The only way to tell for sure is to remove the filter and blow through it. If there鈥檚 little resistance, the filter is still okay and does not need to be replaced. But if there鈥檚 more than minimal resistance, the filter is dirty and should be replaced.
CAUTION: Gasoline is poisonous, does not taste very good and may burn sensitive lips. So don鈥檛 hold the filter to your mouth to blow through it. Instead, attach a short piece of clean rubber hose to the filter and then blow through the hose to test the filter.
Filter Problems
A completely plugged fuel filter will stop your engine cold by choking off the flow of fuel to the carburetor or injectors. The engine may not start, or it may start, then stall and die.
Some filters have a spring-loaded bypass, however, that allows fuel to bypass the filter element if it becomes clogged. Fuel continues to flow, but it may carry dirt to the carburetor or injectors, which can create additional problems.
A partially restricted filter will usually pass enough fuel to keep the engine running at idle or low speed, but may starve the engine for fuel at higher speeds or loads. So your engine may run fine putting around town, but sputter and lack power when you try to drive at highway speeds or pass someone.
Tank Filter
Located inside the fuel tank is a screen or mesh sock that acts like a prefilter to keep big pieces of dirt and rust from being drawn into the fuel pickup tube or tank-mounted electric fuel pump. If the screen becomes clogged with debris, it can have the same effect as a plugged or dirty fuel filter. Therefore, if you鈥檝e been experiencing a fuel starvation problem and have replaced the fuel filter -- and it didn鈥檛 help -- the screen in the tank is probably the culprit. To clean or replace it, the fuel tank usually has to be removed.
