Rough idle or difficult to start? Your fuel filter may need replacing. Fortunately, changing your fuel filter may be an inexpensive way of sorting these issues out. Here in the UK, the standard of fuel is very good with low amounts of contaminants leading to a long life for our fuel filters. But, that doesn’t mean your fuel filter will last indefinitely, they are eventually prone to wear and clogging. In this article, we will cover what exactly a fuel filter does and the major symptoms that would indicate a replacement is due.
What Is A Fuel Filter?
The primary purpose of a fuel filter is to stop contaminants such as debris, dirt or rust from reaching the engine. If a fuel filter is clogged or working ineffectively this can cause several problems. Some diesel filters will have a drain at the bottom to allow you to discard any water contamination.
Most modern fuel filters will be in the form of a changeable metal cartridge containing durable pleated paper for restricting contamination. In most cases, the entire unit is replaced but some will have a sealable lid for replacing the filter itself.
What Are The Symptoms Of A Bad Fuel Filter?
Difficult to Start
Is your car taking a few extra turns to get started? This could be a sign of a clogged filter restricting fuel to the engine. These extra turns will cause an additional drain on the battery, especially during the winter months.
For most vehicles, the idle speed is between 600 and 1000 RPM. If your vehicle has an idle speed constantly dipping below normal, it may indicate a fuel filter change is needed as fuel flow has been restricted.
A rough idle occurs when the delicate mixture of fuel and air is incorrect. The rev counter will be rising and falling as the engine struggles to maintain a steady rate of rotation. You may notice it does not sound as smooth as a properly functioning engine. These symptoms would include misfires and splutter at idle or while driving.
When a fuel filter is seriously clogged it may restrict the fuel so much it stalls just after ignition or when out on the road. At this stage, the fuel filter will need replacing soon to avoid further inconvenience.
Low MPG and Poor Performance
Your ECU and fuel pump overcompensate with more fuel when the filter is clogged. This incorrect mix of fuel can severely hinder performance making the vehicle sluggish on acceleration and have trouble maintaining a consistent speed. The excess fuel will make your engine run rich and reduce MPG.
Some vehicles will have a fuel pressure sensor that will illuminate a yellow warning light on your dashboard. This may be an engine management light or a specific fuel filter light. (check the warning lights page in your handbook if you are unsure of the symbol)
Fuel Pump Failure
Any of the symptoms above could also be signs of a failing fuel pump. The fuel pump is designed to move a consistent stream of fuel from the tank to the engine. If this stream is disrupted the engine will not function correctly. Most modern fuel pumps are electronically driven and contain many moving parts that will eventually succumb to wear. An inspection will be required to determine if this is the cause.
When Does My Fuel Filter Need Replacing?
Fuel filters are notoriously hardy components but they will need replacing eventually. Older and classic vehicles will need filter replacement more frequently from every 2 years and 20,000 miles. The intervals on modern fuel filters vary widely between makes and models with changes expected between 30,000 and 100,000 miles. This is often undertaken as part of your routine service schedule. However, you can find out your vehicle’s recommended intervals by checking the handbook or calling a garage. Likewise, if you have experienced any of the symptoms listed above it may indicate your fuel filter is due for a timely replacement.
How To Replace The Fuel Filter
This is not a simple task and shouldn’t be undertaken unless you have good technical experience and in some cases specialist tools. The fuel filter is often difficult to access and will require techniques such as bleeding and releasing fuel pressure. A local mechanic or service centre will be happy to undertake this routine maintenance and get your vehicle running as it should once more.
We hope this article about replacing your fuel filter will start you on the journey of diagnosing the problem. Please share this article within your social media channels if you have found it useful. If you have had your own specific problems with your fuel filter, then please comment below or ask for help in our forum.