Where is the bleed screw on the fuel filter?

The bleed screw on a fuel filter is typically located at the top or side of the filter housing. This screw allows air to be bled from the fuel system, which is an important step when servicing or replacing a fuel filter.

Understanding the Fuel Filter and Bleed Screw

The fuel filter is a critical component in a vehicle's fuel system, responsible for removing contaminants and impurities from the fuel before it reaches the engine. The bleed screw, also known as the air bleed screw, is a small, threaded bolt or plug that is used to release any air that may have entered the fuel system.

When air gets trapped in the fuel system, it can cause issues with the fuel pump, injectors, and engine performance. Bleeding the system by opening the bleed screw allows this air to be released, ensuring a smooth and consistent flow of fuel to the engine.

Locating the Bleed Screw

The bleed screw is typically located at the top or side of the fuel filter housing. It may be a small, slotted or hex-headed bolt that can be turned with a screwdriver or wrench. The location of the bleed screw can vary depending on the make, model, and year of the vehicle, so it's important to consult the vehicle's service manual or repair information to determine the exact location.

Bleeding the Fuel System

• Locate the fuel filter and identify the bleed screw.


• Place a rag or container under the bleed screw to catch any fuel that may drip out.


• Slowly turn the bleed screw counterclockwise, allowing air to escape from the system.


• Continue turning the screw until fuel begins to drip out, indicating that the air has been bled from the system.


• Tighten the bleed screw back up, being careful not to overtighten it.

Properly bleeding the fuel system is an important step when servicing or replacing a fuel filter, as it ensures the fuel system is free of air and operating at optimal efficiency.

How to bleed a diesel fuel filter?

To bleed a diesel fuel filter, locate the bleed screw or pump handle on the filter housing, and use it to push fuel and air out until only solid, bubble-free fuel comes out. For most systems, turn the ignition to the "on" position to activate the fuel pump (if applicable) and pump the primer several times, or turn the key multiple times for self-bleeding systems, while keeping any bleed screws or connections slightly loose. Once clear fuel flows, tighten the bleed screw and start the engine. 
This video demonstrates how to bleed air out using the primer pump: 1mBenjamin SahlstromYouTube · Aug 30, 2018
Steps to bleed a diesel fuel filter 
This video shows how to bleed a diesel fuel system after a filter change: 59sFast RustYouTube · Mar 7, 2020

1. Prepare the system: Turn the ignition to the "on" or "auxiliary" position to activate any electric fuel pumps. If there is no electric pump, you will use the hand primer pump on the filter housing. 
2. Open the bleed screw/valve: Loosen the bleed screw or valve on top of the fuel filter, typically by a half to one full turn, to allow air and fuel to escape. 
3. Pump or cycle the system:
   • If using a hand pump: Pump it several times, or until the lever is firm, to push the air out. 
   • If there's an electric pump: Cycle the ignition key to the "on" position several times, or let it crank the engine, if the system is self-bleeding. For a non-self-bleeding system, this may also activate a pump to help push fuel through. 
4. Watch for bubbles: Watch the open bleed screw. Keep pumping or cycling the ignition until a steady stream of fuel, free of any air bubbles, comes out. 
5. Close the bleed screw: Once only clear fuel is flowing, tighten the bleed screw securely to prevent air from getting back into the system. 
6. Start the engine: After bleeding, try to start the engine. It may take some cranking, especially if air is still trapped in the high-pressure lines. 
7. Bleed injection lines (if necessary): If the engine still runs poorly or doesn't start, you may need to bleed air from the injection lines. To do this, crack the fuel line connection at the injector, crank the engine until you see solid fuel, and then tighten the connection. Repeat for each injector, and be careful of fuel spills. 

This video shows how to bleed air out from the injector lines: 59sCanadian RedneckYouTube · Dec 17, 2015
Additional tips

• Always clean the area around the filter housing before starting to prevent dirt from entering the fuel system. 
• If the hand primer pump handle does not have full travel, you may need to turn the engine's crankshaft a quarter turn to reposition the cam that operates the pump. 
• Be aware that some modern systems are self-bleeding and may only require cycling the ignition key a few times without starting. 
• Never loosen the connections at the injectors on common rail diesel systems, as these operate under extremely high pressure and can be dangerous. 

