98 v70 NA evap canister shut off valve

[cn90]

1+,

The shut off valve is a one-way street.

[sleddriver]

I think you guys talk about the same stuff.
The shut off valve is a simple device:

- When the engine runs, fuel is being pumped ---> creating vacuum in the gas tank.
- Fresh air enters the shut off valve air filter (#1).
- Then it is fed to the charcoal canister (#2) to replace the volume loss created by fuel being consumed.
- This is a "one-way street".

When the system needs to do the diagnostic test, it sends electrical signal to the valve to shut off the flow at #2. Now air cannot enter the system so it can test for leak.

Even with the car off, the flow is one-way: just disconnect it at the canister and blow backward, it will not flow toward the valve, simply the "check valve" is a "one-way valve".

I agree. However I don't think that the shut off valve or anything else in the EVAP system vents to the atmosphere, ever, unless it's broken. That defeats the purpose of an EVAP system.

The fact that not every 98 v70 is alike is one of the reasons this topic is difficult to troubleshoot.

I am willing to be proven wrong...even with my own hand. I have indeed struggled with the dreaded 455 for a VERY long time. At the time of testing, I did think it odd that vapor could escape through the VENT with the ignition OFF, yet it did. Do note that it does pass through the CharCan first though. I do clearly recall smoke coming out of the VENT attached to the fuel filler pipe, with the ignition OFF and the gas cap in place. My vent doesn't look like yours. Mine's a cylinder, whereas yours is pancake. Odd that...I also just noticed that your car is an NA whereas mine is a T5. It was there all along, just overlooked it I guess.

I guess I'll have do an experiment, as CN90 suggested. If my VENT is indeed a CHECK VALVE, it's no longer doing so. I'll have to investigate this with a few Volvo mechanics I know. I will add however, that I no longer have the dreaded P0455 and haven't for many months.

Taking your argument then, with the ignition OFF, the EVAP system should be totally sealed. No gas vapor allowed to escape. So if you fill up in hot Florida or Texas on your way home, pull into a HOT garage, shut down, then close the door and leave, where's that vapor going to go? I guess if the pressure is high enough, it'll pop the gas cap safety valve and vent there. Therefore, the next morning when you open the garage it'll reak of gas, right? It could also flex a hose, put pressure on a fitting that will loosen over time. So if it's NOT high enough to pop the gas cap valve, but enough to pressurize the system, then if you remove your gas cap the next morning, there should be a WHOOOSH, correct? Unless everything has sufficiently cooled and equalized by then, thus reducing the pressure. I'm not sure how long it takes for the exhaust pipe close to the gas tank to cool off to say 85°F. So the worst case here would be a just filled tank, in hot weather, hot car in a hot garage with all doors shut, right?

I'll leave you to it. Didn't mean to annoy! I gladly admit when I'm proven wrong cause it means I just learned something. I'll do some experimenting on my own and I wish you some good luck there.

[98v70dad]

I think you guys talk about the same stuff.
The shut off valve is a simple device:

- When the engine runs, fuel is being pumped ---> creating vacuum in the gas tank.
- Fresh air enters the shut off valve air filter (#1).
- Then it is fed to the charcoal canister (#2) to replace the volume loss created by fuel being consumed.
- This is a "one-way street".

When the system needs to do the diagnostic test, it sends electrical signal to the valve to shut off the flow at #2. Now air cannot enter the system so it can test for leak.

Even with the car off, the flow is one-way: just disconnect it at the canister and blow backward, it will not flow toward the valve, simply the "check valve" is a "one-way valve".

I agree. However I don't think that the shut off valve or anything else in the EVAP system vents to the atmosphere, ever, unless it's broken. That defeats the purpose of an EVAP system.

The fact that not every 98 v70 is alike is one of the reasons this topic is difficult to troubleshoot.

I am willing to be proven wrong...even with my own hand. I have indeed struggled with the dreaded 455 for a VERY long time. At the time of testing, I did think it odd that vapor could escape through the VENT with the ignition OFF, yet it did. Do note that it does pass through the CharCan first though. I do clearly recall smoke coming out of the VENT attached to the fuel filler pipe, with the ignition OFF and the gas cap in place. My vent doesn't look like yours. Mine's a cylinder, whereas yours is pancake. Odd that...I also just noticed that your car is an NA whereas mine is a T5. It was there all along, just overlooked it I guess.

I guess I'll have do an experiment, as CN90 suggested. If my VENT is indeed a CHECK VALVE, it's no longer doing so. I'll have to investigate this with a few Volvo mechanics I know. I will add however, that I no longer have the dreaded P0455 and haven't for many months.

Taking your argument then, with the ignition OFF, the EVAP system should be totally sealed. No gas vapor allowed to escape. So if you fill up in hot Florida or Texas on your way home, pull into a HOT garage, shut down, then close the door and leave, where's that vapor going to go? I guess if the pressure is high enough, it'll pop the gas cap safety valve and vent there. Therefore, the next morning when you open the garage it'll reak of gas, right? It could also flex a hose, put pressure on a fitting that will loosen over time. So if it's NOT high enough to pop the gas cap valve, but enough to pressurize the system, then if you remove your gas cap the next morning, there should be a WHOOOSH, correct? Unless everything has sufficiently cooled and equalized by then, thus reducing the pressure. I'm not sure how long it takes for the exhaust pipe close to the gas tank to cool off to say 85°F. So the worst case here would be a just filled tank, in hot weather, hot car in a hot garage with all doors shut, right?

I'll leave you to it. Didn't mean to annoy! I gladly admit when I'm proven wrong cause it means I just learned something. I'll do some experimenting on my own and I wish you some good luck there.

