98 v70 NA evap canister shut off valve

Post by **98v70dad** » 07 Feb 2016, 20:17

How likely is it for an OEM evap canister shut off valve to fail in two years? It seems unlikely to me but that appears to be the source of my P0455 code. When I blow air into the charcoal canister with the car off I can hear air coming out of it. It seems even stranger that it would fail in the open position but maybe its designed that way.

Post by **jreed** » 08 Feb 2016, 05:17

My memory about the canister shut off valve is that it is open when not energized. This is based on a '97 855 GLT, so it may be different on your '98 V70.

Post by **kahl** » 08 Feb 2016, 06:03

The spare shut off valve that I have is open until power is applied. The part number is 9135805. On my 98 there was not enough hose between the vent valve and charcoal canister to drop the canister down with out the hose being removed from the canister. If you can drop your canister without taking off the hose leading to the vent valve then I would suspect the hose is not attached to the vent valve. The hose should have clamps at the canister and vent valve.

Post by **kahl** » 08 Feb 2016, 06:23

The hoses that were broken on my 98 V70 AWD were the two hoses at the rollover valve, two hoses at the filter leading to the purge valve, the two "U" shaped hoses on the canister and the hose leading from the canister to the vent valve. Make sure your hose routing is correct from the two "U" shaped hoses on the canister top. The hose in the center of the elevated square on the top of the canister goes to the purge valve. After the purge valve check all the hoses leading to the intake.

Post by **98v70dad** » 08 Feb 2016, 15:39

jreed wrote:My memory about the canister shut off valve is that it is open when not energized. This is based on a '97 855 GLT, so it may be different on your '98 V70.

I'm not sure when its supposed to open. It depends on how and when the system cycles. I would expect that with the car parked and off you would want a slight negative pressure in the gas tank and pcv system and you can't have that with the shut off valve open.

At any rate, yesterday I tried it with 1) no key in the ignition (off), 2) key turned to the second position and 3) with the engine running. Same result each time, air heard rushing out of the shut off valve when I blow on it.

I'm going to look closely at it this weekend and see what I find. I'll repeat the blow test with more attention to detail to see what happens.

Post by **98v70dad** » 08 Feb 2016, 18:09

Looks like I don't quite have it right.

This thread describes a couple of components I didn't know about and gives a detailed discussion of evap system operation. It does look like the evap shut off valve is open until the diagnostic leak down test is performed. https://www.matthewsvolvosite.com/forums ... hp?t=54591 This may or may not describe the system in my car but most of it matches up with what I know.

How you can have the shut off valve open when the car is off and not running and not vent gas vapors to the atmosphere is what I don't get. Maybe that's the function of the check valve mentioned. I've done a lot of reading about this and never heard of the check valve mentioned in the link.

If the shut off valve is open and the car is running fresh air would be sucked in by the manifold vacuum so you wouldn't vent to the atmosphere in that case. That makes sense to me. Closing the shut off valve to perform the vacuum test also makes sense.

Post by **cn90** » 08 Feb 2016, 19:05

Below is a generic photo of the EVAP Shutoff Valve.

- The "Vent" word used in different books should be termed "One-way Valve", i.e., air is allowed inside the fuel system and does not allow to exit for obvious reason (pollution control and fuel loss through vaporization). When engine is running, fuel is being consumed, creating vacuum: the "One-way Valve" allows air to enter the system otherwise there will be vacuum to a point where the fuel pump can't pump against so much vacuum.

- The purpose of the Shutoff Valve is for self-diagnosis. If the ECU wants to check the system for leak, the first thing the ECU does is to shut the outside air from coming: this is EVAP Shutoff Valve's function.
a. If the EVAP Shutoff Valve fails "closed": then will be vacuum in the system (open the gas cap and you hear a "whoooosh"...
b. If the EVAP Shutoff Valve fails "open": during testing air is allowed in and the system thinks there is a leak, but in reality there is no hose leak.

: EVAP.jpg (105.09 KiB) Viewed 4791 times

Post by **98v70dad** » 08 Feb 2016, 19:54

cn90 wrote:Below is a generic photo of the EVAP Shutoff Valve.

- The "Vent" word used in different books should be termed "One-way Valve", i.e., air is allowed inside the fuel system and does not allow to exit for obvious reason (pollution control and fuel loss through vaporization). When engine is running, fuel is being consumed, creating vacuum: the "One-way Valve" allows air to enter the system otherwise there will be vacuum to a point where the fuel pump can't pump against so much vacuum.

- The purpose of the Shutoff Valve is for self-diagnosis. If the ECU wants to check the system for leak, the first thing the ECU does is to shut the outside air from coming: this is EVAP Shutoff Valve's function.
a. If the EVAP Shutoff Valve fails "closed": then will be vacuum in the system (open the gas cap and you hear a "whoooosh"...
b. If the EVAP Shutoff Valve fails "open": during testing air is allowed in and the system thinks there is a leak, but in reality there is no hose leak.

EVAP.jpg

Thanks. That all makes sense now. Excellent description and explanation. You mentioned in a very early post that "vent" was a poor name for the valve and now I understand why. It's an electrically actuated one way vent with integrated check valve.

Mine had the symptoms of being stuck closed (giant whoosh when removing gas cap) for a while and now I have the symptoms of being stuck open. The codes started up again as soon as the whooshing stopped. So based on what you've taught me I still think my evap shut off valve is probably bad. What is hard for me to believe is the fact that it didn't last two years. Maybe the hose came off ... Doubt it though.

Post by **cn90** » 08 Feb 2016, 20:14

Volvo PN 9135805 is about $110-$120 at Volvo dealer.
But I rarely see a bad one in this forum.

What brand did you use 2 years ago?

markjcm · Post by **markjcm** » 09 Feb 2016, 04:03

The shut off valve's default position is open - the computer will only command it closed under certain circumstances to test the EVAP system for leaks.

You can verify proper operation of the valve in a few ways. One is by manually powering the valve (closing it) and using a hand vacuum or hand air pump to check for leakage.