As everybody, who has had any contact with the piezo injectors, knows, the most typical problem of these injectors – leaking (dripping) in low temperatures. So – during the cold start. Why? The fuel (petrol) loses viscosity in low temperatures – it becomes “thinner”.
To detect which injector is leaking, I base my conclusions on INPA. Fuel mixture data and mechanical efficiency of cylinders – these parameters clearly indicate the culprit.
This time – method for them, who (by some reason) trust the mechanical methods.
What to do:
a. unscrew the injectors, turn them “up” and connect them back to the fuel Rail:
b. reconnect plugs;
c. cool down the engine;
d. put paper tissues under the injectors;
e. ask your assistant to start the engine;
f. observe the fuel injected by the injector.
Here is how the correctly working injector looks (injectors 1/2/3/5/6):
And here, the injector of the 4th cylinder:
As we see – in addition to the correctly injected fuel fog, we can clearly see that after several seconds, the drop of the fuel drops. This injector is leaking!
And here are diagnostics data for the same car:
As we see, the STFT of the 2nd bank is around -20%, which means – (at least) one of the injectors of this bank is leaking.
Here is the mechanical efficiency of cylinders:
Marked with red – cylinder No.4 (in this menu, cylinders are displayed by firing order: 1/5/3/6/2/4).
There is no slightest doubt – exactly the injector of cylinder No.4 is leaking.
This injector test is more “powerful” than previously (here) published. This test allows us to check the quality of the injector closing after its injection cycle. Unfornutaley, the following defects can be present:
a. if the injector has been closed for a longer time (even several tens of seconds), it does not leaks;
b. if the injector has recently been opened, it continues to leak for some time.
The test described in this entry can help in cases where no INPA diagnostics data are available, or the mechanic has no skill in analyzing the data.
