Hi, welcome to Pico Technology, my name is Barnaby Donoghue, and today I am going to
take you though the guided test for a common rail diesel piezo injector, specifically the
circuit current. Now, this test comes with a big fat warning
and that is never disconnect a piezo injector with the engine running, the reason being
is there is a signal from the ecu to open injector and another signal to close the injector.
If you disconnect it between those two signals, then the injector could remain open, the diesel
could continue to pour into the cylinder and hey presto you’ve got a stuffed engine,
which we want to avoid, and that of course applies to fitting any breakout leads, if
you have to use then make sure that they are not going to disconnect themselves and they
are secure whilst you are running any testing. Right, that over, we now want to access the
test in picoscope and run it. I’ve got picoscope open here, and I’ve
a scope connected to the laptop using a USB port.
Now we go to the automotive menu at the top, we select Actuators and Injector (Diesel)
and then Piezo (current). Once we have done that we see that picoscope
brings up two things, firstly there is the test guidance, so that is the description
of the test, how to do it, and then underneath that, in picoscope itself, there’s an example
waveform, which shows you what we would expect to see, during or after we have run the test,
but not only that, we have all the presets, all the setting that you need to run the test.
You don’t need to do any configuring, picoscope has already done it for you.
Now that picoscope’s set up we need to connect up our amps clamp to the Oscilloscope.
So we have got a low range amp clamp. This one is up to 60 amps on this particular
example, we connect that to channel A of the scope.
We then on this particular clamp we can select a 20 amp range, generally piezo current does
not go above that. We can zero the clamp to remove any offset
and then we can connect it to our wiring link. Now I have used breakout leads here, because
access here is horrendous on this vehicle and you don’t want to watch me remove components
to get to the clamp. So that is all set up, we’re connected.
Now all we need to do is run the test, so because we might want to observe what’s
happening at the injector during cranking conditions, we start the scope first.
Now we start the vehicle. So I can see that I have got the signal
I was expecting to see on Picoscope. I stop the Scope.
Now I can stop the vehicle. So that looks good.
But we can be more precise if we go back to the guided test itself, we can look at the
waveform notes that describes the fact that in this case, we have got two pilot injections
and a main injection, so that is three events per 7 20 degrees per cylinder with piezo injector.
And that all looks good and we have got positive current that indicates that that’s the opening
events and we have got negative currents and they are the closing events and they are amplitudes
for plus and minus 7 amps. That’s all good.
Now you may have another vehicle, maybe you have not got one like this, you can go to
the waveform library, on that we have got waveforms which have been gathered by users
from around the world, and you can select your make, model and engine code, those types
of details and maybe try and find the waveform that's a more accurate match for your
particular vehicle. Maybe you want to understand a bit more about
how Piezo injectors work, why they need a positive and negative current to operate.
And so if you go to the Further guidance you’ll see that there is a description of the Piezo
technology that will explain that. And then at the end there is also a description
of potential faults and associated symptoms, so we have got electrical faults and then
there’s mechanical faults and then we’ve got misfires, that was a potential symptom
or non-start conditions that type of thing. Plus of course related diagnostic trouble codes.
That’s all in our guided test, so I hope
that will get you going on your Piezo injector testing journey.
Thank you for joining us and we will see you next time.
Goodbye.