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Won't start EXCLUSIVELY after I fill the tank

Background: My 02 camry (155k) ran great but I noticed grease/oil on the front of the engine so I had a local mechanic take a look. He replaced the front valve cover gasket, timing belt, and while he was in there, the water pump. He made me take it to the dealer to reset/recalibrate the stability control sensor because after disconnecting the battery to perform the work my “VSC”, “trac off” and check engine lights were on. I got it back along with a list of work they thought I needed (replace the rear valve cover gasket, dog bone engine mount, and a bunch of bs I don’t need).

Problem: Quickly my check engine light is back on. I fill up gas and I can’t get it to turn over. The owner of the shop gets it to turn over by gassing it a bunch while turning the key. My mechanic later tells me the check engine light is due to a bum gas cap. He replaces that and the dog bone mount. Next day check engine is back on AND the next time I get gas the same thing happens - it won’t turn over until I gas it, then it turns over and stalls a few times until I really gas it and it turns over and takes. Every other time I try to start the car it turns over first try. Both times I filled up I wasn’t close to running out of gas or anything. I don’t think the gas cap or the fuel injectors went bad coincidentally the same day the dude had his hands in the engine. Thanks in advance for any thoughts you may contribute.

Your car is equipped with a vapor recovery system that absorbs the gasoline vapors in a carbon canister as you re-fuel…A rather complex system of tubing and valves accomplish this. When this system malfunctions, the vapors can pour into the engines air intake during fueling and flood the engine. To clear these fumes, hold the gas pedal on the floor when you re-start the engine…

To fix the problem, the defective part in the system must be located and replaced. As you have discovered, it’s not the gas cap…Think “purge valve”

Thanks for your response. It looks like there is a vapor pressure sensor in that system …maybe it was another sensor that needed to be “reset” following prolonged disconnection of the battery associated with the original work…?

Fill the tank to 3/4 and call it a day.

One thing you could try is to simply remove the gas cap and see if that helps. If so, you’ll know it is some kind of venting problem at least. Venting problems may well be worse when the tank is full, as there is less airspace left over. And if removing the gas cap allows the car to start right up, at least you’ll have a way to start the car after filling it up with gas. Starting or driving the car with the gas cap off might well be dangerous, so talk to your mechanic first before trying this. And carry a big fire extinguisher until you get this fuel problem resolved.

Removing the gas cap will set off an error code in my experience.

Yes it will, but it’s also a good test to see if there’s a venting problem. Error code or not, the car will start if the reason it’s not starting now is because the tank is not venting properly.

Have your EVR system checked. Enhanced vapor recovery

I think the problem may be an onboard refueling vapor recovery valve hanging up. The attached document is from a 2005 Scion tC and should be similar to yours. You may want to ask the dealer parts department for your exact drawing.

http://tijil.org/Scion_Docs/Scion_06_misc_docs/2007sciontc_ncf%20Folder/2azfeemi.pdf