The modern electronic fuel injection system is being fitted as standard on new gasoline engine vehicles produced worldwide. Crucial to this system is the fuel injector valve, an electronically controlled mechanical valve manufactured to tolerances as small as 1 micron. This valve operates on opening times of between 2 and 15 milliseconds. The fuel inlet port is protected by a fine 20 micron filter screen and, when the valve is opened by an electronic pulse, a precise amount of pressurized fuel is forced through a small metering hole (or holes). The entire injection system depends upon the reliability, accuracy, and performance of fuel injectors working to extremely fine tolerances.
Peak performance is about correct atomization, which means optimum combustion is reliant on correct fuel atomization. For good performance, minimum pollution, good fuel economy, and engine driveability, correct atomization is a requirement. Only two of the injectors in the photo above are functioning correctly: numbers 1 and 5.
What happens when injectors malfunction?
Problems start to occur when deposits, created by chemical contaminates in gasoline, build up on surfaces of the injector, such as the filter screen, pintle valve, pintle head, and valve seat. Such build-ups can dramatically change the performance of the injector and therefore the car's engine.
Tests have shown that a build up inside the injector of only 5 microns can reduce the flow rate through the injector by up to 25%. Any contamination on or in the injector can affect the fuel flow rate as well as changing the fuel droplet size, reducing the combustible content of fuel, causing excessive exhaust pollution, poor fuel consumption, and impaired engine performance.
Diagnosing Injector Performance
Today's vehicles are fitted with self-diagnostic electronics that quickly and accurately pin point a faulty electronic engine component, even while the car is being driven. The injectors however, are part electrical and part mechanical. It is the mechanical aspect of the injector that is crucial to the engine's efficiency and easily affected by contamination.
The mechanical performance of injectors cannot be accurately analyzed, checked or tested, while they are still in the car. Injectors must be removed from the engine and carefully analyzed for leaks, spray pattern atomizations, and actual fuel delivery volumes in a comprehensive diagnostic simulation program. All too often, injectors are overlooked during the common engine diagnositc tests.
