinder, operated by a single overhead cam to optimize air flow, fuel economy and emissions. The injector is now located at the center of the piston under the valve cover. The fuel system is now totally electronically controlled. These engines use an water cooled Exhaust Gas Recirculation, (EGR) system, which allows a controlled amount of exhaust gas to return back to the intake. This EGR system is used to reduce the emissions level of the engine. These engines also use an air to air aftercooling intake air system. The air to air intake system ports pressurized air flow between the turbocharger and the intake manifold through an air to air heat exchanger in front of the radiator. The 4HK-1 model has a displacement of 317 cubic inches (in3 ) or 5193 cubic centimeters (cc). The 6HK-1 model has a displacement of 475 cubic inches (in3) or 7790- cubic centimeters (cc).

The ECM calculates the basic injection amount based on the signals from throttle position sensor, boost pressure sensor, crank position sensor, cam position sensor, etc. It regulates the opening/closing period of common rail pressure control valve and the electric activation of each injector according to the common rail pressure, engine coolant temperature, etc. at this time, to correct the optimum injection timing and injection amount.

Isuzu 4HK-1 And 6HK-1 Engine Manual
At engine start (after the key switch is turned to the START position to start the engine,and until the return of the key switch to the ON position), the fuel injection quantity is controlled based on information from the start signal, engine speed, and engine coolant temperature. At low temperature, the fuel injection quantity increases. When the engine starts completely, this boosted quantity mode at starting is cancelled and normal running mode is restored.

The Excavator machine controller communicates with the engine controller (ECM) via the CAN Data Bus system to control engine speed, return to idle command, activate the work modes and also to set the engine speed required for the breaker mode.

The electronic control system for the Isuzu 4HK-1 and 6HK-1 Engines use input information from a number of sensors and from the Excavator controller to determine the quantity and timing of the fuel delivery to the engine. The engine control module (ECM), is located on the inside rear of the cab. The ECM has two connectors, one an 81 pin and one 40 pin, for inputs and outputs. The engine control module requires downloading of control software to give it the ability to control all functions.

Inputs to 40 pin engine harness connector:

1. The common rail fuel pressure sensor has 3 wires and is located on the common rail. This sensor detects the fuel pressure in the common rail, converts the pressure into a voltage signal, and sends the signal to the ECM. Higher common rail pressure provides higher fuel pressure sensor voltage while lower pressure provides lower fuel pressure sensor voltage.
2. The 2 wire variable resistor fuel temperature sensor is installed on the fuel supply pump. The fuel temperature sensor measures the temperature of the drain fuel from the pump. When the fuel temperature sensor is cold, the sensor resistance is high. When the fuel temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the signal circuit.
3. The 2 wire engine coolant temperature sensor is located on the thermostat housing at the right front corner of the engine. The coolant sensor's temperature detection component uses a thermistor. A 5 volt reference voltage is applied at all times to the sensor from the ECM. The ECM detects a voltage change due to a resistance value change in the sensor caused by the coolant temperature change.

Outputs from 40 pin engine harness connector:

1. The engine driven high pressure injection pump pressurizes fuel to feed to the common rail. The injection pump has a suction control valve (SCV), and a fuel temperature (FT) sensor. The suction control valve (SCV) is installed onto high pressure pump section and controls supply of fuel (discharge amount) to common rail. The engine control module (ECM) regulates period of electrical activation time of the SCV to regulate the fuel discharge amount.
2. The exhaust gas recirculation (EGR) system recirculates a part of the exhaust gas to the engine intake to reduce the combustion temperature inside the cylinders to reduce NOx (nitrogen oxides) in the exhaust gas. The EGR valve opening is calculated according to the engine coolant temperature (ECT), the engine speed,and the target fuel injection quantity. The EGR motor is the brushless DC motor,and is driven by three phases. The ECM drives the EGR motor through the EGR motor drive circuits U, V, and W. The motor rotates with a combination of the threephase signals. The ECM sets the Error Code when the EGR motor drive duty is high and the difference between the target EGR position and actual EGR position is large.