Hi, I am new to the forum and this is my first post. I recently purchased a 1987 Camaro Iroc 5.7 TPI with a 700R4 transmission sand 73000 miles. Everything on it is original. Never been modified in any way. I purchased it in february and drove it home (about 50 miles). Everything went fine. I have since changed out the tranny fluid and rear end fluid. It has always had no issue starting or anything of that sort. When I started it up to get it up off the ramps for the transmission fluid change today and out for my first real drive, I let go of holding the key to the starting position about a half second short and had to try it again and it had issues starting. I drove it about 15 miles and parked it. No issues. I took it out on the highway and about 10 minutes later i started to smell fuel. Upon getting to my destination I noticed there was fuel pouring out of the evap canister. I shut the car off and it didn't slow down. I quickly headed home. Anytime i slowed down i would leave a large puddle under my car. When i got to my house i shut the car off and it was still pouring out. I unscrewed the fuel tank cap and it released a lot of pressure/vacuum. (not sure which way the air was headed). Started it back up and drove it 1 minute, and had the same issue. Releasing the pressure from the fuel tank made it stop again. The fuel tank was filled at the beginning of the first trip. By the time i was done i had less than half a tank.

I am thinking it may be the canister purge valve as that was the only line going into the canister that appeared to be wet with fuel. Is there any trouble shooting I can do before I just start replacing parts?

 

Check the pressure tank relief valve. It's by the driver side rear axle. If it clogged it won't work releasing pressure from the tank. It's a 2 way valve. Mostly letting air in as fuel is fed to the engine but it does work letting vapor out under heavy pressure. I had to take mine apart and clean it. Don't use any harsh chemicals , just soap and water. Let it dry before placing it back in the system. Also could be the sending unit as the return is right there as well. I'll bet though it the valve not opening and the returned fuel has no where to go from the pressure lock. So it escapes to the closest exit, which is the fuel vapor canister line right next to it in the sending unit.

 

There's a fuel tank over-pressure vent below the filler neck area under the car alongside where the pickup connects to the body hard lines, etc. Check that for blockage and proper operation.

I just deleted mine. Open to atmosphere works well for me.

Rick

 

It is possible that the return and vent lines got switched. This is back by the tank and is easy to do when swapping out the fuel pump.

The vent line on the sending unit is at the top of the tank. While the return line goes to the bottom of the tank. Swap them and tank pressure forces fuel into the canister.

RBob.

 

Thanks for the info. i took it out and cleaned it. Didn't seem to be that bad inside. It definitely should have opened. That spring doesn't seem very strong. I will put it back in and see what happens. Another question. Can I get this all sorted out first and then buy a new charcoal canister or will the rest of the system continue to be messed up now that my canister has been full of fuel?

 

Is there any way to verify this without dropping the tank??? I really don't think it has had a new fuel pump. Everything looks pretty much untouched.

 

I should just be able to blow air in the vent line to the canister and if i hear bubbling in the tank then thats probably the case. Does that make sense?

 

Yes, that is a valid test.

RBob.

 

I just thought of another possibility, it came from someone here that had the same issue. On their car the rubber hose between the pump and sender was leaking and spraying fuel directly into the vent line.

With a 1/4 tank of fuel, hot wire the pump on and listen at the filler neck for a shower like sound.

RBob.

 

My carb car started sucking charcoal out of the cannister because the diaphram inside of it had torn.