The evap emissions system has nothing to do with setting the air/fuel mixture. If you mount the evap canister more than 36" away from the tank it will take the LD pump too long to pressurize the system. That will be interpteted by the PCM as a minor leak.
Originally Posted by waynehartwig
I've done more checking this morning about this, and it appears the only time the canister is utilized is when fueling. The canister holds the vapors so they aren't put into the atmosphere. Then when you start it, they are purged (brought into the intake side and burned with the normal fuel/air mixture).
Having the book is easier. It's right in there in black and white.
From the '03 FSM:
The evaporation control system prevents the emission of fuel tank vapors into the atmosphere. When fuel evaporates in the fuel tank, the vapors pass
through vent hoses or tubes to a charcoal filled evaporative canister. The canister temporarily holds the vapors. The Powertrain Control Module (PCM) allows
intake manifold vacuum to draw vapors into the combustion chambers during certain operating conditions
. (Bold letters by me. It doesn't say start up. It says certain operating conditions, whatever they are.)
However, I don't see anything that confirms that this setup is used as fuel trim.... I was told this by a Jeep tech. I have learned that that whole setup does leak checking on the gas tank. It pumps it full of air (pressurizes it) and then waits for the air to bleed off. If it fills up with air too fast, it calls a code becuase it's blocked. If the pump cycles too often, or never stops, it pulls a code for a leak.
From the '03 FSM:
The evaporative emission system is designed to prevent the escape of fuel vapors from the fuel system (Fig. 9). Leaks in the system, even small ones, can allow fuel vapors to escape into the atmosphere. Government regulations require onboard testing to make sure that the evaporative (EVAP) system is functioning properly. The leak detection system tests for EVAP system leaks and blockage. It also performs self-diagnostics. During self-diagnostics, the Powertrain Control Module (PCM) first checks the Leak Detection Pump (LDP) for electrical and mechanical faults. If the first checks pass, the PCM then uses the LDP to seal the vent valve and pump air into the system to pressurize it. If a leak is present, the PCM will continue pumping the LDP to replace the air that leaks out. The PCM determines the size of the leak based on how fast/long it must pump the LDP as it tries to maintain pressure in the system.
Bottom line, I think I would be safe to remove the canister - unless local smog laws require it's use. But as for safety and operation, I shouldn't have a problem later. However, when I fill up with fuel, the fumes will be escaping to the atmosphere...... But this does make it easier than relocating everything
Not if you do what I did. It's still a closed loop. No fumes escaping to hurt the whales, kill the baby seals, denude the rain forest or contribute to global warming.
I have not seen any negative effects. If and when I do, I'll mount the canister under the tub and hook it up.