P0456 / Smoke Test Help!

Thanks for looking at this thread. I've done a pretty deep dive on all the p0456 content I could find on this forum, and I still have a couple questions as I've been chasing a p0456 CEL that popped up a few months ago for the EVAP system.

Background: I'm a DIY-first guy who isn't afraid to try several things I see on youtube and this forum, but I'm not an experienced mechanic. Here's what I've done so far, based on what seemed to be the common issues online:

• New gas cap (CEL still on, cleared code)
• Replaced the purge valve (CEL still on, cleared code)
• Used a smoke tester, saw that smoke was pouring out fairly heavily from the filler neck. Replaced filler neck assembly with a new OEM unit (CEL still on, comes back on after clearning)

This morning I ran another smoke test, and there is still smoke coming from two places (see pics) :

1. Looking from outside of the truck (at the gas cap), it's smoking from under the fill neck tube. (it doesn't appear to be coming up from inside the fill neck itself, the gas cap blocks that, but from actually under the metal lip).
2. From under the truck, looking up at the filler neck, it's smoking from a couple orifices (vent tubes?)

This is my first-ever try at a smoke test / EVAP CEL, so I'm at a loss as to what should be happening.

Should there by ANY smoke coming out at all from the gas cap / filler neck area? If not, then I wonder if I got a faulty new gas filler assembly. It's not leaking smoke from any of the couplings where the filler neck tubes hook up to the rest of the truck.

Anything else you'd recommend trying?

Next stop is the mechanic if I can't solve it, but I'm hoping to avoid that with some strong Tundras.com advice.

Thank you!

 

Any body knows the answer? I have a similar problem.

 

By the way? Where did you attach the smoke test tube?

 

There should not be smoke coming out of anywhere IFFF the vent valve is closed. That is the point of the test. To see where the leak point is. However, when the car is shut off, the system is no longer sealed! It must be able to vent pressure, lest your gas tank explodes. The system is pipped to the charcoal canister and then to a vent line that terminates in the area you are seeing smoke. The charcoal absorbs the fuel vapor before the air is released to the atmosphere. In order to find a small leak, you need to either close the vent valve via a bi directional code reader or block the vent line somehow. You do however need to leave the vent open long enough to fill the system with smoke before closing it.

 

I see! So the vent holes around and under the cap are open when the car is turned off so if I enter smoke in the line it would indicate a leak with engine shut off. I need to look further in this case. So I need to block the filler vent somehow to smoke test the system. What if I reconnect the pipes to the filler neck and plug them? I have a P0441 and a P2420 code.

 

sorry, but have never done this on a tundra and each car is a bit different. The vent line does go to that area, as I pulled it and checked it when having issues with filling the tank. just giving some guidelines for testing an evap system. tacomas are pretty much the same and suggesting searching over there. lots of good guidance.

EDIT: P044x codes are leaks detected during the evap test cycle. . However, P2420 is a code indicating one of the valves is not working (either observable elec problem or ECU not seeing expected result of valve actuation). With toyota, everything except the purge valve is contained in the charcoal canister. From my brief research that is either a something inside the canister has failed OR wiring to the canister, which is surprisingly common. tacomaworld has some posts with elec testing to help find it, but will need tundra wiring diagram.

 

You are the best!