Hot air and gas smell coming in from the cab

[1979SIERRAGRANDE]

  Good evening everyone
 Ive had a difficult summer this year driving my 1979 Gmc c1500 in the heat , mostly because its like 20 degrees hotter in the cab than outside hot air seems to be coming from underneath the dash not from vents most of the time smells like gas I've checked for fuel leaks replaced all rubber hoses this summer as well as the fuel pump. Ive as well inspected the firewall from the engine bay there is some rust but no holes i can see through. I suspect the firewall needing insulation any help or opinions is greatly appreciated also first time posting!

[Irish_Alley]

well your fan may on all the time on a low setting and the blender door for the heat or vent might be stuck or cracked open causing you pull heat from the heater core. one option is unplugging the blower motor or install another switch for the main wire on the blower motor

[gunrac]

 i unplug my fan for summer runnin. ......are you sure your smelling raw gas, or is it exhaust fumes?

[1979SIERRAGRANDE]

its raw gas i redid the exhaust from the header back

[1979SIERRAGRANDE]

I was out working on my truck the other day freshening up the wiring putting wire loom on it as well i redid the ground for the blower motor because it was frayed so i replaced the wire. Turned on the truck to test it and go over to the motor to see if its running just to find out its leaking air out of the heater lines as well as the ac lines going into the ac box . Anyone know or have an idea to replace the cork like OEM adhesive to insulate the ac lines as well as keeping engine fumes out ?I'm thinking this has something to do with the fumes I've been smelling lately.

[1979SIERRAGRANDE]

Hopes this helps to see my problem

[1979SIERRAGRANDE]

ac

[1979SIERRAGRANDE]

heater

[bd]

To reseal the evaporator housing use flexible A/C Insulation Tape.  Any vendor that sells 4 Seasons HVAC products should be able to get it.  Raw fuel odor can be an indication of a fuel hose or line leak, a fuel tank or sender leak, a saturated vapor canister, a bad fuel pump, a leaking fuel cap, etc.  You need to identify the source and get it corrected to avert the potential for fire.

Cooling system heat will melt the A/C tape, so to reseal the heater pipes substitute closed cell foam.

[1979SIERRAGRANDE]

To reseal the evaporator housing use flexible A/C Insulation Tape.  Any vendor that sells 4 Seasons HVAC products should be able to get it.  Raw fuel odor can be an indication of a fuel hose or line leak, a fuel tank or sender leak, a saturated vapor canister, a bad fuel pump, a leaking fuel cap, etc.  You need to identify the source and get it corrected to avert the potential for fire.

Cooling system heat will melt the A/C tape, so to reseal the heater pipes substitute closed cell foam.

I've had the problem since i first bought the truck . Since then I've replaced the fuel pump fuel hoses fuel filter as well as both fuel caps and vapor canister filters and really only gets bad when it gets hot on a hot day.

[bd]

Might be a tank venting problem.  Are the fuel tank caps sealed or vented?  With a carbon canister, they should be sealed.  Have you ever checked the fuel sender o-ring?

[1979SIERRAGRANDE]

Might be a tank venting problem.  Are the fuel tank caps sealed or vented?  With a carbon canister, they should be sealed.  Have you ever checked the fuel sender o-ring?

No i have not if i drive the truck sometimes i used to see the canisters blow out carbon pebbles and cover the fender thats why i decided to change the filters

[bd]

The carbon canister is probably original to the truck and likely saturated.   Since it's spitting carbon granules it should be replaced, otherwise some of the granules may find their way into the carburetor fuel bowl through the vent line and cause flooding or other fuel delivery problems.

[1979SIERRAGRANDE]

The carbon canister is probably original to the truck and likely saturated.   Since it's spitting carbon granules it should be replaced, otherwise some of the granules may find their way into the carburetor fuel bowl through the vent line and cause flooding or other fuel delivery problems.

Can you even find replacement ones these days ? Every squarebody I've come across they either bypass them or throw them out completely

[bd]

Occasionally, they come available.  Post the number cast into the top of the canister.