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Mike V.
Mike V., Subaru Technician
Category: Subaru
Satisfied Customers: 23611
Experience:  Certified Subaru Technician, factory trained by Subaru.
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My subaru imprezza won't let me fill the tank. My Dad says

Customer Question

my subaru imprezza won't let me fill the tank. My Dad says its a vapor lock. What do I do? Its 100 degrees and I need gas.
JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual?
Customer: what
JA: What year is your Impreza?
Customer: 2010
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I am in Oregon, in the wilderness.
JA: Anything else you think the mechanic should know?
Customer: what
Submitted: 2 months ago.
Category: Subaru
Expert:  Mike V. replied 2 months ago.

Hi there,

Is or has the check engine light been on when the car is running?

Customer: replied 2 months ago.
Customer: replied 2 months ago.
I am trying to fill the tank and the gas flies out
Customer: replied 2 months ago.
my dad says its a vapor lock because its 100 degrees outside
Customer: replied 2 months ago.
anybody there?
Expert:  Mike V. replied 2 months ago.


Usually the source of the problem is a bad vent control valve. Basically when you fill the tank the vapors go into the charcoal canister. If the vent control valve doesn't open when it's suppose to, the engine can't pull the fuel vapors out of the canister. There isn't any place for the vapors to go, so the gas comes back and kicks the pump off.

What we have to do is try to get the vapors out of the canister which is mounted inside the car. Do you have any vehicle knowledge so we can try and do this?

Customer: replied 2 months ago.
No. Should I let the car cool off, and try to trickle the gas into the tank?
Customer: replied 2 months ago.
the car was running great until we pulled in to get gas.
Expert:  Mike V. replied 2 months ago.

Yes, but leave the cap off. This should allow some of the fuel vapors to exit the tank and the charcoal canister, the result being the car will take some gas. You will have to add it super slow, but leaving the cap off will let it breath the vapors out.

Once you can, then have it repaired.

After you fill it up, leave the cap loose as well. This should help it pull out the vapors. Since it only happens at certain RPMS, just running it at idle won't really do anything.

The car will run fine with a loose cap, worst case the check engine light will come on.

Please let me know what more I can do to assist you today. Also, please remember to rate my answer, Just Answer does not compensate me for my time and resources. Follow up questions are included in the price of your question. If you are using the free trial, or have a subscription a rating is still required.
Thank you so much!

Expert:  Mike V. replied 2 months ago.

I hadn't heard back from you so I thought I would touch base, do you need further assistance with this?

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