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What's the failure of Direct-Injection High-Pressure Fuel Pumps?

Posted on 6/6/2016 9:39:09 AM

Usually people are afraid to diagnose the failure of direct fuel injection.In fact,comparing to the port fuel injection,the direct injection has the same principle except that it inject more precise amounts of fuel into the combustion chamber so the engine can run leaner and more efficient.

The high-pressure fuel pump decides the success of the direct injection.It is precision-machined to generate fuel pressure to the rail up to 2,500 psi. These high-pressure fuel pumps are typically driven by a camshaft and are able to vary their displacement and output to match the needs of the engine.

There are many reasons to diagnose if you know what to look for.Today China Balin Parts Plant,an reputable diesel injection parts and common rail parts manufacturers,will introduce you 7 main reasons of its failure.

1.Lack of Maintenance
The most common reason for the failure of high-pressure fuel pumps is a lack of oil changes.Wear between the camshaft lobes and the high-pressure pump follower prevents the pump from generating enough piston movement. Less movement of the pump means less pressure.

Because the high-pressure pump is very expensive,i believe no one want any problem from it.So it's better for you to examine the lobes on the camshaft first before installing.A lack-of-power complaint may improve, but it will never be completely corrected.

2. Wrong Oil
After the first step,we have to focus on the quality of the oil.For poor engine oil,it will bring problems of premature wear on the camshaft and high-pressure fuel pump follower.So you need to check with your engine oil suppliers whether it meet the OE specifications.Volkswagen, GM and many other OEMs have oil standards that address wear issues on the camshaft and pump follower.

3. Pressure and Temperature Sensors
While a failed sensor cannot cause a pump to fail, it can cause you to misdiagnose a high-pressure fuel pump. Direct-injection systems use pressure and in some cases temperature sensors to help determine position of the high-pressure pump solenoid.

The information generated by these sensors makes for the best possible combustion event, but these additional sensors can throw you a diagnostic curve ball compared to older port fuel-injected ­systems.

These sensors have a ±2% accuracy rate. If the sensors are malfunctioning, they can influence fuel trims. If a sensor fails or is generating readings outside of set parameters, the system will go into a low-pressure safe mode to prevent damage to the system.

So in order to help you to interpret the data of sensors, it's better for you to get scan tool.


4. Leaks
There is lots of pressure on the direct injector,so possibility of leak may happen.Some leaks may occur when the engine is resting, which will cause severe carbon buildup and a rich fuel reading. Leaks can also cause a longer than normal cranking cycle and possible wear.

Most systems have a specified resting pressure. This is designed to keep a specific amount of pressure in the system when the engine is turned off. Values can be monitored using a scan tool.

Injector balance test and leakdown test are typically included in a enhanced or factory scan tool. These tests can help to spot a leaking injector or pump.

5. Old Calibrations, Reflash Required
As engineers squeeze every bit of energy out of a droplet of fuel, every element in the system is operating on a razor’s edge of driveability problems. Sometimes they get it wrong and they don’t find out until a direct-injection system is in the field and racking up warranty claims.

The pump pressures, camshaft position,pressure solenoid position,together with injector pulses are highly related which can be calibrated to give the best performance and component life.

If you are diagnosing a driveability problem on a direct-injection vehicle or replacing a high-pressure pump, make sure the ECU has the latest calibration. Newer calibrations can help solve wear problems and driveablity issues, and may save you from replacing the pump.

6. Fuel Pump Pressure Solenoid
In order to control the volume and pressure of the high-pressure pump,a solenoid is taking its function by changing the stroke and/or port location. When this solenoid fails, it will be in a low-pressure setting.

7. Ignoring the Signs
Some people like to drive with their check engine light on. They assume it will go out if they put better fuel in the tank, but we all know that this is not true.

A direct-injection engine that has a high-pressure pump issue will go into a limp or low-pressure mode. In this mode, the in-tank pump will take over and the injector open time will increase.

When direct injection is working, the injector is precisely pulsing the injector multiple times to create the best possible fuel/air mixture. In a low-pressure mode, it is less precise. The car will start and run, but the performance will be reduced and the catalyst could be harmed. Engine wear can also occur.

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