Signs of a Bad Fuel Filter：
As fuel flows through the filter, the pleated material filters out any contaminants on its way to the engine. These contaminants could be dirt, salts, or any moisture or debris that got kicked into the giant tank when the fuel was received at the gas station. When the fuel filter is filled with these things, it restricts the flow of fuel to the engine. Eventually, symptoms are sure to appear.
Power Loss Under Load
Restricting the fuel supply to the engine may allow the engine to maintain the proper fuel pressure at idle. However, when you accelerate or pull a load, the demand for fuel is much greater. A clogged fuel filter prevents the fuel rail from staying full of fuel, limiting the power the engine can produce.
Check Engine Light On
If the injectors are not receiving enough pressurized fuel, there may not be enough fuel to spray into the cylinders for combustion. There may be a "P0171 System Too Lean" code stored in the powertrain control module, triggering the check engine light.
Engine Misrunning or Stalling
With an insufficient fuel supply, the engine may misfire or stall while driving or idling. It's like pinching the straw when you try to drink soda through it. When you close the straw, you can't keep the energy-generating fluid flowing.
Your engine won't start
When you turn the key, the fuel pump pressurizes the fuel going into the fuel supply line. A clogged fuel filter may prevent the fuel from pressurizing the section between the filter and the engine. Your engine may not start due to lack of fuel, or it may start for a second and then stall again.
Fuel Pump Stalls
Excessive demand for fuel puts pressure on the fuel pump. The fuel pump is constantly running at peak performance, trying to force fuel into the restricted supply line. This can cause the fuel pump relay to activate, a fuse to blow, or the fuel pump to stop operating altogether.
Decreased fuel economy
It may seem counterintuitive, but a clogged fuel filter actually causes higher fuel consumption. The PCM thinks the air-fuel mixture is lean, and to compensate, it commands more fuel to mix with the air being sucked into the engine to get the power you want in your car. While it's not performing very well, you're burning more fuel than you would if the fuel was flowing in the correct amount.
