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Discussion Starter #1
Has anyone ever had this happen with their Camino? When I go to fill the tank wth gas, once I get home and park the car, a few minutes later I'll start to see gas dripping behind the left rear wheel well. When I open the gas filler door, I see the gas coming right out of the tank and dripping through the gas cap. If I take the gas cap off for a few minutes it seems to stop, then when the gas cap goes back on - it starts dripping again. I can't figure out why or how the gas is going up the tank to the filler location and leaking. Maybe if I had a new gas cap, it would seal it in?

Any suggestions?
 

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While the fuel system is a relatively sealed system it is not a completely sealed system. The tank has to breath and does so through the evaporative systems. There is a Vapor line coming off the tank and is connected to a Charcoal canister under the hood on the left side. If this line is blocked or if the canister has bad valves (needs to be replace) it is possible that could cause your problem. During off operation the canister serves to trap gasses before they enter the atmosphere and during operation that canister serves as a source of slight vacuum sending stray fumes through the carb to be burnt. The gas cap is a sealed cap. it is not suppose to let air/fuems out, liquid, well that is strange indeed. To me.

So if I had to venture a guess I'd say you have a plugged line or a bad canister and very possibly a bad cap. If you smell gas fumes then I'd go for the canister or vapor line.

I looked in my service manual for 78 and it doesn't have anything on fuel coming out of the tank unless the tank has collapsed or is leaking from the filler neck to tank or out of the sending unit cap or one of the lines are broken.

It is possible that somehow you have a pressure build up inside the tank. A bad check valve or miss-routed vacuum line. That leads me to think that the line is plugged or the Vapor Canister is bad. It has those vacuum valves on it inside and is suppose to evacuate the tanks fumes once the truck is running (Creates Vacuum inside the tank). Like I said the Vapor line from tank to canister has nothing on it that turns on or off just a straight open line to the tank.

If it does it again, once it starts remove the line to canister connection, see if it has pressure behind it when you remove it. Pinch the line and hold it next to something so that you'll be able to see or feel any air being forced out when you unplug the line.

However I suppose it could be that cap it is suppose to be a one way unit. Allows air in but not out. During emissions testing they remove the cap and pressure test it. If it doesn't hold pressure it will fail emissions testing.

The outermost lines are connected together and to the PCV then the carburetor port. One inside line goes to the EGR Temperature control valve and then the EGR. One side of the EGR TVS goes to the carburetor. the opposite inside line goes to the carburetor (Center front port on stock 4bbl) the center line goes to the tank.

This is factory stock 305 hose routing for a 78 FWIW.

Hope you find it let us know.
 

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Discussion Starter #3
Thanks

Pete,
Thanks for the detailed help. I'm going to try your suggestions. I definitely think the gas cap at the filler door needs to be replaced. We'll see about the canister and the lines.
 
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