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Isuzu suction control valve

Author: Site Editor     Publish Time: 2020-12-30      Origin: Site

Isuzu 4HK suction control valve

The development of the common rail system is mainly to respond to the exhaust gas regulations of diesel engines, and to further improve fuel economy to achieve the purpose of noise reduction and high power output. The common rail system uses a storage chamber called a rail to store pressurized fuel. The injector contains an electronically controlled solenoid valve to inject pressurized fuel into the cylinder.


Because the engine ECU controls the injection system including injection pressure, injection rate and injection timing, it is not affected by engine speed or load. This can ensure that a stable injection pressure is always maintained, especially in the low engine speed range, and can greatly reduce the amount of black smoke usually emitted by diesel engines during start-up and acceleration.

Therefore, exhaust emissions are cleaner and reduced, and a higher power output is achieved.

Isuzu 4HK suction control valve


Isuzu 6HK suction control valve


The amount of fuel supplied to the rails is controlled by the suction control valve using signals from the engine ECU. The suction control valve is a normally open type (the intake valve opens when the power is off).

The Isuzu 4HK suction control valve (normally open type) uses a linear solenoid valve. The ECU controls the duty cycle to control the amount of fuel supplied to the high-pressure plunger. Because only the amount of fuel required to reach the target rail pressure is sucked in, the driving load is reduced for the feed pump.

When current flows to the Isuzu suction control valve, a variable electromotive force is generated according to the duty cycle, which causes the armature to move to the left. The armature moves the cylinder to the left, thereby changing the opening of the fuel passage and thereby adjusting the amount of fuel.

When the Isuzu 4HK suction control valve is closed, the return spring will contract, thereby fully opening the fuel passage and supplying fuel to the plunger. (Full feed and full discharge). When the Isuzu 4HK suction control valve is opened, the force of the return spring moves the cylinder to the right, closing the fuel passage (usually open). By opening/closing the SCV, fuel is supplied in an amount corresponding to the actuation duty ratio, and the fuel is discharged through the plunger.

Isuzu 4HK suction control valve internal structure

Isuzu 4HK suction control valve

Isuzu 4HK Pressure Limiter

If abnormally high pressure is generated, the pressure limiter will open to relieve the pressure. When the rail pressure reaches about 200 MPa (2038 kg/cm2), it will trip the pressure limiter (valve opens).

When the pressure drops to about 50 MPa (509.5 kg/cm2), the pressure limiter returns to its normal state (valve closed) to maintain proper pressure.

Isuzu 4HK Pressure Limiter

Isuzu NPR suction control valve

Net Weight: 0.25KG


5.2L 317Cu. In. l4 DIESEL Turbocharged

Isuzu NPR suction control valve

Isuzu NPR Pressure limiter

When the internal pressure is abnormally high, the pressure limiter will open to release fuel from the rail.

Isuzu NPR Pressure limiter 8-97318691-0

Causes of Isuzu common fault codes

  • DTC appears P1093, P1087, P0088, P1088/P1259 is generally the interrupt operation of the suction control valve (SCV)/fuel slide.

  • P0087 appears because the fuel rail/system pressure is too low.

  • P0093 appears because a large leak in the fuel system is detected.

Isuzu common fault inspection

  1. Check the limit oil filter,

  2. Pressure stability test.

  1. Start the vehicle. Allow engine coolant to reach an operating temperature of 70°C (158°F) or higher.

  2. Monitor fuel rail pressure (actual, expected) The actual and expected fuel rail pressure when the engine is idling.

Repair procedures

  • Tilt the cab and secure it in place.

  • Disconnect the battery negative (earth) cable.

  • Find the SCV (FRP Regulator) on the supply pump on the left side of the engine (driver).

  • Clean the location thoroughly to remove all dust, debris and dust.

  • Disconnect the electrical connector of the SCV (FRP regulator).

  • Remove the two mounting bolts and discard the bolts. The repair kit comes with new bolts.

  • Carefully remove the SCV (FRP regulator). Check the SCV (FRP) to ensure that both O-rings are held together with the valve.

  • If the O-ring does not come with the valve, remove it from the fuel supply pump.

  • Check the spare SCV (FRP) for dust or debris, and clean it carefully if necessary.

  • Carefully install the new SCV (FRP) into the supply pump. Push the valve firmly until the valve seat is fully inserted into the supply pump.

  • Install two new mounting bolts for SCV (FRP) and tighten to specifications. Tighten the bolts to 6.9-10.8 Nm (61-95 lb-in).

  • Connect SCV (FRP) electrical connector.

  • Connect the battery negative (earth) cable.

  • Start the vehicle and confirm the operation of the vehicle.

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HENSHINE PRECISION Machinery Co.,Ltd.was established in 2012,and it is high-tech enterprise which is professional diesel engine Valve and industrial hydraulic valve research,development,
Manufacturing and sales.Themain research direction:Diesel common rail suction control valve(SCV),




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