Trying to diagnose a trouble code on 98 s70. The code from generic OBD reader is a po172 which converts to a volvo code of 231 or 232 according to my mitchell manual. After making a few checks I found the hoses to the EVAP valve a little crumbly but I don't think they were leaking. Next I placed a hand vaccum pump on the manifold side of the valve and it would not hold a vaccum. It slowly leaked down. Does anybody know if it should hold steady or does the valve have a orifice that lets it draw a small amount all the time? Also in the past I've had a po455, converts to 611, Seems like the two may be related.

 

Yes the 2 would be related.Put the vaccum pump on the other side of the valve opposite of the manifold.
It should hold vaccum.Thats how the ECM determains if there is a problem in the system.
Look in the back by the fuel filter there is another valve there that the vaccum line cracks sometimes.
If not try to put some air to the system instead of vaccum.It has to be very little air.But then you can spray the hoses with soapy water to find the leak.
Also check the plastic line where it goes down from the valve and across the subframe.Sometimes when people bump the parking stops it will cut the hose.

 

TECH> Thanks for the reply. I vaccum tested from the EVAP valve back to the tank and it wouldn't even pump down so I'm sure that line is open somewhere. I'll inspect that portion of the line today. But how about the EVAP valve? Should it not hold vaccum on the manifold side? It's not completely open but it will leak all the vaccum in about 5 seconds.

 

That should hold vaccum as well unless the car was shut off while the valve was open.
The evap valves are another known fault on the 1998's.

 

TECH>OK I've tested the line from the evap valve back to the canister. I've got a pressure regulator on my air compressor so I was able to set pressure to 10 psi. Took the line off of the evap valve and put the air to it. I could hear it blowing in to the canister. I took the line off of the canister and plugged it and then my air hose blew off the other end so I'm sure it is good. Maybe I've misunderstood you or didn't make myself clear,But shouldn't the line between the evap valve and the canister be open to draw vapor out of the canister when the evap valve is opened? When I hook a vaccum pump to the line going back to the canister it should draw no vaccum, I think. Correct me if I'm wrong.

 

TECH> I think I've been wrong about the evap vlave. I think I'm looking at the canister purge valve. Located next to the radiator on the drivers side.

 

There is a big line at the canister pinch it off with a pair if vise grips.Then put pressure on it.You might want to turn the air down a little lower as well.It should not have any leaks.If it blew the hose off the other end then it should have been holding pressure.
Another place that these cars develop a leak is on the top of the tank.There is a line there as well that will leak.

 

I finally figured out where the flow of air is going. It's coming out of a hose/filter up by the fuel filler tube. I can stop it up and the fuel tank will start to swell with pressure. So can I conclude that the valve by the canister is stuck open?

 

If you crimp the big hose coming off of the canister and let the tank swell a tiny bit and try to hold pressure will it?
If not then follow to find leak.If the hose is no crimped it should leak some.The tank pressure never gets that high in the system on its own.

You might have a bad charcoal canister.

 

The leak is flowing through the valve that is above the charcoal canister. Is it supposed to be open? I can't see how it is a sealed system if vapors can pass through it. What is the name of that valve?

 

I forget what it is called I don't think it is a rollover valve.Are you sure the hose isn't cracked where it is hard to see it?

 

I think I see where the rollover valve is. This valve I suspect is stuck open has two wires going to it. It seems to me like the way it would work would be to allow air in to the system at certain times I just don't think it would all of the time. I'm going to check around the internet tonight and see if I can get a better understanding of How the whole system is supposed to work.

 

Ok I will see if I can find anymore Info as well.

 

Akbar, what was it at the end, what did you replace? I have CE light, scanned it and it is p0172 and p0455. Looks like the same problem you had, just wonder what did you do?

 

Ok, it seems like Akbar is not here any more, tech what do you suggest, where do I start?

 

Pitar> No I'm not gone. I've not done anything about my problem. I plan to replace the canister purge valve or maybe it's the EVAP valve. I used to be an auto mechanic 20 years ago an I have some understanding of how things are supposed to work and what they're called. I'm pretty sure that the valve located on the drivers side of the radiator fan cowl is leaking and it shouldn't. I will eventually replace it and see if it eliminates the CE light. But if you read all of the post the valve I question is above the evap canister and goes to a filter that is above or about the fuel filler hose. On my car this is open to the atmosphere and I don't think it should be. Afterall, how can it be a sealed system if it's open to the atmosphere. The reason I've not pursued it any further is because the car is running great and getting great gas mileage.

 

Im not sure I understand what you are saying here.If the hose leads no where then something might be disconnected.

 

Tech> If you follow the big hose from the evap canister to the electically controlled valve above the canister then from that valve on it goes up by the fuel filler hose and makes a u turn back down and it has a filter on the end of it. This is on my 98 S70. I think the purpose of this valve is to allow air into the tank in the event of a vaccum in the tank and to also allow a flow of air through the canister when the purge valve is open. I sure wish I had access to a shop manual that might explain it all. My Mitchell manual doesn't do a good job.

 

I will see if I can find any pics of how the system works.

 

that would be great. thanks tech!