It's just a solenoid, not pumping or blowing anything.
When energized (regardless of the voltage polarity)
it's let pass the vapours (towards the union),
otherwise blocks the vapour flow.
In the solenoid coils high voltage transient is generated
when their power is interrupted. This could be harmful for
the control circuit, it must be eleminated. For this purpose
a supressor diode is used, which is connected parallel with
the solenoid's coil. The diode could be integrated into the
solenoid or the ECU, can't be seen from outside.
Solenoids with integrated suppressor diodes are sensitive
to supply polarity. Applying wrong polarity to them will
lead to suppressor diode blow. The dead diode won't able
to supress the high voltage transients anymore which kills
the driver stage in the ECU in very short time.
But... according the wiring diagram there's no supressor
diode in the M15 solenoid unit, so the polarity is not important.
Originally pin#1 is pulled towards ground by the ECU,
pin#2 is the positive supply.
Last edited by LoneWolf33; 06-03-12 at 16:55.