How to judge the quality of the suction control valve?

If you have a fuel metering control valve adjustment device. There are two ways to judge good or bad:

 

1. Use the suction control valve adjusting device (signal generator) on the pump to adjust the driving current of the suction control valve to see the change of rail pressure.

 

2. The diesel suction control valve can be removed from the pump, and the driving current of the valve can be adjusted by the suction control valve common rail diesel adjusting device (signal generator) to see the movement of the spool. A 12V DC stabilized power supply can be used to detect the quality of the suction control valve. Generally, the working current of the suction control valve is below 2000 mA. We can gradually adjust the drive current from 0 mA and blow the control valve hole with the mouth to see the ventilation. Whether the amount gradually increases or decreases with the increase of the adjustment current, depends on whether the valve body is normally open or normally closed. So as to determine whether it is issued or blocked, but do not exceed 2000 mA, otherwise, the suction control valve may be damaged.

 

For safety reasons, it is best to use a limited current power supply with the current display. It is better to have a PWM driver. Because different suction control valves have different requirements for frequency.

 

When the suction control valve adjusting device is connected to the fuel pump suction control valve, a "buzzing" sound can be heard, which shows that the coil part is good. The armature and spool valve in most broken suction pressure regulating valve are not flexible or stuck. After some damage, white wear marks can be seen on the valve needle.

The best way is to change parts because the suction control valve is our common spare part, which is used frequently and is relatively inexpensive. If the problem cannot be solved after replacement, it can be reused after removal! Therefore, it is not recommended to waste too much time in judging the quality of the suction control valve during the maintenance process!

 

Common fault codes and fault phenomena in the circuit of the suction control valve:

"Main relay 1 is shorted to ground"

Trouble phenomenon: 

The high end of the fuel suction control valve is short-circuited to the ground.

Vehicle symptoms: 

At this time, the suction control valve itself will lose current, that is, the suction control valve will no longer perform work. The suction control valve will be in its original state, which is normally open or normally closed! Transportation vehicles will have high rail pressure and a speed limit of 1500 rpm. Some vehicles will stall due to low voltage!

 

P0253 "Fuel suction control valve short circuit to the ground"

Trouble phenomenon: 

The low end of the suction control valve is short-circuited to the ground.

Vehicle symptoms: 

The control wire of the suction control valve can also be said to be the ground wire of the suction control valve. Once this line is short-circuited to the ground, the ECU cannot continue to control the suction control valve, and the current of the suction control valve will reach the maximum at this time. Therefore, the oil passages of the normally open suction control valve will be completely closed, and the vehicle will instantly turn off. The oil passage of the normally closed suction control valve will be fully opened, so the vehicle will limit the speed or stall due to the high rail pressure.

Common failures and failure phenomena of the suction control valve in the oil circuit.

 

P0251 "Fuel suction control valve open circuit"

Trouble phenomenon: 

The high and low ends of the suction control valve are open, or the connectors are in poor contact!

Vehicle symptoms: 

If it is a vehicle with a normally open valve, high rail pressure will occur. The vehicle enters a speed limit state! If it is a normally closed valve, it will flame out!

P0252 "Measuring unit short circuit"

Trouble phenomenon: 

The high-end and low-end of the suction control valve are short-circuited!

Vehicle symptoms: 

At this time, the pump suction control valve itself will lose current, that is, the suction control valve will no longer perform work. The suction control valve will be in its original state, which is normally open or normally closed! Transportation vehicles such as Weichai and Xichai will have high rail pressure and a speed limit of 1500 rpm.

P1012 The fuel suction control valve measures incorrectly and the fuel injection quantity exceeds the limit

Failure activation principle:

Because the rail pressure is too low, the fuel suction control valve increases the rail pressure by increasing the valve opening! When the opening of the measuring unit exceeds a certain limit, a fault code will appear! Simply put, the rail pressure is too low

Causes of failure: 

low-pressure oil circuit---oil suction filter clogged, fuel tank breathing hole clogged, coarse filter clogged, low-pressure oil delivery pump worn, fine filter clogged, high-pressure oil pump inlet filter clogged, etc.; high-pressure oil pump plunger wear and insufficient oil, The fuel return volume of the fuel injector is increased.

