Why does gas pour from vacuum canister when you try to start the car?

I suspect you are OVERFILLING your tank...

There should be a direct connection from your canister to the top of the fill tube. It is intended to safely draw out gas fumes.

even if you don't OVERFILL... gasoline can expand (coming from the cold ground... into a nice warm car) enough to repeat the symptoms you have depicted.

Try putting in less gas...

Things will most probably resolve themselves... otherwise you might need a new canister.

Be safe... DO NOT OVERFILL.

Possible causes
- Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking
What does this mean? Tech notes
The P0455 it's a very common code, because the code is set if the gas cap is loose or missing. Start by tighten the gas cap and clearing the code. In most cases the code can be clear by disconnecting the car battery for about 30 minutes.
What does this mean? When is the code detected?
Evaporative Emission System (EVAP) control system has a very large leak such as fuel filler cap fell off, EVAP control system does not operate properly.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Possible a noticeable fuel odor caused by the release of fuel vapors
P0455 Mitsubishi Description
This diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using engine intake manifold vacuum. If pressure does not increase, the Engine Control Module (ECM) will check for leaks in the line between the fuel tank and EVAP canister purge volume control solenoid valve under the following vacuum test condition.
The vacuum cut valve bypass valve is opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP canister vent control valve will then be closed to shut the EVAP purge line off. The EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line using intake manifold vacuum. After this depressurization is implemented, the EVAP canister purge volume control solenoid valve will be closed.

Read more: http://engine-codes.com/p0455_mitsubishi.html#ixzz3NlVyARyX

Possible causes - Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking The P0455 it's a very common code, because the code is set if the gas cap is loose or missing. Start by tighten the gas cap and clearing the code. In most cases the code can be clear by disconnecting the car battery for about 30 minutes.

When is the code detected? EVAP control system has a very large leak such as fuel filler cap fell off, EVAP control system does not operate properly. Possible symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Possible a noticeable fuel odor caused by the release of fuel vapors P0455 Buick Description This diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using engine intake manifold vacuum. If pressure does not increase, the Engine Control Module (ECM) will check for leaks in the line between the fuel tank and EVAP canister purge volume control solenoid valve under the following vacuum test condition. The vacuum cut valve bypass valve is opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP canister vent control valve will then be closed to shut the EVAP purge line off. The EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line using intake manifold vacuum. After this depressurization is implemented, the EVAP canister purge volume control solenoid valve will be closed.
if tightening the cap or replacing the cap does not help take your car to a shop to have it diagnosed as it requires special tools/equipment to test this and get an accurate results to find what needs replacing.

Try choking it or pumping the gas, possible vacuum leak, or choke not set correctly, carb may need to be adjusted, give more detailed question for more detailed answer. Good luck

P0442 and P0456 are both evaporative emission error codes due to a small leak. The most common cause is a leaking gas cap or hose leak on that system. I did not list a code for your 0513. I am sending you a little information about your problem.. Best of Luck to you..


2003 Lexus RX300 3.0L 2003 Toyota Sienna 3.0L 2003 Toyota Highlander 3.0L, Eng Cfg V6, Eng Des 1MZFE, USA/Canada 2004 Toyota Avalon XL 3.0L
Check engine light is on with trouble codes P0442 and P0456. The codes are evaporative system small leak codes.
1. Verify that the gas cap is a factory Toyota gas cap and visually inspect that all hoses and lines are tight and connected.

2. Locate the canister closed solenoid and the vacuum switching valve on the canister. Manually ground them and verify that they operate and function. The canister closed solenoid is normally open and should close when grounded. The vacuum switching valve on the canister is normally closed and needs to open when grounded.

3. Verify that the hoses are not loose or pulled off the canister closed valve on the air cleaner housing. This has been a common problem on some models.

