! GDI Injector Testing 0:01
GDI injector testing the new GDI injectors are a far cry from normal PFI
0:17
style injectors GDI injection systems use different ways to trigger their
0:24
injectors as well as varying pressures in other words on GDI engines the high
0:31
pressure of the fuel rail changes according to demand by definition this
0:36
means that the electrical conditions will be changing as well on a PFI
0:42
injection system the pressure stays steady at 35 to 60 psi depending on the
0:48
system nominal PFI injectors draw about nine hundred milliamps on the other hand
0:55
GDI injectors use a peek and hold triggering scheme much like the older
1:01
big throttle body injectors with the difference being the voltage and current
1:05
values employed GDI injector internal resistance ranges between 2.62 16.3 owns
1:14
depending on application following will explain exactly how di injectors are
1:21
triggered and how to test them the analysis of the waveform will show you
1:26
how to read the waveform in the oscilloscope or graphing multimeter a
1:31
typical GDI injector current waveform shows a few points of interest
1:36
one is the inject to turn on . signified here by the sudden rise in current this
1:44
turn on . can go as high as 12 amps on the GDI injector again it all depends on
1:51
the fuel demands for that particular engine condition the turn on current
1:56
value will change according to demand
1:59
also remember that the GDI injector open event is way faster than PFI at about
2:06
0.4 25 milliseconds compared to a typical 5 to 15 or higher milli second
2:13
PFI injector open event to is the first stage of the hold current the idea
2:21
behind p can hold is to supply a high-current to quickly activate or open
2:25
the injector needle being that GDI fuel pressures are a lot higher
2:31
you need a lot more current to pray open a GDI injector hence the high 12 amp
2:36
value once the GDI injector is open then in order to protect the injector coil
2:43
current is them clipped down by an internal ECM resistor to about five amps
2:50
this allows to inject it to stay open to the exact same aperture as before or
2:55
during the 12 amp current spike but with a lot less heat 3 is the second stage in
3:02
the hold current which is set about 2.5 amps not all GD I systems have this
3:09
second hold stage but it's so it is there to keep the injector open and
3:14
further protected from heat damage if available
3:18
the second hold stage is employed when injector opening reaches the higher
3:23
values or above 3.5 million seconds following will explain how to test the
3:30
GDI injector testing the GDI injector is no easy matter due to the fact that
3:37
their pressure current and voltage value is always changing by far the fastest
3:44
way to test the electrical health of a GDI injector is using a clamp-on amprobe
3:49
by clamping around either the injector wires you can get a clear reading of the
3:55
current waveform as seen above then compare the readings to the analysis
4:00
that was done before
4:02
there is one other very important aspect of GDI injection which is the fuel
4:08
injection pattern the pattern on a GDI injector is now as important as the
4:14
electrical characteristics
4:16
there are two ways to ascertain the pattern one is using a manual injector
4:22
tester similar to the one used for diesel injectors and a GDI injector
4:27
pulser these small hydraulic jack type little machines can test for pressure
4:33
and injection pattern when the GDI injector is actuated by the pulser it is
4:39
even possible to clean injector residue by using the proper injector cleaning
4:44
detergent fluid with the machine
4:46
it is also important to understand that on any injector well GDI or PFI it is
4:54
important to do a stress procedure before cleaning are electrically testing
4:58
the injector as stress procedure is done by rigging a current limiting resistor
5:03
circuit and actuated the injector for at least one minute a suitable ceramic
5:10
resistor in series with the injector will do
5:13
and in case of GDI injectors a 40 volt power supply that can deliver at least
5:19
five amps is also needed simply activating the GDI injector for about a
5:25
minute at a nominal two to three amps will get the GDI injector stressed out
5:30
and ready for testing
5:31
ninety-nine percent of all injectors fail when nice and hot
5:36
not before after stressing the injector any anomalies will become evident on the
5:42
current waveform which can also be recorded using the injector pulser
