P0442 Evap Canister Folly Topic is solved

[dyn blin]

With the biblical rainfall this weekend, I worked in my garage on some projects on "my" car and motorcycle I've been putting off while getting the kids' 850 up to stage 0.

On my 97 855 GLT, I've been chasing a "small leak" evap code. As I ran out of daylight, I decided to try to lower the canister without removing the plastic wheel-well skirt . I was "successful" (only to a point) & was careful not to strain the 2 lines and elbows to the PURGE & TANK nipples on the canister (it helped that I changed both elbows 2 years ago and added 6 inches to each of those lines at the same time),

However, I found the larger 9.5mm ID hose from the AIR nipple was cracked (I should have replaced that previously with the others). As I tried to cut the hose past the split, I tugged too hard, and split the other end and pulled it off the Vapor Canister Shutoff Valve (the squat cylinder-shaped valve secured under the driver's side hood hinge). Now I have a PO440 Gross Leak code firing- D'oh!

Besides the double-layered lesson in taking the time to do a job right the first time, I have a 3 questions for the collective before I drill the rivets & pull the skirt next weekend, and install a new hose between the canister and shutoff valve :

• Is the Vapor Canister Shutoff Valve a vent valve? In other words, does it release positive pressure from the canister to the atmosphere?
  Is the valve normally open, and closes with a signal from the harness attached?
  Am I correct in my recollection there are only two wires/leads, and to test I may apply 12 volts to hear it open/close depending on answer to question 2?

Much obliged for the bandwidth.

[jreed]

For the third question, the answer is yes the valve does have two leads. You can definitely test the valve works by applying 12V.

I made a somewhat rambling video showing how I replaced the same hose and tested the valve:

[abscate]

I think it's a normally open valve but I might be getting it confused with the ME7 version which is different.

There are so good write ups in the VRd describing the function of this system

[dyn blin]

Thanks Gents,

I found DeepSouth's thorough write up and operating theory.

viewtopic.php?f=1&t=63069

Mr Reed- Your videos are also a very thorough resource- thank you for the link.

[sleddriver]

• Is the Vapor Canister Shutoff Valve a vent valve? In other words, does it release positive pressure from the canister to the atmosphere?
  Is the valve normally open, and closes with a signal from the harness attached?
  Am I correct in my recollection there are only two wires/leads, and to test I may apply 12 volts to hear it open/close depending on answer to question 2?

Yes. It's normally open. It's only closed when the ECU decides it's time for an EVAP test.
Only two wires. Can also use a 9V battery. It may open/close but the seal may be shot and thus leak during testing. These cars are EXTREMELY FINICKY and the pressures used are so tiny that even 1 psi looks HUGE.

I did an extensive write up on this while assisting 98V70dad.

[dyn blin]

Thanks for the direction SledDriver. I found the thread and your comments here :

98 V70 NA evap canister shut off valve

I find the threshold for error flag surprisingly small for a PO440 code, let alone a PO442!

[sleddriver]

Yep! Pascals are a very tiny unit compared to psi.

Somebody at Volvo really had a bug up their @$$ to go overboard on such a finicky system. No doubt pushed that way by the insane EPA regs. Given that, it was a big surprise to 'dad and others that the SOF remains open 99% of the time to vent the gas tank & char. can.