 

P1014 The fuel suction control valve signal in Overspeed mode is unreliable

Failure activation principle:

When the vehicle is resetting the throttle, the opening is 0%. If the speed at this time is greater than 1000 rpm, the fuel injector will stop fuel injection. This situation usually occurs when the vehicle is coasting or downhill. However, the vehicle still has to maintain a certain rail pressure at this time. If there is a leak in the high-pressure oil circuit, our rail pressure will continue to drop, and the suction control valve will continue to open the valve to increase the rail pressure. A fault code will appear when the limit is exceeded! Therefore, most of the problems after the occurrence of 1014 are high-pressure oil circuit problems!

Vehicle symptoms: the fault light is on, the engine speed is limited, and the torque is limited.

cause of the issue:

1. There is a problem with the sealing performance of the fuel injector, which causes excessive oil return. In some fuel injectors, the valve needle is normally open due to problems such as the fuel nozzle, and the phenomenon of oil dripping or urination occurs. As a result, the suction control valve is too open to cause the fault. From the maintenance experience, there is usually a 90% probability that the 1014 fault code is caused by the injector problem!

  

2. The contact surface of the common rail pressure limiting valve is worn, and the common rail leaks oil causing the rail pressure to be too low. This can be further confirmed by whether the common rail oil return line has an oil return.

  

3. For four-valve injectors, poorly assembled or worn high-pressure pipes will also cause rail pressure to be too low, which will cause 1014 fault code, pipe leakage detection scheme: the first step is to unplug the camshaft position sensor and crankshaft position Sensor; the second step is to pull out the oil return pipe; the third step is to take a taxi; the oil return of the oil return pipe indicates that the pipe has oil leakage. No oil return indicates normally.

 

Failure analysis of common measuring units

In the daily maintenance process, we often encounter the phenomenon that the vehicle speed limit is 1500 rpm. The solution is to replace the suction control valve. But not all vehicles can eliminate the fault after replacing the suction control valve. Why is that? Here we can analyze it in detail!

First of all, we clarify the symptoms, which are also speed-limiting but occur under different activation conditions.

1.The speed limit of the vehicle occurs when the vehicle is accelerating rapidly at high throttle, and most of it occurs in the vehicle starting phase, overtaking, or high-speed driving phase;

2. The vehicle has a speed limit of 1500 revolutions during the uphill process;

3. After a period of time at the high throttle, the speed limit problem occurred when the throttle was retracted. This situation also occurred when the brakes were applied. Many cars were running at high speed and the brakes were clicked and the throttle was applied and the speed limit appeared at 1500 rpm. The phenomenon. Some maintenance personnel thought it was a problem with the brake signal, but in fact, it was not but was caused by retracting the throttle;

4. The speed limit phenomenon appears when the vehicle is going downhill.

 

The four situations of comprehensive appeal can be summarized into two categories!

The first and second types can be summarized as the same phenomenon, that is, the speed limit when the vehicle is in urgent need of fuel. It can be basically determined that the rail pressure is too low. The maintenance direction is whether the injector, injector pipe, high-pressure oil pump, and low-pressure oil circuit are unblocked.

 

The third and fourth phenomena occur when the vehicle does not need oil. At this time, although the vehicle does not use oil, the high-pressure oil pump is forced to work while being dragged by the vehicle. Therefore, the cause of flameout at this time is likely to be excessive rail pressure.

The maintenance direction should consider the following aspects: suction control valve stuck, rail pressure sensor, oil return line blocked, high-pressure oil pump return valve stuck, etc. The fault code that appears at this time is usually P1014---the signal of the fuel suction control valve in the reverse-drag state is not reliable. Most of them are affected by injector problems. This fault code has been introduced in detail above and will not be repeated.

 

Judge whether the oil circuit is good or bad according to the current value of the suction control valve

The ECU monitors the current value and duty cycle of the fuel suction control valve. These two values are displayed in the data stream. Common vehicle fuel suction control valve duty cycle, current value reference!