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Saab Model 99 Bulletin Board
1969-1984
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Related - the evaporative emission system
Posted by Gary Stottler (more from Gary Stottler) on Fri, 4 May 2012 05:13:21
In Reply to: the exhaust ports have short tubes in the manifold -, jimmy, Thu, 3 May 2012 19:47:21

While we're on the topic of '70s emissions controls, you mentioned removing the line to the charcoal canister from the filler neck. That is actually part of the evaporative emission control system designed to capture fuel vapor from the fuel tank and burn it in the engine rather than releasing it into the air. Saab did this on 99s by making the fuel tank hold a lot of pressure (that "whoosh" when you take the gas cap off). One result is that there's always a small vapor leak somewhere and so 99s always smell like gas inside. What I hope to do on mine is eliminate the device that caps that pressure, let the tank freely vent into the canister, and then let the engine pull the vapor out of the canister when it's running. It might not meet the emission law, but at least I wouldn't have gas smell in the car all the time, so the air quality in there would be better :-). Letting it vent to atmosphere directly is another way to do it, however, keep in mind that there's a "rollover valve" in the vent line that you might want to keep - that keeps the fuel in the tank when you get the car upside down....

The PCV is "Positive Crankcase Ventillation" - the black 3/4' (or metric equivalent) that runs from the bottom of the airflow meter housing up to the nipple on top of the valve cover. You really don't want to remove that - it's needed to pull moisture out of the crankcase which is important to prevent internal engine corrosion and sludging ala 9-5 engines!

Just 2 more cents - can you tell I spent many years in the emissions development group?

Gary

posted by 198.208.15...

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