EVAP system
05-27-2015, 03:27 PM
#1
EVAP system
Posted a while ago about a gas smell in the cab when the AC is running and most suggested re-torquing the spark plugs since I had just replaced them. Did that and the smell was still there. I'm starting to think the smell is related to me accidentally overfilling the gas tank the day after I changed my plugs. I read that I could've accidentally flushed gas into the actual charcoal canister that holds the vapor for burning. Also read I could've possibly damaged the solenoid that releases the vapor into the engine to be re-burned. Are both of these possible? How would I go about replacing the charcoal canister? Do I need to buy a new canister or can I just flush the one I have out? Thanks.
05-28-2015, 09:05 AM
#2
LightningRod
Doubt its a problem
[MENTION=204429]yknot[/MENTION]
Yes, overfilling your tank can result in swamping in raw gas getting in the vent tube and back to the charcoal canister. But one (or a few) occurrences should not "ruin" anything. The purpose of the EVAP canister is to absorb/hold hydrocarbons and give them up to the engine intake as it can. IMHO you did not harm the "purge" solenoid, or the "vent" solenoid which relieves excess pressure from the tank as fuel in the tank expands. (gasoline has a surprisingly high "per degree" expansion coefficient). This is normal - and "could" possibly explain the gas smell. However, I would also carefully inspect everything to do with the fuel rail and injector ports for any signs of leaks. (injector seals occasionally leak) Otherwise give it some time (without overfilling) and see if it goes away. Also, this situation can cause regular diagnostics tests performed by the PCM to fail and cause a CEL. If so, don't be alarmed, you can run with it for a while and see if it corrects itself when the charcoal gives up all the hydrocarbons.
Below is a very good description of the EVAP system operation that I found:
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The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent solenoid to the atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the PCM will command the EVAP purge valve open, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent valve open, fresh air will be drawn through the valve and vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge valve into the intake manifold to be consumed during normal combustion. The EVAP system requires the PCM be able to detect a leak as small as 0.040 inch in the EVAP system. The PCM uses several tests to determine if the EVAP system is leaking.
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Good luck
Yes, overfilling your tank can result in swamping in raw gas getting in the vent tube and back to the charcoal canister. But one (or a few) occurrences should not "ruin" anything. The purpose of the EVAP canister is to absorb/hold hydrocarbons and give them up to the engine intake as it can. IMHO you did not harm the "purge" solenoid, or the "vent" solenoid which relieves excess pressure from the tank as fuel in the tank expands. (gasoline has a surprisingly high "per degree" expansion coefficient). This is normal - and "could" possibly explain the gas smell. However, I would also carefully inspect everything to do with the fuel rail and injector ports for any signs of leaks. (injector seals occasionally leak) Otherwise give it some time (without overfilling) and see if it goes away. Also, this situation can cause regular diagnostics tests performed by the PCM to fail and cause a CEL. If so, don't be alarmed, you can run with it for a while and see if it corrects itself when the charcoal gives up all the hydrocarbons.
Below is a very good description of the EVAP system operation that I found:
--------------------------
The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent solenoid to the atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the PCM will command the EVAP purge valve open, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent valve open, fresh air will be drawn through the valve and vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge valve into the intake manifold to be consumed during normal combustion. The EVAP system requires the PCM be able to detect a leak as small as 0.040 inch in the EVAP system. The PCM uses several tests to determine if the EVAP system is leaking.
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Good luck