Replacing Fuel Injection Pressure Sensors: A Step-By-Step Guide

A fuel rail pressure sensor is an important component that helps to reduce evaporative emissions by allowing the engine just enough fuel to run correctly. When this sensor begins to malfunction, there can be difficulty starting the engine, and the engine may operate erratically or even cut out. This article will provide a step-by-step guide on how to replace a fuel injection pressure sensor, including the tools required and safety precautions to take.

Characteristics and Values Table for Replacing a Fuel Injection Pressure Sensor

Disconnect the fuel supply

Disconnecting the fuel supply is an important first step when replacing a fuel injection pressure sensor. This is because the sensor is typically located on the injector pump or fuel rail, so you need to relieve the pressure from the fuel system before removing the sensor. Here is a step-by-step guide on how to do this:

Step 1: Park Your Vehicle

Park your vehicle on a flat, hard surface and ensure that the transmission is in park for automatics or in first gear for manuals. This is an important safety precaution and will make it easier to work on your vehicle.

Step 2: Disconnect the Fuel Supply

There are typically two ways to disconnect the fuel supply:

• Removing the fuel pump fuse: This method may work for some vehicles, but it depends on the specific model.
• Disconnecting the fuel pump cutoff switch: The cutoff switch is usually located inside the vehicle, either on the driver's side near the brake and accelerator pedals or on the passenger side behind the kick panel.

Step 3: Remove Pressure from the Fuel System

Once you have disconnected the fuel supply, you need to remove the remaining pressure from the fuel system. To do this, crank the engine over. It will sputter and stall as it uses up any remaining pressurized fuel. Turn the ignition off after it stalls.

Step 4: Gain Access to the Sensor

The fuel injection pressure sensor may be obstructed by components such as the air filter box or air duct. Carefully remove any items that are blocking access to the sensor.

Step 5: Prepare for Fuel Leakage

Place a rag or two under and around the sensor because, even though you have removed the pressure, some fuel may still leak out when you remove the sensor.

At this point, you have successfully disconnected the fuel supply and relieved the pressure from the fuel system. You can now proceed to remove and replace the fuel injection pressure sensor. Remember to exercise extreme caution when working with fuel, and ensure that you are working in a well-ventilated area.

Remove pressure from the fuel system

To relieve the pressure from the fuel system, you must first park your vehicle on a flat, hard surface. Ensure that the transmission is in park for automatics or in first gear for manuals.

Next, locate the negative battery cable and disconnect it using a wrench. This will prevent sparks, which could ignite fuel and fuel vapors.

Now, you can relieve the pressure using one of the following methods:

Relieving Pressure with the Fuel Pressure Regulator:

• Locate the fuel pressure regulator on the fuel rail, which is mounted along the top area of the engine.
• Remove the vacuum hose from the top of the fuel pressure regulator by hand.
• Connect a hand-operated vacuum pump to the top of the pressure regulator.
• Apply approximately 16 inches of mercury (Hg) of vacuum to the regulator to push the fuel in the lines back into the fuel tank.

Relieving Pressure with the Fuel Pump Connector:

• Access the sending unit/fuel pump assembly, which is usually located on top of the fuel tank.
• If your vehicle has an access door to the fuel tank, open it by removing the rear seat or trim in the trunk. If not, you may need to raise the rear of your vehicle using a floor jack and support it on jack stands to access the assembly.
• Unplug the fuel pump electrical connector on the sending unit/pump assembly.
• Start the engine and let it idle until it stalls. Then, turn off the ignition switch.

Relieving Pressure with the Fuel Pump Fuse and Relay:

• Locate the fuel pump fuse, typically under the dashboard or in the engine compartment, usually on the driver's side. Refer to your owner's manual if needed.
• Remove the fuse with your hand or a pair of pliers, or remove the fuel pump relay.
• Start the engine and let it idle until it stalls.
• Disconnect the negative battery cable.

Relieving Pressure with the Ford Inertia Switch (for Ford models):

• Locate the inertia switch, which is typically found around the trunk, rear compartment, or under the dashboard.
• Unplug the inertia switch's electrical connector.
• Start the engine and let it run until it stalls.
• Disconnect the negative battery cable.

Relieving Pressure with the Test-Port Valve:

• Disconnect the negative battery cable.
• Locate the Schrader valve on the fuel rail around the top of the engine. It looks like a bicycle tire valve.
• Unscrew the valve cap if there is one.
• Cover the port valve with a shop rag to catch any fuel spray.
• Push the valve in using a small screwdriver until fuel stops flowing through the valve.
• Replace the test-port valve cap.

Remember to always loosen or remove the fuel filler cap when working on the fuel tank to relieve pressure build-up. Additionally, always disconnect the negative battery cable when working on the fuel system.

Access the fuel rail pressure sensor

Accessing the fuel rail pressure sensor can be a challenging task, especially if your vehicle has a small engine bay. Here is a detailed guide to help you access and replace the fuel rail pressure sensor:

Locate the Sensor

The fuel rail pressure sensor is typically located somewhere on the engine's fuel rail, which is responsible for distributing fuel to the fuel injectors. It can be tucked in on the side or right on top. The fuel rail is a metal tube that connects the fuel delivery system to the engine.

Prepare for Access

Before attempting to access the sensor, it is crucial to ensure your safety and the stability of your vehicle. Park your car on a flat, hard surface, and make sure the transmission is in park for automatics or in first gear for manuals. It is also recommended to install a nine-volt battery saver into your cigarette lighter to keep your computer live and retain your vehicle's settings.

Accessing the Sensor

Now, you can open the vehicle's hood and disconnect the battery. Remove the ground cable from the battery's negative post to disable the power to the ignition and fuel system. If your engine has an intake that overlaps or obstructs the fuel rail sensor, you will need to remove it before proceeding.

