CamaroSS30thAnn

With no EVAP and big pump my tank likes to build pressure.

Whats a good way alternate way to relieve pressure.

Injuneer

Did you remove the pressure control valve located between the sending unit EVAP connection and the canister? Did you remove the canister? Is the sending unit EVAP pipe sealed off? Have you checked the white plastic vent valve? Is there any evidence the big pump is generating excessive heat, increasing the vapor load?

There are at least two ways the tank can vent excessive pressure. When I removed the canister, I just put a filter sock over the end of the tank hose I pulled off the canister. Resulted a fuel smell at the rear of the car, but at that point it was a “track” car.

http://shbox.com/1/fuel_pump_wiring.jpg

CamaroSS30thAnn

Great response. Very appreciated. I did not remove the canister or the valve. I have not checked the white valve as well. Im ok with some smell in the back. The line is not plugged that i.know of but will check again. Car is driven only a few times a month will see track when it can.

I have no evidence it has to do with the pump other than word of mouth that the bigger pumps can cause more pressure. I also run 58 psi not sure if that has anything to do with it.

I might even wrap the y pipe near the fuel lines in case its heating the fuel up in any way if that has anything to do with it as well.

Anything i can do to check the valves etc?

Injuneer

The pressure control valve between the tank and the canister should open when the pressure in the tank reaches 0.7 PSI. The vapor enters the canister and is adsorbed on the surface of the charcoal. Possibly the pressure control valve is not functioning, or the canister is plugged up preventing vapor from entering. Could be filled with liquid fuel if the tank is sometimes over-filled, the charcoal could have broken down and plugged things up, or because you are not purging the vapor with the EVAP system. I would pull the tank-to-canister line off the canister and see if the pressure issue goes away.

Detail at the bottom of this page from Shoebox shows the location of the tank-to-canister line ("Tank Tube"):

http://shbox.com/1/evap_system.jpg

If the pressure is getting really high, both the pressure control valve/canister problem described above AND the tank pressure/Vacuum relief valve ("Fuel Tank Vent Valve") would have to be malfunctioning. I think the tank vent valve opens at about 1 PSI. In that case, pull the vent hose off the white plastic valve shown in the Shoebox photo I linked in post #2. If that relieves the pressure problem, you have found the items that need to be corrected. I would replace the white plastic vent valve if its defective, because with the hose disconnected, you may get fuel spillage in an accident.

CamaroSS30thAnn

thank you Injuneer i will do both. I found the canister earlier today. I thought it may be clogged but wasnt sure. I will do both as stated and see what happens.

Thanks again.

CamaroSS30thAnn

I removed the EVAP canister and valve.
The valve seems very restrictive. Its hard to blow through. Combine with the can being full of "charcoal" i can see it making difficult to vent without a vac source pulling on it.

I also wrapped my y pipe where the fuel lines crossover.

I ran it for 10 minutes and didnt get any pressure out the cap when opening it. I guess ill have to go for a drive and see what happens.