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Discussion Starter · #1 ·
Got a code for a major Evap leak today. Reset it. Came back in about ten minutes.

I have the WIS troubleshooting... but what are the usual causes/suspects on our cars?
 

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Bad gas cap? Had that at least once on a different car when the o-ring got twisted.

I simplified my evap system to remove the line that goes to the turbo inlet, and just found a generic GM check valve to replace the stock one. Makes it easier to diagnose when there are less hoses to deal with in the engine compartment.
 

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Discussion Starter · #4 ·
I figured the Major option meant the gas cap wasn't the cause, but I will give it a shot. Will also look over the engine compartment hoses.

So @Deskmechanic, you disconnected the hose to the cobra entirely?
 

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Yeah I just ran one 6mm/7/32 hose from the back of the tb to a check valve (ACDelco 14047619) and from there to the solenoid. Removed all the other crap, those saab check valves don’t last long and it’s a boost leak if they go. Just go straight from cobra to the APC valve. I think I added an elbow to the tb hose because I didn’t like the way it routed but I’m anal and a straight hose works fine.

the Swedish guys on Trionictuning plumb them that way.
 

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And major leak is the usual one for a loose gas cap or torn vac hose. Minor is a pinhole or something. I think the area equivalent is listed in the WIS somewhere.
 

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Discussion Starter · #7 ·
And major leak is the usual one for a loose gas cap or torn vac hose. Minor is a pinhole or something. I think the area equivalent is listed in the WIS somewhere.
Interesting. I thought the gas cap threw a minor code. I would have checked it right away if I I knew it was a possibility.
 

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Wow, good stuff!! I’m having some sort of fuel problem and I suspect the purge valve but I will post a new thread! I’m glad there are knowledgeable people in here. Maybe I should reroute mine. Thank you for your help in here help guys 👍🏼
 

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I thought T7 actually had a "check gas cap" warning for that particular leak... maybe I'm thinking of newer cars. WIS probably knows. But I think the conditions for an evap leak code are quite specific.
 

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Yeah I just ran one 6mm/7/32 hose from the back of the tb to a check valve (ACDelco 14047619) and from there to the solenoid. Removed all the other crap, those saab check valves don’t last long and it’s a boost leak if they go. Just go straight from cobra to the APC valve. I think I added an elbow to the tb hose because I didn’t like the way it routed but I’m anal and a straight hose works fine.

the Swedish guys on Trionictuning plumb them that way.
This was essentially the mod introduced on the 9-5 from 2006. I did same on my 2004 9-5. For the first tube from evap valve to the (aluminium) NRV I used fuel hose but found it was sucked flat! I didn't appreciate how low the pressure gets in there. It seemed pretty tough tube. Anyway I used a curved section from the original pipe off the evap valve, which is of course rigid plastic inside rubber.

Original question - yes the filler cap gasket is often given as the first suspect. In another car (VW Polo) I just replaced the evap valve with a scrap yard find, which solved it. Apparently they get clogged and the gap past the moving part is tiny. The pic is a Saab 9-5 valve - the valve is the square plate in the frame at right. The electromagnet is at centre. I assumed that shaft in the can at left was the plunger but it had zero movement. Maybe that was the defect. It was a few years ago.....


9-5 evap valve.jpg
 

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Discussion Starter · #11 ·
Doug: Just got back in town so I'll haven't started diagnostics yet. Will be doing it.

Meanwhile, does that valve pull apart easily? If so, maybe we should be cleaning them.
 

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The valves are sonically welded shut. I've heard of some people cleaning them with a shot of carburetor cleaner, like how the idle air control valve is cleaned, but I've never had much luck with that. My 1997 900's purge valve has died twice so far, and I've replaced the purge valve on both of my 9-5s once since I've owned them. The 900 was practically undriveable when its valve went. I think it had failed open and caused unmetered gas tank fumes to get sucked into the throttle body. The 9-5s both seemed to run fine, but had large evap leak codes.
 

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Discussion Starter · #13 ·
I think DeskM wins. I loosened and retightend the gas cap today. Cleared DTC's. Drove over an hour and it didn't come back (whereas I got it back in five minutes before re-torquing the cap).

Odd, as the cap appeared to already be fully tightened (clickity-click). Also, it's been over a half a tank since I filled it and I didn't get a code for the first half tank. But, whadeva. Seems like it might be cured.
 

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I think DeskM wins. I loosened and retightend the gas cap today. Cleared DTC's. Drove over an hour and it didn't come back (whereas I got it back in five minutes before re-torquing the cap).

Odd, as the cap appeared to already be fully tightened (clickity-click). Also, it's been over a half a tank since I filled it and I didn't get a code for the first half tank. But, whadeva. Seems like it might be cured.
Isnt there an O ring in the equation ? Might be worth changing as clickity click should be enough torque ..
 
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