Fuel tank pressure

[BlueBaron762x39]

There seems to be quite a bit of pressure built up in the gas tank when I refuel it after driving it.  Is it normal for there to be some pressure released on these cars when you loosen the gas cap or does that indicate something is wrong?  This is a 1979 Trans Am with a stock Olds 403.  The charcoal canister and it's associated hoses are all hooked up to the vent and quadrajet carburetor.  My car does not currently have the EGR valve though as I'm having difficulty finding the small part that goes between it and the carburetor in the vacuum line.  The car does seem to be running rich.

[Wallington]

Check that you have the correct vented fuel cap too.

The part between the EGR and the carb is a coolant-heat checkvalve so it operates until car engine warms up only.

[BlueBaron762x39]

Check that you have the correct vented fuel cap too.

The part between the EGR and the carb is a coolant-heat checkvalve so it operates until car engine warms up only.

Is the fuel cap vented in 1979?  I thought it wasn't.  Where can I get a coolant-heat check valve for the EGR?

[Wallington]

vented via pressure valve I meant to say, it may still not be the right type but most are fine. Likewise, return line or similar may be blocked. You don't have any fuel stalling issues? That's another easy sign of struggling fuel pump against an incorrect cap or return lines and struggling to suck fuel, you'd notice that before the cap pressure though!

I have not seen anyone that sells the vacuum checkvalve. It's why I requested a sticky section for California cars but never happened. Because not only are original parts long gone, many don't seem to have an aftermarket alternative, of specific settings anyway.

For interest, '76-78 Olds used the Thermal check-valve #419459 (Dark Green and Black), while '78-79 Olds used #560111 (Yellow and Black) possibly due to revised and tightened emissions setup. I haven't looked for an alternative as I don't use one. These were genuine GM parts but produced by Standard, who did them for everyone.

[BlueBaron762x39]

vented via pressure valve I meant to say, it may still not be the right type but most are fine. Likewise, return line or similar may be blocked. You don't have any fuel stalling issues? That's another easy sign of struggling fuel pump against an incorrect cap or return lines and struggling to suck fuel, you'd notice that before the cap pressure though!

I have not seen anyone that sells the vacuum checkvalve. It's why I requested a sticky section for California cars but never happened. Because not only are original parts long gone, many don't seem to have an aftermarket alternative, of specific settings anyway.

For interest, '76-78 Olds used the Thermal check-valve #419459 (Dark Green and Black), while '78-79 Olds used #560111 (Yellow and Black) possibly due to revised and tightened emissions setup. I haven't looked for an alternative as I don't use one. These were genuine GM parts but produced by Standard, who did them for everyone.

How critical to the operation of the EGR is the thermal check-valve?  Will the EGR valve still work if it is simply connected to the carburetor without the thermal check-valve or will that cause problems as well.

[BlueBaron762x39]

vented via pressure valve I meant to say, it may still not be the right type but most are fine. Likewise, return line or similar may be blocked. You don't have any fuel stalling issues? That's another easy sign of struggling fuel pump against an incorrect cap or return lines and struggling to suck fuel, you'd notice that before the cap pressure though!

I have not seen anyone that sells the vacuum checkvalve. It's why I requested a sticky section for California cars but never happened. Because not only are original parts long gone, many don't seem to have an aftermarket alternative, of specific settings anyway.

For interest, '76-78 Olds used the Thermal check-valve #419459 (Dark Green and Black), while '78-79 Olds used #560111 (Yellow and Black) possibly due to revised and tightened emissions setup. I haven't looked for an alternative as I don't use one. These were genuine GM parts but produced by Standard, who did them for everyone.

How critical to the operation of the EGR is the thermal check-valve?  Will the EGR valve still work if it is simply connected to the carburetor without the thermal check-valve or will that cause problems as well.

I finally managed to find a original NOS GM thermal check valve (the yellow and black #560111) on ebay just now and purchased it.  It looks like I may be missing a metal bracket of some sort that holds the valve to the top of the timing cover.  Does anyone have a diagram or photograph of where and how the check valve is supposed to be installed?  Is there a part number or source for the bracket that is needed to hold the check valve in place?