P0456, trouble starting after filling gas tank

[Leo99]

My 2004 Rav4 4cyl has been a little hard to start right after filling the tank with gasoline for the past 2 weeks and today it threw code P0456, P0456 - Evaporative Emissions System - Small leak detected. Been going to several different gas stations.

The gas cap seems fine. The gasket in the gas cap is pliable and soft.

Doing some research, it seems the likely cause is the vapor canister valve or the vacuum switching valve. Are these two vales the same thing? They look rather similar in the pictures. The valve on my engine looks like this: http://www.carid.com/2004-toyota-rav4-em...r-63132108.html

I reset the CEL today hoping it's just the gas cap but I'm doubtful it's just the gas cap but my wife feels less anxiety if the light is out.

I plan to order a vapor canister valve and replace it but I'm traveling out of the country for a week and wont' have time to do this until I get back in a week. These things always seem to happen right before I need to take business trips. I examined all the hoses attached to the canister and they all look fine. Anything else to look at before I throw parts at the problem?

Will filling up to only 3/4 of tank prevent the trouble starting the car?

 

[Robenstein]

My 2006 Scion TC kept throwing similar codes. My gas cap was only 4 years old then and looked fine. I swapped it out anyways, and it fixed the issue.

Try a gas cap if it comes back. They are cheap.

 

[azjake]

Only filling to 3/4 might help, Don't know if you did/do this when filling up, but the one thing you shouldn't do with the vapor canisters in modern cars is pump more gas after the pump has clicked and shut off. That can cause problems.

 

[Eddie]

+1 with the topping up. Ed

 

[147_Grain]

Originally Posted By: Robenstein
My 2006 Scion TC kept throwing similar codes. My gas cap was only 4 years old then and looked fine. I swapped it out anyways, and it fixed the issue.

Try a gas cap if it comes back. They are cheap.

+1

$10 - $12 at Autozone for most vehicles

 

[bvance554]

My sons Passat does the same thing. I also thought not filling it up would avoid the issue but it hasn't. I've put $5 into it and had to let it sit a minute or two before it would start. I never thought the cap could be the issue, but after typing that out it does seem plausible. Maybe i'll try removing the cap for a bit without adding fuel and see if it has an issue. If it does it must be the cap.

 

[Eddie]

When you over-fill repeatedly, you can eventually get the charcoal canister saturated with fuel. When that happens, the trouble starts as the system is only designed to handle fumes.

 

[Leo99]

Originally Posted By: Eddie
When you over-fill repeatedly, you can eventually get the charcoal canister saturated with fuel. When that happens, the trouble starts as the system is only designed to handle fumes.


My wife always fills up and pays cash so in NJ, the gas attendants are always topping off to make the payment an even amount so they don't have to make complicated change.

 

[Warstud]

A simple test with that Vapor Canister is to try blowing thru it. If your able to... it's stuck open and is bad.

 

[dailydriver]

Originally Posted By: Leo99
Originally Posted By: Eddie
When you over-fill repeatedly, you can eventually get the charcoal canister saturated with fuel. When that happens, the trouble starts as the system is only designed to handle fumes.


My wife always fills up and pays cash so in NJ, the gas attendants are always topping off to make the payment an even amount so they don't have to make complicated change.


Tell her to carry coin change and singles with her when she fills up, and to tell them to stop at the first click since she has change.

My son says this also happens to him a lot (he still lives in Joyzee) at his local BP, the last time it actually came gushing out of the filler.

 

[Vikas]

Are we talking about making the payment in the multiple of $10? When gas prices were $0.19 per gallon, rounding up to dollar could overflow the tank. These days, rounding up to single $ does not matter.

 

[Leo99]

Follow up:

Changed out AZ gas cap with a genuine Toyota cap. No change. Stalls after gas and P0456 returned. Changed out the purge valve that is under the hood with Toyota OEM. No change.
Changed out the canister with OEM a couple hours ago. No more stalling after first fill up. Looks promising.

I broke the brackets that hold the two long hoses that I assume are to/from the gas tank. Will try to buy them at the Dealer or have to right something up to hold them up.

 

[Vikas]

Are you talking completely different class of money of the later repair?

 

[demarpaint]

I had a similar issue a while back, this is what worked for me. When the gas pump clicks don't round up too much, stop pumping. EG: If it stops at $20.03 round up to $20.05. I also took a thin film of Super Lube grease and applied it to the gas cap gasket. Doing those two things has resolved my P0455 issue for over 4 years now.

 

[Leo99]

Originally Posted By: Vikas
Are you talking completely different class of money of the later repair?


AZ gas cap: $12
OEM gas cap: $30
Purge valve: $65
Canister: $260

If it was a car that I drove I would have done nothing and just drove it as-is and dealt with restarting once after fueling. But my wife drives it and wanted it fixed so I spent some money to fix it.

 

[philipp10]

bet its the gas cap. My gas cap seal looked perfect, I even tried silicone to help seal it and still got that code. New cap solved it. It was the over-torque mechanism in the original cap. They get weak. BTW, I just bought a $9 aftermarket cap.

 

[Silverado12]

Leo, did the canister include the vent valve? That's a common failure item.

 

[Leo99]

Originally Posted By: Silverado12
Leo, did the canister include the vent valve? That's a common failure item.


Talked a pro and he said it was very likely the vent valve but they don't sell the vent valve on its own; it's only available as part of the canister assembly.