Does any one know how much pressure should be coming out of a vapor line on a 87 Camaro (5.7L, TPI) when the tank has a lot of pressure and the fuel tank pressure control valve is disconnected? Mine has a mild and gentle flow which can felt only when my finger is in front of the rubber hose. Is this due entirely to the built in vapor restriction or is my line partially blocked?
Thanks, Randy

 

Having the tank pressure control valve disconnected may cause tank pressure to run higher than normal. The tank pressure control valve opens with engine running and allows vapors/pressure to vent through canister. If the valve does not open, the vapors flow to canister through a ristriction in the valve which is intended to keep more of the vapors in the tank when the car is parked. I would recommend you consider reconnecting the valve so that the system can work the way it was designed.

 

I am not running the system this way but simply testing the line as part of my trouble shooting for intermittent gas smells and high tank pressure as in other posts.

 

Okay, now you know that the high pressure youre seeing at the vapor line is caused by the tank pressure control valve being disconnected. As far as your fuel odor is concerned, carefully inspect the fuel and vapor systems for any sign of a leak.(cracked hoses, etc) If you can access a smoke machine, use it to leak test the vapor system and upper tank. It may be worth paying to have it tested.

 

OK, Thanks. I did all of that first. The vapor canister has no leaks and a new filter; purge solenoid assembly, pressure control valve and purge valves are functional. The manifold vacuum is fine and the hoses are new. The ECM control line to the solenoid valve goes low when it's suppose to which is why I was checking for blockage in the vapor line.

 

Restriction at the PC valve is normal with no vacuum applied. Be sure that it is infact openning as it should with vacuum and perhaps check the hoses to and from it for restrictions. Canisters rarely leak but they do become saturated or otherwise contaminated. Replacing the felt at the bottom does almost nothing to improve the canister's performance. The felt only traps large particles. The activated charcoal still becomes contaminated over time. Water and liquid fuel still intrude.

A quick test I have used many times is to check the weight of your canister and compare it to the weight of a known good part. A new canister weighs very little. I have found differences of a few pounds in badly contaminated canisters. If your canister feels heavy when held in your hand, its probably contaminated. The contaminated charcoal does not absorb vapors and those vapors pass through the canister causing fuel odor.

 

Just to make sure were on the same page (because from your last post it looks like we may be talking about different things), the mild and gentle flow from the vapor line that I am talking about in the first post is straight from the tank with the tank pressure control valve totally removed/disconnected from the vapor pressure line, not through the tank PC valve with the vacuum line disconnected. You said this is normal (due to the restriction built in to the vapor line) when there is high tank pressure. Correct?