4. If no problem is found, the next step is to ground the canister closed solenoid and the vacuum switching valve under the vehicle and simulate an evaporative test and verify that the system holds a vacuum and functions normally. When the solenoids are grounded, back probe the Blue/Black (L/B) wire on the pressure sensor, and with no vacuum or pressure, the voltage should read around 3.3 volts. Start up the vehicle and turn on the purge vacuum switching valve and use engine vacuum to draw down the system to around 2 volts on the pressure sensor. If the voltage does not increase rapidly, there is no problem. If the voltage increases quickly, look for the leak in the evaporative system. Potential Causes: Canister Closed Valve
Disconnected Canister Closed Valve (CCV) Hose
Gas Cap
Harness
Vacuum Switching Valve - For the pressure sensor.

Sounds like a vacuum leak at the canister or vacuum lines, lift the hood, start the car and listen for a hissing sound after it warms up, on the fender/frontend area there should be a black canister with vacuum hoses connected, check all the hoses end to end for leaks, there is a vacuum that is created in the tank that is controled (vented gas cap), if there is no vacuum in the canister to the fuel tank, this will cause the check engine light to come on (faulty gas cap). vacuum leaks cause the RPM to increase, I am surprized that's the only code you have. most cars have a diagram under the hood of the emissions.

It's hard to find these small leaks. If you have a vacuum pump, there are a few tests you can run on the components of the system. See below.

TESTING

Vapor Canister
See Figure 1

1. Apply a length of hose to the lower tube of the purge valve assembly and attempt to blow air through it. There should be little or no air should passing into the canister.

If the canister is equipped with a constant purge hole, a small amount of air will pass into the canister.

1. Using a hand-held vacuum pump, apply a vacuum of 15 in. Hg (51 kPa) to the control vacuum (upper) tube. If the vacuum does not hold for at least 20 seconds, the diaphragm is leaking. Replace the canister.
2. If the diaphragm holds vacuum, attempt to blow air through the hose connected to the PCV tube while vacuum is still being applied. An increase of air should be observed. If no increase is noted, the canister must be replaced.

Fig. Fig. 1: Cross-section of the vapor canister


Fuel Tank Pressure Control Valve

1. Attach a length of hose to the tank side of the valve assembly and try to blow air through it. Little or no air should pass into the canister.
2. Using a hand-held vacuum pump, apply vacuum equivalent to 15 in. Hg (51 kPa) to the control vacuum tube. If the diaphragm does not hold vacuum, the diaphragm is leaking. Replace the valve.
3. If the diaphragm holds vacuum, attempt to blow air through the hose connected to the valve while vacuum is still being applied. Air should pass. If no air is noted, the valve must be replaced.

Thermostatic Vacuum Switch

1. With engine temperature below 100°F (38°C), apply vacuum to the manifold side of the switch. The switch should hold vacuum.
2. Start and continue to run the engine until the engine temperature increases above 122°F (50°C). The vacuum should drop off.
3. Replace the switch if it fails either test.

purge valve location:




EVAP vacuum switch pic:



EVAP system diagram:

SCAN IT SOUND LIKE IDLE SPEED CONTROL PROBLEM.BUT I AM LOOKING AT VACUUM LEAK AT THE INTAKE MANIFOLD BROKE VACUUM HOSE. OR FUEL INJECTORS SEALS LEAKING.

fumes from evaporating gas in your tank are captured and absorbed by a canister rather than being vented to atmosphere as they used to be ... when you start the car it purges the fumes from the canister and directs them into the intake manafold where they are burned with normal gas ... often over filling the tank can cause gas to flow into the canister instead of just fumes .. this may, in time,fix itself if you avoid overfilling the tank unless there is a failure somewhere in the evaporative emission control system ..(vacuum hose, solonoid, gas cap and such) .. a bad, loose or leaking gas cap can cause a problem by allowing air to leak into the canister ..

lots here
try the filler neck to see if there are rust spots, then try gas lines, also could be the evap canister, then there are more.....
but start with those, they are the easiest