How to change vapor canister on 1999 rav4 - 1999 Toyota RAV4

Have you changed your fuel cap? That is usually the culprit. If that doesn't solve your issue, a simple smoke test will show you where the system is leaking.

Question edited for clarity.
Question moved to sub category.

https://www.google.com/search?q=1999+Ford+F-150+5.4.+EVAP+purge+vapor+canister+valve+location

..

The charcoal canister is filled with a charcoal type filter that eliminates or absorbs the fuel vapors from the fuel tank and keeps then from getting into the air.

Under car,usually mounted near or in front of gas tank

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwiWp7rZtOfKAhVBlh4KHY1RAwYQtwIINTAG&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DQIlti3aZ22M&usg=AFQjCNEz4TLhC8cVKeIar-IctwksFPqv_g Repair Guides Components Systems Evaporative Emission Control System... https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=0ahUKEwjQ4dL_tOfKAhVCGx4KHaITC3w4ChAWCBowAA&url=http%3A%2F%2Fcommunity.cartalk.com%2Fdiscussion%2F2290225%2F01-olds-alero-evap-problem-getting-choked-out-by-gas-fumes&usg=AFQjCNEyLR6NegYlup_S2N6z_mGccu_DFA&bvm=bv.113370389,d.dmo

Have evap codes? a vapor pressure sensor is part of your canister evap system, located under rear of vehicle.

the canister control valve is mounted on top of the charcoal canister

The tank is vented to the intake manifold when the engine is running, and to a vapor canister when it is not. During hot weather the vapor canister can become overloaded with fumes.
Depending on where the smell is coming from, you could have a leaking vent hose or liquid fuel in the canister.

what codes?

The vacuum lines run from the canister to the intake manifold. One is the purge hose to deliver stored fuel vapor to the intake to be burnd when engine is warm and you are crusing at part throttle. The other line is the vacuum line to operate it.

Fuel Vapor Valve, Aerostar (4.0L Engine) The evaporative emission valve (9B593) uses a small orifice, 1.83mm (0.072 inch), that allows vapors to pass into the vapor line running forward to the evaporative emissions canister (EVAP canister) (9D653). This evaporative emission valve mounts directly into the fuel tank (9002) using a fuel vapor separator seal. Fuel vapors trapped in the sealed fuel tank are vented through the orificed evaporative emission valve. The vapors from the fuel tank leave the evaporative emission valve through a single vapor line and continue to the evaporative emissions canister in the engine compartment for storage.
-----------------------------------------------------
Fuel Vapor Canister Purge Regulator Valve, Aerostar, Ranger Removal and Installation

1. Disconnect wire harness from evaporative emission canister purge valve (EVAP canister purge valve) (9C915).
   

1. Disconnect wire harness from thermistor.
   

1. Disconnect evaporative emission canister purge valve assembly from fuel vapor canister and throttle body.
   

1. To install, reverse removal procedure.
   

-----------------------------------------------------------------

Sounds like a vaccum problem, but I am not sure. It is not vapor locking on you is it? Maybe your fuel pump? A lot of possibilities.

evaporation canister is located under the trunk.