How to Unstop a Car Gas Tank Vent

by James Roberts
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A blocked vent pipe to the car's gas tank can be a real problem. Most people are not even aware such a problem can occur or what it might lead to. A car's fuel tank is much more than a tank with a fuel hose leading to it. Modern vehicles have a vent hose that is part of the fuel system. When this line is clogged or blocked, fueling repercussions follow. The most prevalent of these is the auto shutoff problem. Attempts to fuel the vehicle fail, because the back pressure constantly shuts off the pump.

Step 1

Extend a compressor line into the air vent line, and give it a shot of air. If the line is not blocked, there will be a gurgling sound as air is forced into the tank. Lack of such a sound may indicate a blockage, and a further check is required.

Step 2

Disconnect the canister vent line to the gas tank, and try blowing through it. This is a short line, so it should be obvious if there is a blockage. If it seems it might be clogged, use compressed air to thoroughly blow out the line. A can of compressed air, like the air cans used to blow around computer keyboards, will often do the trick -- if a long piece of plastic tubing can be engineered instead of the short stick-hose they typically have. Blowing through the line will verify whether there is a blockage and often will unblock the line.

Step 3

Push a length of small-gauge plastic tubing or large heavy wire through the vent pipe, to check for a physical blockage. This is often the case if wasps have gotten into the vent line and built a nest.

Step 4

Drain the tank, and allow the interior to dry out. Reconnect the fuel line and the vent hose, and retry the compressed air blow. There should be no blockage at this point. Attempt to refill the tank see if the problem has gone away.

Step 5

The remaining problem possibilities are valve-related and cannot be cleared by hand. Replace the canister assembly, the canister close valve and vent valve. This is typically done by an auto mechanic or car-handy friend.

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