The suction control valve is the executive part that controls the fuel quantity in the high-pressure common rail, which is controlled by ECU. When the Suction control valve fails, the fault light will light up.

Suction control valve fault symptoms

Engine stall

Suction control valve fault symptom one

After the suction control valve is damaged due to aging and other reasons, fuel injection cannot occur, and the fuel does not flow through the valve core and directly enters the high-pressure fuel pump, causing the engine to suddenly stop.

Check: Unplug the suction control valve to check whether there is any deformation, blockage, etc. If there is no problem, check the o-ring rubber condition. If the o-ring rubber condition is damaged, you can replace it with a new one, and reinsert it to start.

Suction control valve fault symptom two

When the control line is short-circuited to the ground, the engine will be turned off instantly, and the engine will be limited torsion if the rail pressure is too high.

Suction control valve fault symptom three

The low end of the suction control valve is short-circuited to the ground: the 3.5V control line is grounded. Once this control line is short-circuited to the ground, the ECU will not be able to continue to control the suction control valve. At this time, the current of the suction control valve will reach the maximum value, so the normally open suction control valve oil passages will be completely closed, and the vehicle will show an instantaneous flameout. The failure phenomenon.

Check: Pull out the suction control valve, turn the ignition switch to the ON position, and measure the voltage of the two pins to the ground. Normally, one is 24V and the other is about 3.3V. If there is no voltage, the circuit is broken.

Plug in the suction control valve, pierce the pin from the back end, measure the voltage of the two pins to the ground, under normal circumstances, the voltage is 24V, start the test, where the drive line should be about 0.3V. Check the resistance of the oil suction control valve, the normal value is 2.6-3.2 ohms.

The engine is hard to run

Suction control valve fault symptom one

Suction control valve open circuit failure: the high and low ends of the joint are open, or the line plug is not plugged in well, and the contact is poor, which will cause an open circuit failure. At this time, there is no current in the suction control valve and the spool is at the maximum oil supply position;

Suction control valve fault symptom two

Suction control valve short-circuit fault: the high-end and low-end of the joint are short-circuited. At this time, the suction control valve itself loses current and the spool is also at the maximum oil supply position;

Suction control valve fault symptom three

The high end of the suction control valve is short-circuited to the ground: At this time, the suction control valve itself will also lose current, that is, the suction control valve no longer does work, and the spool is also at the maximum fuel supply position;

The occurrence of the above three conditions will cause the pressure in the common rail pipe to be too high. At this time, it will cause the common rail pressure limiting valve to open and release the pressure. Once the common rail pressure limiting valve fails to open, the engine will be limited in torque, showing a failure phenomenon of driving weakness.

Pressure detection in common rail pipe

Check whether the low-pressure oil circuit is leaking or blocked (tighten the hoops of all pipelines, check whether there are folds, whether the fuel tank is open to the atmosphere, and whether the submarine pipe in the fuel tank is blocked by foreign matter).

Check the fuel return volume of the fuel injector. Under normal circumstances, the fuel return does not exceed the metal plane on the U-shaped card of the fuel injector.

Check the fuel injection volume of the fuel injector. You can take the fuel injector out and connect it out. If the fuel injector is dripping during the startup process, the injector needle valve may be stuck in an open state. Note: For the normal opening and injection conditions of the injector, the rail pressure must be greater than 25M.

Check whether the oil pump pressure relief valve is stuck in an open state, it can be disassembled and cleaned.

Suction control valve fault symptom four

It is very important to avoid the high rail pressure caused by the sticking of the spool. It is important to use qualified fuel oil and diesel filter.

The spool is stuck. For example, when the vehicle is decelerating and going downhill, the engine will enter the deceleration cut-off mode, that is, it will cut off the fuel supply of the injector, and the suction control valve solenoid valve should be completely closed at this time to prevent the oil pressure in the common rail pipe from continuously increasing. However, if the valve core in the suction control valve is stuck at this time, the fuel will continue to enter the common rail pipe, and the oil pressure will continue to rise, causing the pressure limiting valve to be forcibly opened, and the engine enters the protection state. When the speed is limited, it will also show the phenomenon of driving weakness.

