1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Hi, Chris.
I did a little research when I replaced my Evaporative Loss Control Device, or ELCD - which I now call "El Cid." (27 years in the military has twisted my brain into a need for using acronyms!)
Here's what that whole system is =supposed= to do, according to my shop manual. When the engine is off, on a warm day, fumes from the fuel tank are vented into the ELCD, rather than just going directly into the atmosphere. The canister itself isn't sealed (look at the bottom of it) so the fumes basically pass through the charcoal on their way out to the atmosphere. Theoretically, the charcoal captures the fumes as they pass through, so none get out. (Riiiiiight....) That's the reason you're supposed to replace the ELCD periodically, by the way... the charcoal sort of gets saturated and wears out, and then those fuel tank fumes just go right through it. If your ELCD is more than 5 or 6 years old, that's what's happening.
So when you go out and start your car and vacuum is applied to the valve on the top of the ELCD, it opens an internal passage and allows air to pass over the charcoal inside to be sucked into your intake manifold. This air supposedly cleanses the charcoal of the trapped fuel vapor particles, which are returned to your engine and burned with your regular air/fuel charge.
That's the cycle, essentially... capture fumes with engine off, return fumes/fuel vapor to engine with car running (vacuum applied).
So the only reason we have an ELCD in our cars is to reduce that intolerably hideous gas tank smell the car would otherwise have while standing still. Personally, I've never noticed a strong fuel stink coming from my car, even when I left the original equipment ELCD in there for 13 years and over 150,000 miles. I don't think this concept of capturing fuel tank fumes is such a big deal; I've never noticed any fuel stink from ANY cars unless someone replaced a missing gas cap with a rag... the Molotov Auto Conversion. In the old days, we used to have ventilated gas caps on cars and unless you went sniffing around the gas cap, you didn't notice. (Admittedly, my nose may be desensitized in this regard, having spent a lot of time around jet aircraft.)
Your ELCD, Chris, is obviously a problem, and I think I know why. The small vacuum hose going to the top of it is a "control line" which operates a moving diaphram inside. Essentially, it's just supposed to open and close a valve to let the vapors from the can into your engine through that bigger hose. Your diaphram is apparently punctured or torn, and when vacuum is applied, it's becoming a vibrating noisemaker. It's also a vacuum leak, which is why the car idles poorly with it connected.
I believe you have 3 options:
1). You can get a new one from one of the TSN sponsors, like SobStory, for around $50 or so. I did that last fall. (It lasted about a week before the diaphram broke again. Hopefully, you'd have better luck.)
2). You can attempt to repair the diaphram. Don't ask me how, but someone just suggested a rubber tire patch would do the job.
3). You can just plug the vacuum lines going to it and thus remove it from your system. Eventually, the charcoal inside will become saturated with fumes and then you may notice some fuel stink coming from it. If you're in the habit of sticking your head down there next to the ELCD to breathe, this could be a problem, but otherwise, I'm guessing you won't notice it.
By the way, my wife, who can smell the sweaty gardener across the street from INSIDE our house, has never complained about any gas fumes in our garage coming from my Saab. The lawnmower actually stinks a lot more, if that helps you put it in perspective... it doesn't have a charcoal fume filter on it. Neither does my pressure washer. After replacing the ELCD on my Swedish Beastie and having it fail within days, I've decided I'm never going to do it again, for what that's worth to you.
Hope this helps. Best regards,
- = M = -
'87 900T 165K
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