I’ve had a long standing FF89 (purge valve) fault on my "90 Sovereign 4.0L for some time and after much searching and numerous tests, thought the ECM may not have been grounding and therefore not activating the purge valve. Turns out, I was wrong! The electrical switching part of the equation is working. Maybe…
What’s happening is that the purge valve is closed when the ignition is OFF and open when the ignition is ON.
Isn’t this the opposite of what’s supposed to happen? And if it’s supposed to be open when the ignition is off (makes sense; that way the tank can vent to the charcoal cannister when the car is parked), then what is the likely reason? Does the ECM ground the circuit when the ignition is off, thereby opening the valve? Or is the valve normally open when not energized; ie the ECM grounds the circuit only after the ignition is on. If this is the case, then is my purge valve responding opposite to the way it is supposed to?
Something seems amiss here and I’m just trying to figure out if the replacement purge valve I bought some time back is faulty (operates opposite of the way it’s supposed to), or is the ECM switching the opposite way it’s supposed to (I know, that seems really weird to me that it would suddenly change). Or am I just totally misunderstanding the whole thing?
Thanks for any thoughts you all may have on this.