fuel tank always be full at 90%

Question

For the past couple of months, I've been having trouble filling my gas tank. I have a 2004 civic Honda, which has a 52-liter tank.

When I buy gas, the pump clicks off after dispensing only two or three gallons. Knowing the tank can't possibly be full, I keep working on filling the tank, at a rate of less than a gallon per click, until 10-12 (possibly more) gallons later I see gas come out of the tube. (There's no other way to work out when my tank's full as I have no way of determining how much fuel is in the tank to begin with.)

Initially, I only experienced this issue at one particular gas station. Now, it happens everywhere.

This problem is annoying for two reasons:

It takes a long time to fill my tank, and I risk wasting gas if I overfill the tank. I like to keep track of my mileage, but I can't do so if I don't know how much gas is being used. I don't really want to make gas overflowing be the point from which I measure. What might be going wrong?

Answer 1

I have seen two things cause this problem. The first is an obstruction in the fuel filler neck. This could be caused by damage or a foreign object logged in the neck.

The second is if a EVAP vent solenoid is stuck closed. The evaporative emissions system collects access vapors from the fuel tank in a charcoal canister. To dispose of the collected vapors the car draws air through the canister and burns it through an engine. This is controlled by the purge solenoid. To make sure that the system is working correctly and there aren't any holes or a forgotten gas cap the system has a vent solenoid. To check the system the car will shut the vent solenoid and use the purge solenoid to draw the system into a vacuum. If the system can hold a vacuum then there are no leaks and everything functions correctly. The car is also equipped with on board vapor recovery, a system that traps the vapors that are inside the gas tank as it's being filled with fuel.

If the vent solenoid is stuck closed the vapors inside the tank cannot escape and the fuel filling nozzle at the gas station thinks that the tank is full. The fastest way to check this is to disconnect the hose from the back of the canister or if the solenoid is connected to the canister with a separate hose then disconnect that hose. Then take the car to a gas station and fill it. If the solenoid was bad the car will take gas with no problem. If the canister has multiple hoses the biggest one is the one your looking for.