328 fuel tank pressure / evap control valves

I fueled up my 328 the other day and the tank purged out a bit of pressure when I cracked open the gas cap. I wouldn't say it was a lot, but I can't remember the last time any of my cars did this.

The 328 has an evaporative control system that vents the tanks through a charcoal canister. Inline to the canister is a rollover valve (part # 124193, to prevent fuel leaking out the vent line if the car rolls over) and a two-way valve (part # 114910). The two-way valve is supposed to allow a small amount of pressure or vacuum in the fuel system before it opens to vent (no reason other than emissions). Does anyone have a feel for how much pressure this would be on the 328? Is it normal to notice pressure like that when cracking open the cap?

Both of those types of valves are known to stick when they get old, so I am wondering if one or both of them needs to be replaced. I believe neither are readily available so I'd probably have to substitute something similar. The two-way valve can be removed altogether but I'd just as soon keep one. Problem is, the replacement would need to have similar pressure specs to the original or it would risk putting the fuel system under too much pressure or vacuum. Anyone done this before and found suitable replacements?

When I have time I want to check the whole tank venting system to make sure there aren't any leaks or blockages. The charcoal canister and vapor separator could also be plugged, though it's less likely than the valves.

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Awesome, thanks for the lead, that is a huge help. Yeah, the rollover valve is easier to diagnose and rescue, and I think there are some modern equivalents that would work if the old one can't be cleaned/fixed.

 

OK, thanks, that is a good data point.

 

I really can't remember the last time I noticed this on my other cars, which seems odd now that you mention it.