This video explains how to de-pressurize a fuel line: 54sSave Money TVYouTube · Aug 16, 2024

Where is the bleed screw on a fuel filter?

Your fuel system should have some bleed screws installed in some key locations. The primary fuel filter has one on top of the housing and there's one on the fuel line connector at the injector timing pump. Unscrew the bleed screw on the top of the primary fuel filter a half turn.

How to get air out of a fuel filter?

To get air out of a fuel filter, you will need to bleed the system by loosening a bleeder screw, and then use a priming pump or by cycling the ignition to force fuel and air out until a solid stream of fuel without bubbles is visible. Once the air is purged, tighten the screw and check if the engine starts and runs smoothly.
 
Method 1: Using a primer pump or lever
This video shows how to bleed a diesel fuel system using a primer pump: 55sBenjamin SahlstromYouTube · Aug 30, 2018

1. Loosen the bleeder screw: Find the bleeder screw, usually on top of the fuel filter housing, and use a wrench to loosen it about a half to a full turn counter-clockwise. 
2. Prime the system: Use the manual primer pump lever located on the fuel pump to pump several times. You should see air bubbles and fuel begin to flow from the bleeder screw. 
3. Continue until fuel flows steadily: Keep pumping until only a consistent stream of fuel, with no air bubbles, comes out. 
4. Tighten the screw: While still pumping, tighten the bleeder screw to prevent air from re-entering. Tighten it snugly once the air is completely purged. 

Method 2: Using the ignition (for systems with an electric fuel pump) 
You can watch this video to learn how to bleed air out of a fuel filter using the ignition system: 55sSolis Tractors USAYouTube · Feb 25, 2025

1. Cycle the key: Turn the ignition key to the "on" position (without starting the engine) for about 10-20 seconds. You should hear the electric fuel pump run. 
2. Repeat a few times: Repeat this process two or three times. This will help fill the filter and push air through the lines. 
3. Crank the engine: After cycling the key, attempt to start the engine. It may take a few tries, but it should start as the air is purged. 

Method 3: Bleeding at the injectors (if the engine still runs poorly) 
This video demonstrates how to bleed the fuel system by releasing pressure from the fuel rail: 54sSave Money TVYouTube · Aug 16, 2024

1. Loosen the injector line: With the engine off, use a wrench to loosen the banjo bolt fitting at the base of one of the fuel injection lines where it connects to the injector. 
2. Crank the engine: Crank the engine. It will likely start and run rough, spitting out air and fuel. 
3. Tighten and repeat: As soon as a steady stream of fuel without bubbles comes out, tighten the fitting. Repeat this process for each injector line until the engine runs smoothly. 

How to bleed the air out of the fuel system?

To depressurize a fuel system, first, locate and remove the fuel pump fuse or relay, then start the engine to run until it stalls, which will use the remaining fuel. Alternatively, for a system with a Schrader valve on the fuel rail, place a rag around the valve, press the center stem with a tool to release the pressure, and have a rag ready to catch any drips. 
Method 1: Remove the fuel pump fuse or relay 
This video demonstrates how to depressurize a fuel system by removing the fuel pump relay: 38sMark's GarageYouTube · Aug 6, 2013

1. Disconnect the negative battery terminal: to prevent electrical shorts. 
2. Locate the fuse or relay box: under the dashboard or in the engine compartment. 
3. Find the fuel pump relay: by checking the diagram on the fuse box lid. 
4. Remove the fuel pump relay: and reinstall the negative battery terminal. 
5. Start the engine: and let it run until it stalls, which indicates the fuel system has released its pressure. 
6. Reinstall the relay: after the work is complete to ensure the car can restart. 

Method 2: Use the Schrader valve 
This video shows how to use the Schrader valve to release fuel pressure: 46sSave Money TVYouTube · Aug 16, 2024

1. Wear eye protection: and ensure the engine is cool. 
2. Locate the Schrader valve: on the fuel rail, which looks like a tire valve stem. 
3. Place a rag around the valve: to catch any spray. 
4. Use a small flathead screwdriver: or similar tool to press the central valve stem, releasing the fuel pressure slowly. 
5. Ensure the valve is facing away from you: to avoid being sprayed.