WRX Vapor Canister Purge Valve Replacement Write-up

I recently had a problem that I needed to fix prior to passing NYS Motor Vehicle Inspection.

The problem was that when I went to fill up my fuel tank, the pump would shut off after about 3 seconds.  Even after trying repeatedly.  I tried a different gas station, but had the same problem.  After some research on www.NASIOC.com and some other Subaru-related internet forums, the problem seemed to be with the “vapor canister purge valve.”  I was getting an error code P1443 and my ‘check engine’ light was on.

The temporary workaround was to take my tire lug wrench, reach under the car between the charcoal canister and the side of the body, and hit random parts a few times until I heard the “glug glug glug” sound of fuel moving.  Apparently tapping on the purge valve can cause the valve to open and release the pressure, so that you can fill up your tank again.

So, I took some photos and decided to do a write-up.  I had a few minor problems along the way.


The Write-Up

Step 1.  Have a refreshing beverage.  In my case, a frozen lemonade from Tim Hortons.  It’s summer and pretty warm today.
Tim Hortons Frozen Lemonade

Step 2.  Jack the car up.  I prefer to place my jack under the rear differential (use a block of wood between the jack and the rear diff if you want to be more gentle with it).  Place jack stands in front of the rear wheels, similar to the place behind the front wheels where jacks or jack-stands frequently can go.  You could also use ramps if you prefer, just keep the front wheels ‘chocked’ so that the car doesn’t roll.  Always put safety first.
car jacked up under the rear differential and jack stands underneath in front of rear wheels on WRX

Step 3.  Take some pictures before you take anything apart, so that you have a reference when you go to put it all back together.

Step 4.  Remove the charcoal canister
removing charcoal evaporative emissions filter 2004 Subaru Impreza WRX

There are 3 bolts holding this on, two are on the right side of the picture and one on the left side that is hidden from view above.  The two nuts/bolts on the right are actually sunken into rubber grommets that slide onto the mounting bracket.  If you need to take them off, they actually slide right out.

Step 5.  Let the charcoal canister drop down and hang slightly from the rubber hoses so that you can loosen the hose-clamps.  I believe that they are 6mm heads.  I didn’t have a 6mm wrench or socket, so I used an adjustable wrench instead.  Also unplug the wire harness from the purge valve.
loosen the hose clamps from the rubber lines connecting to the charcoal filter, 2004 Subaru Impreza WRX
The bracket below it is a Perrin rear sway-bar mount.  An OEM Subaru mount may not look the same.  In my case I actually lost one of the nuts for the charcoal canister.  I opted to put one on each end of the canister in my case because if not, one of these rubber lines comes dangerously close to the sway bar mount, and could conceivably wear a hold in the line.  This will probably at least give you an engine light and error code for an evap leak.

Step 6.  Remove the canister to access the purge valve assembly.  The rubber hoses should pull right off, be careful not to tear them, or you could end up with a leak in the evap system.
charcoal evaporative canister filter removed, 2004 Subaru Impreza WRX
Above you can see a typical amount of Buffalo, NY rust.  The bolt that has silver coloring around it in the picture is the one I chose to remove.  This will allow the whole bracket and valve assembly to come off.  It has silver coloring because this is an “after” picture where I slathered an optimal amount of lithium anti-seize grease on the bolt and threads.  There is another smaller bolt holding the purge valve to the bracket, but mine was rusted and frozen at this point.

Step 7.  Remove the 17mm bolt holding the bracket to the underbody.
remove 17mm bolt for evap vapor canister purge valve bracket, 2004 Subaru Impreza WRX
You can see the tow-hook in the picture to the right.  Be careful removing this 17mm bolt.  I believe that on the other side there is a nut that is welded to the frame.  If it is sufficiently rusted and you use a large breaker bar to loosen, you could snap off the bolt or break the nut loose from the other side.  If this happens you are in some trouble.  I’m not sure how you would access the other side of this, it might involve cutting a hole in the bottom of the trunk.  Use some penetrating oil, a hammer and some patience if needed.  It might be a bad idea to use a torch due to proximity of the fuel vent lines.
While the valve is still plugged into the wire harness, you can also connect the green test-mode connectors under the driver’s side dashboard, turn the ignition key to ‘On’ and see if the purge valve is making any clicking sounds.  Just to rule out other possibilities, plug volt-meter probes (carefully so they don’t arc) into the end of the plug coming from the car and make sure that it is measuring 12 volts DC or something close.  You can also connect an external 12 volt power source to the valve directly to see if it clicks or not (I used alligator clips with small hex wrenches to touch the contacts inside the valve’s plug).
If you have 12 volts coming out of the car, and the valve is making no sounds, chances are your valve has died.

Step 8.  Remove assembly, unplug the wire-harness from the valve and get to work removing the purge valve from the bracket.
vapor canister purge valve and bracket, 2004 Subaru Impreza WRX
This step was a little tricky because the bolt that holds the purge valve to the bracket is held in place by the plastic of the cylindrical piece.  When the bolt rusts to the nut, you go to unscrew the nut, and the whole bolt rotates and deforms the plastic on the other side.
rusted nut for vapor canister purge valve, 2004 Subaru Impreza WRX
You can see above where the plastic is supposed to hold the square bolt-head in place, but rust usually has other plans.  I used a dremel cut-off disc and boring-out type of head to cut away the plastic on one side.  Otherwise, it’s impossible to get a wrench in there to hold the bolt head still.  Maybe there is a special tool for this, but I’m not fond of special tools 😛
rusted nut for vapor canister purge valve, 2004 Subaru Impreza WRX
Above you can see the other side of this bolt.
trying to hold bolt still with wrench, vapor canister purge valve, 2004 Subaru Impreza WRX
I tried holding the bolt still like this, but there isn’t enough leverage.  This was before dremel-ing out the plastic.
cut away plastic for vapor canister purge valve, 2004 Subaru Impreza WRX
This is the ‘after’ photo showing what plastic was cut away.
removing nut for vapor canister purge valve, 2004 Subaru Impreza WRX
Now you can barely get a wrench in there to hold the bolt head still, you can see a ratchet on the bottom where I can now apply force to the nut.
old vapor canister purge valve on left, new one on right, 2004 Subaru Impreza WRX
Swap out the old valve for the new valve.
take pictures so you put everything back together correctly, 2004 Subaru WRX Impreza
Go back to your original picture to make sure you put everything back together correctly.

Step 9.  Anti-seize EVERYTHING (nuts, bolt threads and metal-to-metal contact places I mean…not electrical contacts). Reconnect hoses;  bolt the bracket back on the car;  bolt the charcoal canister back on;  make sure everything is tight but not over-tightened.  Also reconnect the wire harness plug to the purge valve.  The plug was very tight to connect on my new valve;  make sure it’s on all the way so that it makes electrical contact.
use anti-seize on everything

If you had to reset your ECU to clear an error code (like the P1443 or others), you will have to drive for a bit until your “monitors” are ready.  You can identify this using many types of OBDII scan tools.  Only after the monitors are ready, will you know if the engine light is off for good.  I have read that the monitors will go into ready status if you drive for approximately 15 minutes at highway speeds.  Supposedly the ECU must pass through multiple ‘cycles’ of varying driving conditions before the system is fully ready.  Until then, your engine lights will probably not come on, but the system will still be in a ‘not ready’ state.  The car will be operational, but not paying attention to some sensors just yet.

Good luck and hopefully this helps some others out there.
Thanks for visiting !


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