So I noticed my 94 Ciivic was leaking gas from somewhere under the engine. The car started running like crap, exactly like it did one other time . I pulled over and I could smell raw gas, then I saw a small trail of gas that followed where I drove the car. I poked around for about 15 minutes until I noticed the bottom of the vapor canister was leaking. I tried turning the canister upside-down to stop the leak, then I tried driving off. The car would barely run, and stall if I tried to move. I got back out, turned the vapor canister back over and tried driving again. The car ran properly this time so I just drove home. Do I have a problem with the canister or solenoid that would cause the canister to leak and, apparently, cause the car to run like crap at random times?

 

For my 6th gen Civics, the fuel filter is located directly above the canister. If your 94 Civic is the same, then I think a gas leak from a fuel filter connection is a better bet.

 

As the name suggests, there should never be liquid fuel in the canister, only vapors.

It has a pipe back to the fuel tank with a "two way valve" mounted near the tank. The vapor recovery system acts when the pressure in the tank rises enough to overcome the valve, the excess vapors are directed into the canister and absorbed until the next time the car is used. When the engine is above idle speed, the solenoid opens and allows the canister to be purged. Air enters the bottom of the canister and gets pulled into the manifold by vacuum. Thus the trapped vapors are slowly burned off in the engine. All of this is done because raw gasoline vapors released into the air will become smog.

None of this system should have any effect on fuel flow to the engine. There's entirely separate plumbing for that. Maybe the lines on your car are hooked up improperly. If the engine is running badly and black smoke is coming out, that is likely because the fuel pressure is too high (it could also be a stuck injector). Fuel pressure could rise because the return line to the tank is blocked or the regulator is bad. A bad regulator can also leak gas out to its small vacuum line, which will flood the manifold.

 

There was definitely no leaking from the fuel filter, that much was pretty easy to determine. Whatever was leaking, it was dripping onto the exhaust pipe, running down the pipe a bit then onto the ground. I'll check out the vapor canister tomorrow.