The green trace shows the injector control circuit voltage.
The waveform below was captured from a vehicle using the setup above: Optional – backprobe supply wire to monitor voltage drop, couple scope to AC and select 500 millivolt scale, position zero line at 350 millivolts.Backprobe control wire with suitable probe to monitor current flow.Arrow points in the direction of current flow (conventional current flow, positive to negative).
Position clamp around either the supply or control wire.Switch on low amp clamp and zero to calibrate.Set channel 2 to 2 Amp scale, (Low amps 20), position zero line at 0.2 amps.Set channel 1 to 100 volt scale, (DC Volts), position 0 zero line at 5 volts.Below is an outline of the steps to setup the test: Mechanical movement of the pintle valve will be observed in the current and voltage traces on the waveform. The fuel outlet is now open and fuel will be delivered on to the back of the intake valve (s). This duration or period is referred to as the injector pulse width.Ī typical pulse width is 2 to 4 milliseconds at idle and as high as 15 to 18 milliseconds at wide open throttle.Ĭurrent flow through the winding will result in the creation of a large magnetic field, which has the effect of “attracting” the pintle valve into the winding. When the injector is to be actuated, the engine control module connects the negative side of the winding to ground through a transistor.Ĭurrent will flow through the injector winding until the path to ground is interrupted. In the diagram below the fuel injector is supplied with a hard live from a fuse. High pressure injectors fitted to direct injection spark ignition and common rail compression ignition engines use hydraulic imbalance to open the injector, so this test is not suitable for these applications. This test is only applicable to low pressure fuel injectors due to the construction and operation of the injector. The mechanical operation of a fuel injector on a spark ignition engine can be assessed with an oscilloscope using a two channel test.
See how a Snap-on lab scope and diagnostic software can help you check voltage and amperage to guide you to a diagnosis when working on a faulty fuel injector.
0 kommentar(er)
