Trouble Starting After Fill-Up

Some background: My car (06 speed6) has had some troubles starting after filling up with gas recently. It used to just idle funky for ~5-10 seconds then settle to its normal idle and drive fine afterwards. Recently it got to the point that my car would not start without giving the gas pedal a little flutter while I turned the key.

I tried only filling up to a half tank the last time I went to the gas station and the car started just fine. That means that (I think) it only happens when the car gets filled up all the way. Also, it doesn't ever have any issues starting everyday, just filling up.

I did do some research on this subject and found that it happens with more than just Mazdaspeeds, or Mazdas in general. Some people say it's the purge valve, some say its the charcoal canister. From my research most people that replaced the purge valve still had the same issue... which leads me to believe the charcoal canister is the issue. I couldn't find any record of someone replacing the charcoal canister/emissions system so I do not know if that would fix the problem. Sounds like an expensive fix for a not so bad problem.

Anyways, I am not too well versed in emissions systems for cars so I thought I would reach out and see if anyone has had a similar issue or if anyone has any comments on my theory. I am going to go do more research on the emissions system to see if I can figure it out.

Also want to note that I have run a 25% blend of e85 in the past and never overfill the gas tank by clicking the pump a few more times after it stops pumping.

 

It's likely, especially if you tend to only run the car for fairly short distances (say city driving for 10-15 min. at a time), that the evap canister isn't having enough time to purge properly. As a result, the evap system, and the purge valve in particular, doesn't have a chance to operate properly.

That said, I've had this exact behavior happen a number of times, and the answer has always been to replace the purge valve.

 

+1 on this. 100% purge valve! Had this problem twice on my Juan and once on my MS6. Cheap easy fix.

 

I'll definitely try this fix. Has anyone tried the non-oem Dorman part? It's a lot cheaper than OEM. Here's the part: http://www.autozone.com/1/products/77679-canister-purge-valve-911-702-dorman-911-702.html

Also, for future people reading this thread can we break down exactly why the purge valve is the issue? I did some research on EVAP systems and how they work so I'll give it a shot but no guarantees I have it right.

Let's first start by breaking down a basic EVAP control system. Older cars had a more simple system of getting fuel vapors out of the gas tank and into the atmosphere when filling the tank up and while gas is being taken from the tank (usually done by a vented gas cap). This is needed because the fuel tank is an enclosed space that needs air to fill up the voids when gas leaves and air to leave when gas is put in the tank. Most newer systems have the air that is displaced run into a charcoal canister where the fuel vapors are stored then released into the intake manifold while driving. This eliminates fuel vapors from entering the atmosphere which makes the EPA happy. The purge valve is placed in-between the charcoal canister and intake manifold. The valve is controlled electrically allowing the vapors to be sent into the intake manifold at proper times. This is important because the fuel vapors (air) is technically un-metered air entering the engine which makes the car hard to start after filling up (making air exit the fuel tank).

Please let me know if this is a good explanation!

 

I ended up purchasing the Dorman part. I installed it today and went to fill up. Happy to report that there were no issues. Hopefully this part lasts for a while.

 

Happy to have helped.