Evap Issue

Looking for help here to diagnose an issue. 2003 Tacoma Quad Cab V6 4x4.

When I fill the gas tank the truck won’t start. It’ll crank until I stop, then if I go again it’ll start after maybe 5 seconds then idle rough. I rev it up for maybe 10-15 seconds to maybe 3000 rpm, then all is back to normal. Also, I can smell fuel near the filler neck/ between the cab and the bed. Lastly, the CEL comes on and reads the Evap small leak code. However, when I clear the code, it stays off for maybe 2-3 weeks before coming back on.

I’m thinking it’s the charcoal canister or maybe the purge valve, but wanted to check here before getting into that since it appears they’re buried on top of the gas tank.

 

Check the o ring on gas cap for wear and cracks and hoses to filler neck. Give the purge valve a couple good wacks(they stick sometimes).

 

Yup, forgot to mention that, already replaced the gas cap. I’ll try giving the valve a tap though

 

is there any gas leaking or just the smell?

 

If the purge valve is stuck open it will constantly dump fuel vapour into the intake.

Try plugging it off.

 

No gas leaking as far as I can tell. I park in the same spot and no marks on the ground. It sounds like the purge valve may be the culprit. Would the easiest way to replace be to take the bed off? Then I could replace anything on top of the fuel tank while I’m at it.

 

Build a smoke machine. Or buy one, they are handy for all kinds of leaks. I've found leaky sewer/water lines with them.

 

The purge valve is under the hood. The charcoal canister is under the bed. You say you smell gas between the bed and cab? I'd fallow down the purge line from the canister to the purge valve. I bet you got a breach in that line.

 

Yeah, I can smell it between the bed and cab. I’ll check that line and also give the purge valve a tap since it’s easier to get to. I’m still not convinced that the hose leaking is all of it though. When filling up not starting makes me want to think that the charcoal is getting full of vapor and it takes me trying to start it to clear it out. Is that what the purge valve does is get rid of that vapor that I’m now getting rid of by trying to start?

 

I’ve had bad sending unit seals cause gas smell from that area before. Usually caused by rust on the tank. As for the not wanting to start that can be a million things. May be related or not. Likely is. Smoke machine is your friend in this case.

 

This is a pretty good description of what the valve does.

https://www.samarins.com/glossary/purge-valve.html

 

I would diagnose the problem before removing the bed or dropping the fuel tank. Try add fuel before the fuel light comes on. Full tanks generate less vapor. Going from two gallons in tank at fill up to full tank displaces a lot of vapor and if the valve is stuck open it will seem like the engine is flooded at start up. Try filling up at 3/4 full tank. Purge valve is on cannister above gas tank. If vehicle is not overhead on a lift dropping the spare will give you more room. Tundras have a purge selnoid under the hood, your Tacoma does not. Your tacoma does have a VSV (vacuum switching valve) under the hood but it would not cause the problem you have.

 

As an experiment, try driving it, then shut off, remove gas cap, wait a minute, put gas cap back, then try to restart. See if the pressure or vacuum in the tank is related to the problem or if it's actually related to filling the tank.

The purge valve shouldn't open when starting or idling. If it's stuck open it could cause starting problems.

 

UPDATE! I ordered and replaced the purge valve (under the hood) and refueled from about 1/4 tank. Started right up, which is great and resolved that issue. I'll have to wait and see if my CEL comes back on in the next couple weeks, but I appreciate everyone's advice! Great fix for a few bucks.

 

Good job joe. Does your V6 have the charcoal cannister and purge valve under the hood or did you replace the purge selnoid oem#25860-75160 also known in the aftermarket as VSV or vacuum switching valve ??

 

What CEL did you get? Was it PO0446?

 

P0446 indicates voltage drop in EVAP sensors. OP never mentioned code # but I bet it was P0441 indicated by symptoms presented,

 

That is something Ive no read before. I get that one intermittently. Clear it and it stays away for a while.

 

check the hose going from the the air box to the evap stuff... ive seen them routed wrong and act like that.

 

evap codes and their respective monitors are 2 trip codes with a specific set of test parameters. Fuel tank must be between 1/4 and 3/4 full. IAT (intake air temp) must be within 20 ish degrees of water temp and there must be a minimum of 8 hrs between starts. This has to be done twice... in english this means the truck has to have gas in the tank, sit for 8hrs until it is cool and do this 2 times.