Smoke Test for EVAP Leak

My 2003 Tacoma recently started throwing a CEL (P0441 & P0456). Initially I replaced the gas cap with a new OEM cap, cleared the CEL and after a couple days its now back. I've done some reading and it seems it can be something as simple as a cracked/dry-rotted hose in the EVAP path or around the canister, to a leak in the fuel tank due to rust.

If I wanted to smoke test the EVAP system, do I just hook the smoke machine up to the green test port near the drivers side fender under the hood and run the smoke? With the car running or off? And do I need to actuate any valves for the smoke to travel through the entire system?

I do notice a faint gas smell from the outside of the vehicle. I dont see any visible leaks around the tank etc. Im assuming these fumes i smell are related to this EVAP code.

Any guidance would be appreciated. Thanks!

 

yes to the green test port.

evap leaks are either found right away or they take hours, there doesnt seem to be a middle ground. Yes to the faint gas smell as the source... sometimes it is so small that you have to catch the light just right to see the wisp of smoke.

 

Do you do the smoke test with the truck running or off?

Just by connecting to the green test port, it will allow smoke to travel through the entire EVAP system? I dont need a scan took to signal any relays to open or anything?

 

Went down the smoke test path, twice. Was inconclusive both times. After I tore into the top of the gas tank after taking with the bed off and I found all rubber gaskets to be deteriorated, especially the large one for the fuel pump. Replaced three rubber gaskets on the tank and leak gone, no more codes.

 

You can do it without the engine running. I tested mine (no leaks, ended up being a MAF and AFR sensor causing my codes) and wrote it up here:

Chasing the P0171 Engine Light

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Yeah, im going to do the smoke test to make sure its not a leaking hose somewhere in the EVAP path. But im guessing I will have to drop the tank and replace it along with any gaskets etc since they do appear to be a bit rusty.

 

as stated above it can be done either way but the prefered method is engine off. If the PCM commands a purge and you are smoke testing it all will get sucked into the engine/charcaol canister and and you will have no smoke in the sysytem.

I do not know if the PCM in your year Tacoma is bi-directional, menaing can you command the purge valve to open from a scan tool... when I get a chance tonight I will check on my 98. If not you might have to pull the vacuum line(s) off and plug them individually and chase it that way... yes, it is a pain in the rear.

 

I couldnt figure out how to get all the emissions valves to open when I did a smoke test. So I removed every valve and joined each line together with fitting like the one in the picture below to keep the system more or less intact. That was the only way I was able to find my leak when doing a smoke test. I didn't have the right computer program/device to manually manipulate the valves from closed to open.

 

It would have to be one hell of a leak to see with the engine running.

Engine is off, seal the air intake by a plastic bag over the air cleaner. Get a $10 party style fog Machine and shoot it into the vacuum line of your master cylinder.