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Q: Car starts very weakly after filling up with gas.

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Recently I hit a curb in avoiding an accident, blowing the right front tire. After changing the tire, I took it in to the Subaru dealership to diagnose any problems, particularly the Check Engine light which had by now illuminated. After a few trips, replacing tires and so out, it was decided that my Engine light was the result of a bad engine fuel pressure solenoid. I had to wait on the part, so I drove it home. The following morning, I filled up, which is the first time I encountered the weak start up. The car seemed to be responding similar to a motorcycle starting cold without being choked. I took it back, and with the solenoid replaced, the light went out, and I drove home, only to find that the light illuminated again on the way home. The next day, they replaced another part in the same system, and now the light is gone. I was assured the weak start was caused by this faulty system, now replaced. However, now filling it up this morning, the issue remains unresolved.

My car has 138966 miles.
My car has an automatic transmission.

A: Hello and thank you for contacting YourMech...

Hello and thank you for contacting YourMechanic. Sometimes the gas cap vent tends to get stuck shut making the fuel system go into a vacuum. Check the gas cap for the seal to ensure that it is sealing. Make sure that you are filling the vehicle up before it hits 1/4 tank of gas. When it gets to about 1/4 tank, the fuel gets sloshed around with the junk and build up in the bottom of the tank. The pump could pick up the build up and clog the filter.

I recommend replacing the gas cap and seal first then rechecking the system. I also recommend replacing the fuel filter if your vehicle has an inline filter. The filter could be causing a restriction on the system preventing the engine from starting. If you are still having fuel issues with your vehicle, I recommend that you seek out help from a technician, like one from YourMechanic, to assist you with diagnosing your car’s starting issue.

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