Relieve Pressure

Locate the Schrader valve or test port on the fuel rail. Put on safety glasses and protective clothing. Place a small drip pan under the rail, cover the port with a towel, and use a small flat screwdriver to open the valve. This will release the pressure in the fuel rail. If there is no Schrader valve or test port, you will need to remove the supply fuel hose to the fuel rail using a drip pan and a fuel hose quick-disconnect tool.

Disconnect the Sensor

Remove the harness and mounting hardware from the fuel rail sensor. At this point, you should be able to take the fuel rail sensor off the fuel rail. Clean the area with a lint-free cloth, and use an electrical cleaner to remove any debris from the fuel rail sensor harness.

Install the New Sensor

Install the new fuel rail sensor onto the fuel rail, screwing in the mounting hardware finger-tight, and then tightening it with an inch-pound torque wrench. Secure the sensor by tightening the mounting hardware further. Plug in the fuel rail sensor harness to the sensor, and reinstall any brackets or components that were previously removed.

Post-Installation Checks

After installing the new sensor, there are a few critical steps to ensure everything is functioning correctly. Reconnect the ground cable to the battery's negative post, and tighten the battery clamp securely. Check for any leaks using a combustible gas detector, and cycle the ignition key on and off a few times to ensure the entire fuel rail is full and pressurized. Finally, test drive your vehicle, listening for any unusual engine sounds or vibrations and monitoring the fuel level and dashboard for any warning lights.

Remove and replace the sensor

To remove and replace the fuel injection pressure sensor, follow these steps:

Park your vehicle on a flat, hard surface and ensure that the transmission is in park for automatics or in first gear for manuals. It is important to take safety precautions, as fuel is combustible. Be sure to work on the vehicle in a well-ventilated area.

Install a nine-volt battery saver into your cigarette lighter to keep your computer live and retain your vehicle's settings. If you do not have one, that is okay, but you will have to reset all the settings in your vehicle later. Disconnect your battery by removing the ground cable from the battery's negative post, disabling the power to the ignition and fuel system.

Open the vehicle's hood and remove the engine cover if there is one. Remove any brackets or components that may be obstructing access to the fuel rail sensor. If your engine has an intake that overlaps or is transverse-mounted to the fuel rail sensor, you must remove the intake before proceeding.

Locate the Schrader valve or test port on the fuel rail. Put on safety glasses and protective clothing. Place a small drip pan under the rail and cover the port with a towel. Use a small flat-tip screwdriver to open the valve and release the pressure in the fuel rail. If there is no test port or Schrader valve, you will need to remove the supply fuel hose to the fuel rail using a drip pan and a fuel hose quick disconnect tool.

Remove the harness and mounting hardware from the fuel rail sensor. Take the sensor off the fuel rail. Clean the fuel rail with a lint-free cloth, and clean the sensor harness with an electrical cleaner to remove any debris.

Now, you are ready to install the new fuel rail sensor. Place the new sensor onto the fuel rail and screw in the mounting hardware finger-tight. Tighten the mounting hardware to 12 inch-pounds, then give it a final turn of 1/8. This will secure the sensor in place. Plug in the sensor harness and reinstall any brackets or components that you had to remove to access the sensor.

If you had to remove the pressure fuel line to the fuel rail, be sure to reconnect it now. Install the engine cover by snapping it back into place.

Finally, you can reconnect the ground cable to the battery's negative post and remove the nine-volt battery saver (if used). Tighten the battery clamp and ensure a good connection. Turn the ignition key on and off 3 to 4 times to pressurize the fuel rail. Check for any leaks using a combustible gas detector and sniff for any fuel odours.

Once you have confirmed there are no leaks, you can start the vehicle and test drive it. During the test drive, listen for any engine cylinders not firing correctly and feel for any vibrations. Monitor the dashboard for the fuel level and for any warning lights. If the check engine light comes on, further diagnosis of the fuel system or an electrical issue may be required.

Check for leaks

Checking for Leaks

After replacing the fuel rail sensor, you must check for leaks to prevent safety risks and loss of engine power.

First, reconnect the ground cable to the battery's negative post and tighten the battery clamp. Ensure the connection is good.

Cycle the ignition key to the "on" position 3 to 4 times. This will ensure the entire fuel rail is full of fuel and pressurised.

Next, use a combustible gas detector to check all the connections for leaks. Sniff the air for any fuel odours.

If you do not have a combustible gas detector, you can use a shop light and your sense of smell to check for leaks. Hold the shop light over the fuel injection rail and look very closely at each fuel injector head where it connects to the fuel rail. Look for any obvious dribbling leaks or fuel spray patterns on the rail, injector body, or cylinder head. A leak at the injector head indicates bad O-ring seals inside the injector body.

If you suspect a leak, you can perform a fuel pressure leak-down test. Install a fuel pressure gauge on the fuel pressure test fitting on the rail. If your fuel rail does not have a pressure test fitting, use a T fitting between the fuel line and the injector inlet location and attach the pressure gauge hose to the middle of the T fitting.

Cycle the ignition key to the "on" position several times and look at the reading on the gauge. Refer to your owner's manual for the correct psi for a residual pressure test. Depending on the vehicle, the reading will be anywhere from 30 to 80 psi. The pressure should hold for several minutes without dropping. Any pressure drop below specifications indicates one or more leaking injectors.

Preventing Leaks

To prevent leakage, fuel pumps should be tested for leaks during component production and final assembly. Maximum allowable leak rates typically range from 5*10-4 to 5*10-5 mbar l/s.

Frequently asked questions