1. Engine compartment fuel odor after car sits for a day. Also rough idle and response smooths out if I pinch the vapor hose from the engine-compartment canister to the intake manifold. Replaced this canister with a salvage unit of more recent vintage. This one is plastic can, not metal, but same three ports. Granules audible when can is shaken. No change in poor engine operation. Reinstalled original canister.
2. check valve(?) in the trunk broke while I was replacing all hoses. Received a replacement salvage part - quality unknown. Can be installed in two orientations, is there a right/wrong? One nipple has black orfice, ostensibly for identification purposes. What is the function of this item?
The Haynes manual has no block diagram or detailed info about the vapor recovery system. Maybe if I knew how the system is supposed to work, I could troubleshoot it better.
The valve is part of the fuel vapor recirculations system, and has 3 modes of operation.
1) Fuel vapors from the gas tank enter the valve thru one of the nipples (let's call A), then exits the other nipple (B), en route to the charcoal cannister
2) As the fuel level in the tank goes down, this valve serve as a vent to allow fresh air into the tank. Fresh air from from the trunk enters the foam filter on the back side of this valve, this goes through an internal 1-way check valve, and on through nipple A, back to the tank.
3) Should the charcoal cannister line ever be plugged, this valve acts as a safety vent to vent excess pressure from the gas tank to the atmosphere (actually, to the trunk -- that's why your trunk smells like gas all the time if you remove the cannister and plug the line).
If you hook up a vacuum line to the the A and B nipples, one at a time, you should only be able to pull vacuum air flow through the A port (you should hear air being pulled in through the foam filter on the back side of the valve). If you try to do so through the B port, it will just act like it is closed off. Connect the A port to the gas tank lines, the B port to the line going forward to the charcoal cannister.
On my car the line from the top of the charcoal cannister is then connected to the intake manifold. However, the intake manifold nipple has a very tiny orifice to only allow a minute amount of vacuum flow. If you are not throttling the vacuum flow through a small orifice, then you are essentially introducing a vacuum leak, which is why the car idles rough until you close off (or mostly close off) this leak path.
All of this information is given in the owners manuals and repair manuals. You may want to put that on your shopping list. I know that they are not always the easiest items to find, but if you watch e-bay, you'll get one before long.
You're in luck! I found a spare one in the garage. The side with the black nipple is the one I called the 'B' side -- it goes to the charcoal cannister. The safety relief valve is right next to it.
The 'A' side gets connected to the vapor recovery line that go to the tank.
I marked the valve indicating flow direction before installing, and it appears that I lucked-out; upon checking today, black nipple does indeed face the canister, so we're OK there.
Returning to the engine compartment, it seems that the PO had attached the canister line to the incorrect, unrestricted nipple on the intake manifold. He capped the adjacent, restricted one in his bypass of the fast idle circuit. I've corrected this, and she idles fine. Hang on to that spare valve for a few days, will you? I'm going to try the original metal canister for a few days; if fuel odor returns, will swap the newer plastic one again. I think we're almost there; its a bitch trying to fix two things at once.
Regardng the manual, I have the Haynes, but thought the factory version was only for '77+. Will revisit this, as I could use additional resources.
