Where is the secondary fuel filter located?

The exact location of a vehicle’s secondary fuel filter varies by make, model, and year. In many modern diesel engines and some gasoline systems, the secondary filter is either in the engine bay, along the frame rail under the vehicle, or inside the fuel pump module in the tank. Always consult your owner’s manual or a service manual for your specific model to be sure.

What the secondary fuel filter does and why it matters

A secondary fuel filter works in conjunction with the primary filter to remove contaminants that could harm fuel injectors, pumps, or the engine. It is part of a two-stage filtration system found on many diesel engines and a few gasoline applications. Keeping it properly located, accessible, and maintained helps prevent fuel delivery issues, reduced performance, and potential damage from water or sediment in the fuel supply.

Common locations for the secondary fuel filter

Different vehicles place the secondary filter in different spots. The following locations are among the most frequently seen in modern vehicles:

• Engine bay, often mounted on the side or near the firewall, sometimes as a separate canister alongside the primary filter.


• Along the frame rail under the vehicle, typically near the fuel lines or near the fuel filter housing for easy servicing from the underside.


• Inside the fuel tank as part of the fuel pump module (an in-tank design) in some newer or specialized diesel and gasoline systems.


• Integrated with the fuel filter module in some manufacturers’ modular filter assemblies, which may combine primary and secondary filtration in a single unit.

There is no universal placement that applies to every model. The exact arrangement depends on the vehicle family, market specifications, and engineering design choices made by the manufacturer.

How to locate the secondary fuel filter on your specific model

To identify the precise location on your vehicle, follow these practical steps:

1. Check the owner’s manual or the official service manual for your exact make, model, and year; search for terms like “fuel filter,” “secondary filter,” or “water separator.”


2. Inspect the engine bay for a cylindrical canister with hoses connected to it near the engine or firewall; this is a common engine-side location for the secondary filter.


3. Look underneath the vehicle along the frame rails or near the fuel lines; many dual-filter setups route lines to a filter mounted there for under-vehicle servicing.


4. If you have an in-tank filter system, locate the fuel pump module in the tank area (often accessed via a rear seat or trunk area on some vehicles) and check the service manual for its filter components.

These steps will help you confirm the exact spot and avoid confusing the secondary filter with the primary fuel filter, water separator, or other fuel-system components.

Safety and maintenance tips

Always depressurize the fuel system before servicing, work in a well-ventilated area, and use proper protective gear. If you’re unsure about the location or how to replace the filter, consult a qualified technician or your dealership service department.

Summary

The location of the secondary fuel filter is not standardized and depends on the vehicle. It can be in the engine bay, along the frame under the vehicle, or inside the fuel tank module. For accurate placement, refer to your owner’s manual or a service manual for your specific model, and use the steps above to locate it safely.

How often should I replace my secondary fuel filter?

For Secondary filters we recommend you replace the cartridge every 40,000kms, or every second time you change your factory filter, whichever comes first. The exception to the above rule would be if you encountered contaminated fuel, in which case you should change the filters early.

Where is the secondary fuel filter?

The secondary fuel filter is typically located in the engine bay, close to the fuel injectors, to ensure the fuel is as clean as possible before entering the high-pressure system. In some vehicles, its position is near the engine oil filter. 
This video shows the location of the secondary fuel filter in the engine bay: 59sA Long Long Way to GOYouTube · Feb 10, 2024

• Location: The secondary filter is almost always inside the engine compartment. 
• Function: It's placed after the primary filter to catch finer particles, as it's the last line of defense before the fuel injectors. 
• Specific placement examples:
  • It may be found under the hood next to the engine oil filter. 
  • In some models, it is located on top of the engine, as seen in this YouTube video. 

Which fuel filter is primary and secondary?

A primary fuel filter removes large contaminants like dirt and rust, typically located between the fuel tank and the engine. A secondary fuel filter is a final line of defense that removes much finer particles after the primary filter, usually positioned closer to the engine to protect the highly sensitive injectors and pumps. Both filters are essential for engine health; the primary handles the big debris and the secondary provides protection from smaller particles. 
This video demonstrates the process of changing both primary and secondary fuel filters: 49sMotor Boat & YachtingYouTube · Jul 16, 2012
Primary fuel filter

• Location: Between the fuel tank and the fuel pump. 
• Purpose: Acts as the first line of defense to remove large particles, such as dirt, rust, and sediment, from the fuel. 
• Efficiency: Captures larger particles, with a typical efficiency of 10–30 microns. 
• Maintenance: Often includes a water separator that can be drained during service intervals. 

Secondary fuel filter

• Location: After the primary filter, typically near the engine, before the fuel enters the injectors. 
• Purpose: Catches any finer particles that may have passed through the primary filter. 
• Efficiency: Removes much smaller particles, often rated at 2–5 microns, which is crucial for protecting sensitive, high-pressure fuel system components. 
• Maintenance: Provides the final layer of protection to prevent damage to components like the fuel pump and injectors. 

You can watch this video to learn about a myth regarding secondary fuel filters and restrictions: 58sDiesel CareYouTube · Sep 14, 2018

Where is the secondary fuel pump located?

All vehicles with fuel injection have a primary fuel pump that's typically located in the fuel tank. Modern vehicles with gasoline direct injection (GDI) also have a second pump, which is a high-pressure pump. This second fuel pump is near the fuel rail in the engine compartment.