Hopefully this is going in the right place. It is more of a write up than a question.

I am currently battling the dreaded P0442 code and have pulled apart just about everything in the system, resealed and replaced as need be. Today I disassembled the canister purge valve to see if the diaphragm was shot.
I should have taken more pictures but I didn't think about writing it up until I was done.

The canister purge valve is located just under the brake distributor and just aft of the battery on the 2001. It has a green service cap on the forward side. I am not sure about other years but I imagine that 2000+ are in the same area.
To remove it, disconnect the electrical connector (after disconnecting the battery), the two large hoses and the vacuum line on the bottom. The two nuts are 10 mm. It is a bit of a tight fit with the brake lines.
I found it easiest to take it out toward the front of the truck.
Once it is out I used two flat blade screwdrivers to separate the two halves of the larger portion. They pop apart pretty easy. Be careful not to jab the diaphragm inside. It is visible from the outside and is fairly soft rubber. Beware there is a decent sized spring in there that will shoot out.
The spring

The diaphragm looks like this.

When I pulled the cover and spring out I noticed that the diaphragm was only attached in its groove about halfway around. I am wondering it wasn't leaking to atmosphere when the EVAP line is under a vacuum as it is while the PCM is running its test.
I removed the diaphragm to inspect it and found what looked like soot and fine rubber similar to a deteriorated hose under it.


I cleaned the diaphragm with soap and water and removed most of the junk inside it. I put a thin layer of RTV in its groove and its top and reseated it.

Now this next part is only if you want to, but I thought I would post it anyway. It is fairly delicate so if you break it, you can't say I didn't warn you.
I wanted to better understand how this thing worked and to see if there was any junk blocking the solenoid valve so I removed the solenoid. The solenoid is located under the vented cap. There is a groove on the side nearest the valve that its teeth will fit into. It will screw off this way. With that off it should look like this.


Mine had a lot of junk inside it. I used contact cleaner to remove it.

To remove the solenoid take a pair of duck bill pliers and pull the electrical connector pins out. They are stuck in there pretty well and are fairly thin, so be careful. Once those are out the metal keeper can be removed with duck bill pliers. It is in there fairly tight as well and will bend. When that is out, grab the center hollow shaft and pull straight out. The solenoid should come out along with a spring and a little steel disk.


The pic shows the correct order in case they get all jumbled.

I cleaned out the chamber with contact cleaner and the o-ring on the bottom of the solenoid. I also cleaned the steel disk. It was dirty where it mates to the solenoid.

The reassembly is the reverse of the disassembly. When you put the connector pins back in, be careful they will bend if not supported well by the pliers. Theyre a little stiff but not too bad. Be sure to seat the solenoid completely, just press in till it stops. If its not seated all the way, the connector pins won't line up.

I was unable to find any description or operation of this valve online to verify it but the operation as my mind sees it is as follows.

The valve is normally closed and the solenoid is normally off. The diaphragm communicates the EVAP line from the canister with the line going to the intake manifold. The EVAP line comes in at the bottom of the chamber through the large opening and the intake line comes in through the central hole. The diaphragm has little tit on it that seals the intake line hole off when it is closed. The large spring keeps this closed normally. The vacuum line at the bottom of the solenoid communicates with the other side of the diaphragm through a small hole at the bottom of the diaphragm chamber. It also communicates with the solenoid chamber at its bottom under the solenoid. When the engine is running and the solenoid is off, the engine vacuum pulls air through the vented cap, through the central shaft in the solenoid, around the steel disk and through the hole in the solenoid chamber. The spring pressure on the diaphragm keeps it closed and the air chooses the path of least resistance. When the solenoid is activated by the PCM it magnetizes and pulls the steel disk up tight to itself sealing off the atmospheric air to the vacuum, so the vacuum overcomes the spring pressure and opens the diaphragm allowing EVAP vapors to leave the EVAP line and enter the intake.







I hope this helps someone to hopefully find and fix a leak without having to throw a part at it and hope for the best. I hope to this sheds some light on how it works as well. This is my first write up so any and all constructive criticism is welcome. Thanks!

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A&P Mechanic EMB-145 CRJ-700
2001 Ford Ranger 4x4 off road 4.0L 4.10 8.8
Blinker, airbox, and throttle cable mods, more to come....

Hey very nice write up and Thank You for posting this info.

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1998 Ranger XLT Super Cab 4.0 ohv v6 - 5r55E automatic Trans - 8.8 with 3.55gears - Toreador Red Clear Coat Metallic -Explorer Sport Trac White Faced Gage Cluster -2006 Mirror Swap-16" Mustang wheels with 215-65-16" Falken Tires