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Fuel pressure detection and failure analysis

Date:2019-03-04Typename:FAQ
fuel pressure

I have recently seen many friends asking me about engine jitter and poor acceleration, and some even don't know how to check fuel pressure. Today, we will tell you about the fuel system, how to measure the oil pressure, and some troubles that will bring you a chat.


First, the detection of fuel pressure

1. Preparation tools (oil pressure gauges, rags, tools, etc.)


2, pressure relief


A, pull the relay


B, pull insurance


C. Drive the car and unplug the fuel pump. The residual oil pressure of the system can be maintained for a few seconds, then automatically turn off the fire. When the vehicle is restarted, the pressure relief operation is completed.


Note The fuel pump relay is generally beigeblue.


3. Connect the oil pressure gauge Generally, there is a diagnostic interface on the oil supply pipeline. For the interface without the interface, we connect it to the oil inlet pipe in the form of a three-way valve connected in the middle.



4. Test content


A, oil supply pressure (idle oil pressure)


B, oil supply


C, adjust the oil pressure


D, the maximum oil pressure


E, residual oil pressure


Oil supply pressure The engine is running at an idle speed. The value displayed on the oil pressure gauge is generally 250kpa.


Oil supply After the engine is running fast, the engine speed is increased to 2600rmin, and the oil pressure should be increased by 21kpa on the basis of the oil supply pressure.


Adjusting the oil pressure When the vacuum hose on the oil pressure regulator is unplugged and inserted, the oil pressure gauge should rise by 20~70kpa. (based on oil supply pressure)


Maximum oil supply pressure When the engine is running at idle speed, clamp the oil return pipe and observe the oil pressure gauge. The displayed value should be increased to 2~3 times based on the oil supply pressure.


Residual oil pressure After the engine is turned off, the value shown on the oil pressure gauge is kept at 140kpa within 20min.




Second, the detection of leakage within the system


1. Preparation tools two pliers, rags, oil pressure gauges, etc.


2. Operation steps


A. Turn the ignition switch on or off repeatedly and start the car, then turn off the flame. When the oil supply line is clamped, the system oil pressure value can be maintained, indicating that the inner leakage is the oil pump assembly. If you can't keep it, proceed to the next step.


B. Turn the ignition switch on or off repeatedly and start the car, then turn off the flame. After the oil pressure is established, the oil return line is clamped, and the system oil pressure value can be maintained, indicating that the inner leakage is the oil pressure regulator. If you can't keep it, proceed to the next step.


C. After the oil pressure is established, the supply and return lines are clamped at the same time, and the oil pressure display is lowered, and it is determined that the fuel injector is leaking.


When talking about the fuel system, the first thing we think of is the fuel pump. Let's talk about the fuel pump and what kind of failure will happen.




Third, the common faults and effects of fuel pumps


1. Safety valve leakage or spring failure


It will cause low oil supply pressure and insufficient oil supply, which will result in unstable or inoperative engine operation, resulting in poor engine engine acceleration or engine weakness.


2, check valve oil leakage


It will cause the vehicle fuel system to not establish residual pressure. When starting the car next time, it is difficult to start, and it takes several times to drive the car.


3, the oil filter is blocked


It will cause insufficient fuel supply to the fuel system. In severe cases, the fuel pump will scream due to wear and tear. It will cause the engine to jerk, the acceleration is poor, and there is no high speed.


4, fuel pump pump core damage


This will cause the fuel system to fail to supply oil. The engine cannot start.


5, fuel pump wear


This will cause the oil pump pump oil pressure to be insufficient, which may cause problems such as difficulty in starting the engine and poor acceleration.


After talking about the fuel pump, let's talk about another big injector of the fuel injection system.




Fourth, the common faults and effects of the injector


1. The injector is blocked


This will cause the injector to not spray or the amount of fuel injected, as well as poor atomization. It will cause the engine power to drop, the acceleration to be slow, the idle speed to be unstable, the easy to extinguish and the engine to work.


2. Injector solenoid or internal circuit disconnection


Will cause the injector to not spray oil. It can cause the engine to work unstable or not work.


3. Fuel injector leakage (internal leakage)


It will cause the pressure of the fuel system to drop, the fuel consumption will rise, and it will cause difficulty in starting the engine, black smoke from the exhaust pipe and shooting.




Fifth. Common faults and effects of fuel filters


1. The fuel filter is dirty and clogged


This will cause the fuel system pressure to drop, resulting in poor acceleration and unstable idling.


2. Install the wrong fuel filter (with pressure valve)


This can cause the fuel system pressure to be too low or too high, resulting in high fuel consumption, black smoke, or poor acceleration.




Sixth, fuel pressure regulator failure


1. Vacuum tube leaks


Unable to adjust the oil pressure, it will cause the engine fuel consumption to increase, the idle speed is unstable, the exhaust pipe emits black smoke, etc.


2. The internal pressure of the fuel pressure regulator is damaged (the oil pressure cannot be adjusted)


Excessive oil pressure can cause engine fuel consumption to increase, idle speed is unstable, and the exhaust pipe emits black smoke.


If the oil pressure is too low, the engine may be insufficiently powered and the starting may be difficult.


3, vacuum diaphragm rupture


The fuel will leak through the vacuum hose to the intake pipe, causing high fuel consumption, black smoke from the exhaust pipe, and difficulty in starting the engine.




Seventh. External leakage of the fuel system


It will cause fuel system pressure drop, high fuel consumption, poor acceleration, and unstable idle speed. There are still certain security risks.

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