Do Gas Pumps Shut Off While You’re Filling Up? Check For Clogs | Phoenix Auto
SYNOPSIS: When it comes to maintaining your vehicle's performance, the gas tank is a critical component that should never be overlooked. At Phoenix Auto Repair, we understand the importance of its function.
Do Gas Pumps Shut Off While You’re Filling Up?
BY: Daniel Langham, Phoenix Auto Repair
You’re at the gas pump, filling up your tank, but the pump keeps shutting off before you even reach half a tank. A few different factors can cause this issue, but it’s usually an easy fix. Let’s dive into it.
If you're experiencing this problem and there is no check engine light on, we’ll start with some basic steps. If you do have a check engine light, we’ll address that later.
First, remove the gas cap and take a look at the filler neck. Use a flashlight to inspect for any obstructions. There may be a flap that you will need to push out of the way to see more clearly. If your car does not have that flap, then congratulations, you are in good shape! If you have a borescope, slide the camera down into the filler neck for a better look at what is going on inside.
We can start by checking the screen at the top, and it looks clear, which is a positive sign. You might find a check ball at the top, which is normal. However, watch out, because there is a possibility that the check ball could be stuck.
Next, you'll want to inspect the filler neck from underneath the vehicle. You can visually inspect it from the outside if you don't have a borescope. Look for any kinks or twists, especially if you recently had a fuel pump replaced; sometimes, when the tank is reinstalled, it can get routed improperly.
As you check, make sure that the area where the filler neck meets the gas tank is unobstructed and smooth. If that area looks good and you don't see any kinks, then there should be no problem filling the fuel in the tank. The problem likely lies within the venting system.
When adding fuel, the air needs to escape somewhere, typically through an EVAP canister and an EVAP vent valve. It's essential to check these components. The EVAP charcoal canister is located nearby, and as the fuel tank fills, air moves through a tube into the canister. This air contains vapor that the charcoal absorbs, preventing it from being released into the atmosphere before it exits through the vent.
The major culprit of clogging up the EVAP canister is overfilling the tank. When you fill-up your tank, the pump will shut off at a certain point, and that is where you should stop. If you keep topping off the tank, that extra fuel has got to go somewhere, and it can go down the vapor line and wind up filling the canister with fuel, causing a clogged canister!
If you disconnect these lines and fuel leaks out, you'll know that this is where your issue is coming from. People often top off their fuel tanks, which they shouldn't do. You'll need to clean out the lines and replace the canister. There's another vacuum line that goes to the front of the truck, and this is a line that connects to the valve.
Now, let's look at the clogged evaporative (EVAP) canister. When you first pull the canister out, tip it over to see if any gasoline comes out of the holes. If there's no gasoline, and you can hear that there's a blockage inside, it means it is clogged. To confirm this, you can use a balloon. Cover this vent on the outside and put a little compressed air in it. The balloon won't inflate much at first, but when you remove it, there will be pressure inside. You can see the canister actually swell up, indicating that it’s completely clogged.
When you look at a new, unclogged canister with our balloon test, you’ll see the balloon pumps up, and when you remove it, it comes right out. You will be able to feel air coming out. If you shake it, you won't hear any noise. In contrast, when you shake the old one, you can hear it's broken up inside.
Now, with a bad canister, some of the internal components could have broken up and entered the valve. If the canister is found to be faulty, it’s a good idea to replace the valve. If the canister ends up being good, your next step would be to check the valve. If your evaporative vent valve is stuck closed, that could trigger a check engine light, which may direct you toward inspecting the valve anyway.
A solenoid valve that’s controlled by power is normally open all the time. When the computer needs to close the valve, it sends power to it. Inside, there’s a little filter that prevents moisture from entering the valve. This filter is designed to be positioned high to avoid any water ingress. However, if there is dust in this area clogging the little screen, it won’t function properly.
Sometimes, you might actually find a spider nesting in the area, which could be causing your issue. In that case, you just need to clean out the spider nest, and you should be good to go. So, definitely check for spiders or other critters that have lost their way!
You can also use compressed air to blow out any debris in both directions. There are usually no blockages present, but keep in mind that the valve itself could be failing due to debris, which might intermittently cause this issue. That’s something to look out for.
Installing a new evaporative canister vent valve is possible, and made even easier with help from professional mechanics like ours here at Phoenix Auto Repair. These valves are very common for either causing a plugged condition or becoming stuck open, which leads to a different type of check engine light (but is still an EVAP concern.)
It's important to avoid topping off your fuel tank when filling up at the gas station. Overfilling can lead to several serious issues, including damaging your fuel system and causing fuel to spill out, which is not only wasteful but also harmful to the environment. Excess fuel may enter the vapor recovery system, potentially causing it to malfunction. To ensure your vehicle runs efficiently and to promote safety, always stop filling your tank when the nozzle automatically clicks off. This not only protects your car but also contributes to a cleaner environment.
