Automotive fuel filters come in a variety of designs and are located in different locations. While some fuel filters are made to avoid installing them backwards, some can be installed backwards and may or may not create problems.
Symptoms: what happens if I put the fuel filter upside down
An upside down fuel filter can restrict or stop fuel flow to the engine. If, after changing a fuel filter, the engine suddenly shows a loss of performance, the filter should be inspected to see if it is installed correctly.
Other problems: what happens if I put the fuel filter upside down
Worse than performance issues, a fuel filter that was installed backwards can cause problems that produce no noticeable symptoms. A backwards fuel filter can restrict fuel from entering the engine, but the restriction is compensated by the fuel pump. This will result in increased fuel pump wear and may cause pump failure. While fuel filters are inexpensive and easy to change, fuel pumps are expensive and difficult to change.
Correct installation: correct position of the fuel filter
Fuel filters that can be installed backwards have printing or symbols on the filter to indicate how the filter should be installed. If there is any concern that a filter has been installed backwards, the filter should be removed and inspected to ensure proper installation.