The internal valve core of the fuel suction control valve is stuck or worn prematurely. Most of it is caused by excessive impurities in the fuel. Therefore, in addition to refueling at a regular gas station, you must also use a qualified diesel filter to ensure yourself The parts on the vehicle can be used for a longer life.

Severe idling

The continuous opening time is too long and the system pressure is too high, which will cause the engine to enter the fail-safe mode, in which the engine power is limited. At the same time, driving weakness occurs.

If the Suction control valve fails, replace it in time. Inferior Suction control valve has a shorter service life and poor use effect. When it encounters inferior diesel, it may crash immediately. When there is a problem with the suction control valve, how to detect the problem with the suction control valve and whether it needs to be replaced in time.

Fault code

If a fault code occurs, you must use a computer to enter the ECU program to eliminate it after eliminating the fault. You cannot eliminate the fault code at will.

Examples of driving fault codes:

Code P1014: When reversing, the flow in the fuel pressure relief valve exceeds the threshold.

Code P0504: The signals of the brake main switch and auxiliary switch are unreliable.

Code P2299: Throttle and brake signals are unreliable.

Code P0089: Suction control valve stuck.

Code P0628: The suction control valve is open.

Code P0629: Short circuit of suction control valve battery.

Professional tools are needed to detect the fuel suction control valve, such as a fuel suction control valve adjusting device. The drive current that drives the suction control valve can be adjusted, but some people can use a simple method to detect the quality of the fuel suction control valve. The direct method is to use the data flow item of the diagnostic instrument to view the relationship between the drive change of the fuel suction control valve and the rail pressure. With the increase of throttle opening, the follow-up situation of rail pressure changes.

Use a DC stabilized power supply with the same driving voltage of the fuel suction control valve to detect the quality of the fuel suction control valve. Generally, the working current of the dosing unit is below 2000Ma. Gradually adjust from 0 mA to increase the driving current while blowing the suction control with your mouth. Valve valve hole, to see whether the ventilation rate increases with the increase of the current. Of course, this can only roughly judge the working condition of the suction control valve. For resistance measurement, Bosch's resistance is generally 2.3-3.1 ohms, with a maximum current of 1.8A.

Causes of SCV valve failure

open-circuit failure of the metering unit: a disconnection between the high and low ends of the connector, or a line plug that is not plugged in properly and has poor contact, can cause an open-circuit failure when there is no current inside the metering unit and the spool is located in the maximum supply position.

1. Metering unit open-circuit fault: the connector high end and low-end break, or the line plug are not plugged in, poor contact, will cause an open-circuit fault, at this time no current inside the metering unit, the spool is located in the maximum oil supply position.

   
   

2. Short-circuit fault of the metering unit: short circuit at the high end and low end of the connector, at this time the metering unit itself loses current, the spool is also located in the maximum oil supply position.

   
   

3. Metering unit high-end short circuit to the ground: at this time the metering unit itself will also lose current, that is, the metering unit no longer do work, the spool is also located in the maximum oil supply position; the above three failure modes will make the common rail tube pressure is too high, which will lead to the common rail pressure limiting valve will open, pressure relief. Once there is a common rail pressure limiting valve open fault, the engine will enter the limp function, be limited torque, showing the fault phenomenon of driving powerlessness.

   
   

4. Metering unit low-end short circuit to ground: that is, the 3.5V control line overlap. Once the control line is shorted to ground, the ECU will not be able to continue to control the metering unit, at this time the current of the metering unit will reach its maximum value, so the normally open metering unit oil channel will be all closed, the vehicle will exhibit the fault phenomenon of instantaneous stalling.

   
   

5. Spool stuck. Fuel metering unit internal spool stuck or premature wear, most of them are caused by too many impurities within the fuel, diesel filter role failure, too many fuel impurities caused. When the ECU control signal can not be executed, the fuel cut-off, due to spool stuck fuel continues to enter the common rail tube, the oil pressure will continue to rise, resulting in the pressure limiting valve will be forcibly flushed open. At this point, the engine will go into protection and power and speed will be limited to prevent the vehicle from being in danger due to this fault. For repair, this can be disassembled and cleaned, or simply replaced.