Hi,

I put a 12V source to my canister vent valve ('02 Escape) to see if is working.

I here clicking, but should I be able to see the plunger move?

Also, how can I test the purge valve?

Thanks.

 

Hand pump like a MityVac w/wo power to it.

 

Thanks, Bill.

Can you explain the steps involved to do that with a vacuum?

 

The valve is normally open or closed like switch. If you connect the hand vacuum pump to either port, it'll hold vacuum or not. Put 12V to it and if it doesn't change its state, it's bad.

If you can get some kind of hose that you can blow into it, you may not need a hand pump although it'll be a lot easier. Since it works with vacuum, it would be better to use vacuum instead of pressure.

 

Thanks Bill! I'll try that and report back to you with the results.

 

Bill,

I just saw in my shop manual, something that no one has ever mention,

FVV (FUEL VENT VALVE).

Does anyone know how this valve functions? Do these valve ever go bad.

Do these valve function in a similar way as a vacuum breaker (will it let air into the tank, (because the tank goes under vacuum you burn fuel off)?

And/or doe the FVV,function as an over pressure relief valve, e.g., if you have the car park out in a hot day does it vent the vapor somewhere tp relieve vapor pressure in the fuel tank.

Could a bad FVV cause a po455 code?

Thanks!!

 

If it's part of the EVAP system, yes. Google "Ford DTC P0455".

 

Is there anyway I could hook up the jump wires to test the purge valve backwards and short something out ?

Thanks!

 

Not sure what your asking.

 

If I hook up the positive and negative test wires from the battery (12V source) to the 2 prongs on the purge valve electrical connection wrong (like, only the positive test wire the the right prong) could you ruin the purge valve?

 

Possibly, if the back-EMF diode is part of the valve solenoid assembly, instead of in the ECM.

The 2010 (many years later!) shows that the purge valve has 12 volts on one side (harness wire color Green) and the other side (harness wire color white-Brown) runs off to the ECM. To open the valve, the ECM applies a ground to the White-Brown wire. The colors may be different in yours, but you could check for what the proper operating polarity on yours should be.

If yours uses the same circuit topology, i.e., positive battery on one side, ECM applies ground to other side, you can:
Disconnect connector from purge valve.
Turn ignition to RUN.
Check each of the two harness wires one by one with voltmeter, with the other voltmeter probe on a good ground. Whichever of the two wires has 12 volts on it, that is the wire that goes to the purge valve pin that should be positive when you power it externally. By default, the other purge pin goes to negative.

 

You've unplugged the valve so it's imposssible to damage the PCM and polarity doesn't matter on the valve.

On a '09, a GN wire has the 12V and the WH-BN goes to the PCM. Your best bet is to use a hand vacuum pump, power the valve, see if its working and go from there.

 

Bill,

My 2010-model info has polarity markings on the schematic for the solenoids controlled by the PCM. I thought that was unusual. I don't know why, that's why I wondered if they moved the back-EMF diodes from the PCM out to the individual solenoids. Having them out at the source of the di/dt would reduce the sharp transient that would occur through the harness wiring as when the diodes were in the PCM front end. If one in testing the solenoid valve applied a current-unlimited source backwards to the diode (if it was indeed in the solenoid valve), it would forward bias it, destroying it.
Another possibility with the polarity marking is that they are using a magnetized core to reduce the current required to operate/hold them, reducing power consumption/power handling/heat in the PCM. Or maybe somebody just liked polarity symbols to be complete!

I really don't know which, and a 2002 could be completely different.

 

I thougth that those diodes had to be at the coil itself? I noticed that on a A/C compressor clutch on a old Buick I was working on.

 

Electrically, it doesn't matter. It can be anywhere in the circuit as long as it's in parallel with the coil. It's there to protect the driver electronics from spikes when the coil's electrical field collapses and induces "back -EMF" into the circuit. The diode shorts that spike to ground.