Yeah, I don't mean to be argumentative. I just want to fix my car. I did this kind of thing for a living on airplanes for almost 15 years and it's frustrating not really knowing how the system is supposed to operate. You can't efficiently fix what you don't understand and trying to understand how the system in my car is supposed to work is difficult without the maintenance manual. I don't claim to know anything more about the system than anyone else here. Actually I don't know that much at all about volvos. Everything I've learned I learned here. I've learned a couple of good things from some of your posts.over the years..lm going to remove the part tomorrow or Saturday and see what gives.

[98v70dad]

Its a nice day in Atlanta and its supposed to get cold this weekend so I decided to make something happen with my shut off valve. I picked up the part around lunchtime and had it replaced by 3:30. Replacing that part is a PITA.

I learned a few things. First sleddriver is correct that you can blow air through the assembly when it isn't energized. I tried this on the brand new part a verified that sleddriver is right and I am wrong. Its OK to be wrong but its better to be right so Kudos to sleddriver!

I got home from the volvo dealer and started the car and found that my shut off valve was still open when the car started its diagnostic vacuum test of the EVAP system. In fact, it never closed. I could only conclude that the valve has failed and I decided to roll the dice and replace it. We'll see how it goes. I took the car for a test drive and found that it runs much smoother at idle. I don't know what to make of it but at least some good has come from replacing the part.

The valve I took out of the car is a Volvo part. I don't see a date stamp on it but NOBODY I buy parts from has any record of me buying a shut off valve. So maybe I just thought I replaced it 2 years ago and its actually a 18 year old part. This makes a good case for keeping records. I was certain I replaced this part and now am not so sure.

Waiting patiently to see if P0455 comes back.

[kahl]

Just for giggles apply 12 volts DC to the valve and see if it closes.

[98v70dad]

Just for giggles apply 12 volts DC to the valve and see if it closes.

Planning to do that eventually.

[sleddriver]

......

It was certainly due if it's the original part. So your SHUT-OFF valve includes the pancake air filter, eh? And there's no one-way valve in the pancake? Not sure why replacing it would cause your car to run smoother. What will help with that is smoking your intake and looking for leaks. My MPG, performance and boost all went UP when I fixed my vacuum/boost leaks. Didn't realize it had fallen off that far over time! Nice to have the WHOOOSH back!

Your sled may also benefit from a thorough throttle body cleaning, new plugs/wires and a bottle of Redline Si-1 fuel-injection cleaner in the gas tank. When that tank's empty, you may want to do it again. Depends on how long it's been. 3M also makes an excellent 3-part FI cleaning kit you can sometimes get for a great deal on Amazon when on sale. BG_44K is another excellent FI cleaner, but at ~ $25/can, expensive.

Good luck with it!

[cn90]

...I learned a few things. First sleddriver is correct that you can blow air through the assembly when it isn't energized. I tried this on the brand new part a verified that sleddriver is right and I am wrong...

I assume that you blew at the port #2 in the photo below, just checking to be sure (this is b/c if one blows through port #1, it will blow through no matter what):




PS: If this is true (one can blow backward on the shut-off valve), then I find it intriguing, why would any engineers design the shut-off valve this way, i.e., allowing gasoline fume to vent out to open air? Maybe the air filter blocks the air flow outward and the normal fuel tank pressure is rarely above ? 1psi. In other words, fuel evaporation alone does not create too much pressure.
Anyway, I love to learn exactly how the hut-off valve works.

[cn90]

Just saw this video, seems legit, please comment on the video...

[98v70dad]

...I learned a few things. First sleddriver is correct that you can blow air through the assembly when it isn't energized. I tried this on the brand new part a verified that sleddriver is right and I am wrong...

I assume that you blew at the port #2 in the photo below, just checking to be sure (this is b/c if one blows through port #1, it will blow through no matter what):




PS: If this is true (one can blow backward on the shut-off valve), then I find it intriguing, why would any engineers design the shut-off valve this way, i.e., allowing gasoline fume to vent out to open air? Maybe the air filter blocks the air flow outward and the normal fuel tank pressure is rarely above ? 1psi. In other words, fuel evaporation alone does not create too much pressure.
Anyway, I love to learn exactly how the hut-off valve works.

I am an engineer and it doesn't make sense to me either but that's what I discovered with the part straight out of the blue box (at a stop light on the drive home actually...couldn't wait). I tried blowing through both ports with the same result ... wide open.

I decided to replace the part because I'm sick of working on it and I was feeling lucky and willing to risk the $122. I was not totally gambling, because the valve failed the last test I was able to give it. I decided to take the car for a drive to heat it up, park it in the driveway. unhook the purge valve on the EVAP canister side, attach a blow tube extension and wait for the purge valve to start pulsing. (this is an easy test for the purge valve also by the way). You only have to wait a few minutes for the pulsing to start if the car is hot. When the purge valve is pulsing the canister stop valve should be closed and mine wasn't. I could hear air coming out of it when I blew on the tube, although not nearly as much as when the car was off. Also, NOBODY I buy from has a record of selling me this part so maybe I just think I replaced it and never actually did. If that's the case its 18 years old and usually one of the first things people replace. So I had two good reasons to gamble.

I would like to understand how this thing works also. I will keep on it and eventually post what I've learned or what I think I've learned. I'm considering a tear down of the removed valve but I don't own a band saw to cut it in half. First I'm going to put 12 v on it and see if it actuates..no point in cutting up a "good part". I will also post my Poem P0455 - my most loyal friend as my last post in the thread when and if I get this fixed.

I have a test drive I take that almost always causes the code at a certain stop light. When my fuel level drops a few more gallons I'm going to try it.