Fuel Rail Pressure Sensor Guide for Diesel Engines

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The fuel rail pressure sensor on a diesel engine is an electronic sensor that monitors fuel rail pressure. The fuel rail is a metal tube that connects the fuel delivery system to the engine. If this sensor goes bad, you’ll likely experience problems starting the engine, poor engine performance, and a check engine light.

Your diesel engine’s fuel delivery system relies on several parts working in unison to deliver the right amount of fuel on demand. The fuel rail pressure sensor helps the powertrain control module deliver the correct fuel to the engine. What happens if this part goes bad? Can you keep driving your truck?

ProSource Diesel takes a look at the fuel rail pressure sensor, what it does, the symptoms of a bad one, and what it takes to replace it.

What is a Fuel Rail Pressure Sensor?

The fuel rail pressure sensor is sometimes called a fuel pressure sensor or a high-pressure sensor. Its function is to monitor the pressure inside the fuel rail, which is a metal tube that connects the engine to the fuel delivery system.

The sensor consists of an electric circuit and a semiconductor. As fuel passes through the rail, the sensor measures the pressure and sends a signal to the PCM (powertrain control module).

Which Diesel Trucks Have a Fuel Rail Pressure Sensor?

Most Powerstroke, Duramax, and Cummins diesel engines have a fuel rail pressure sensor. The location of the sensor might be different depending on the engine. For example, on a 2016 Chevy truck with the L5P Duramax engine, the sensor is located on the passenger side fuel rail beneath the EGR cooler.

Where is the Fuel Rail Pressure Sensor Located?

As mentioned above, the fuel rail pressure sensor location might be different depending on your engine layout. However, in general, it is mounted on the fuel rail, which is a metal pipe that connects the fuel system to the engine. It should be on the other end of the pipe from the pressure control valve.

What Happens if the Fuel Rail Pressure Sensor Goes Bad?

If your fuel rail pressure sensor goes bad, you probably won’t be able to get your engine started and have it remain running. If it does start and remain running, it will likely run rich or lean, which can cause further problems with your engine in the future.

In other words, if you have to keep your engine going in an emergency, it’s likely safe to do so for a short time. However, you need to replace the bad sensor as soon as possible.

What are the Symptoms of a Bad Fuel Rail Pressure Sensor?

Most fuel rail pressure sensors last as long as the engine they’re installed in. However, any part can potentially fail earlier than expected. The good news is that your sensor probably won’t fail suddenly, some symptoms indicate its impending failure.

An illuminated check engine light could be your first warning. If the ECM (engine control module, also called an ECU) detects unusual sensor input, it will trigger the check engine light. A failing fuel pressure sensor will disrupt the fuel supply, which keeps the engine from getting the correct amount of fuel.

Problems starting your engine is another possible symptom as well as poor engine performance. The ECM has to deliver the correct amount of pressure in the fuel rail to allow for proper engine performance.

If the ECM gets faulty readings from the fuel rail pressure sensor, it can’t accurately deliver the right amount of pressure. Since the wrong amount of fuel will cause your engine to run rich or lean, you’re likely to experience decreased fuel economy when the fuel rail pressure sensor is going bad.

Too much or not enough fuel can also cause your engine to misfire or run rough.

How to Test Fuel Rail Pressure Sensor with Multimeter

If you want to check whether your fuel rail pressure sensor is going bad or if it might be something else, you can use a multimeter to confirm it. Let’s take a look at the steps.

1) Locate your fuel rail pressure sensor on the fuel rail.

2) Disconnect the electrical connector.

3) Set your multimeter on Ohms.

4) Attach the multimeter probes to the sensor terminals. If there’s no continuity, then you can confirm that the sensor is indeed bad and should be replaced.

5) If there is continuity, you can reconnect the electrical connector and start the engine to confirm proper operation.

How to Bypass a Fuel Rail Pressure Sensor

Technically, you could unplug the fuel rail pressure sensor if it’s bad and run without it. However, you’ll get reduced power and throttle due to the pump running at a set speed. This will reduce your fuel economy and cause extra emissions. It’s better to simply replace the sensor.

How to Reset Fuel Rail Pressure Sensor

If you have high or low pressure upon replacing the sensor, then you may need to clear the fault with a scanner tool. Disconnecting the battery and reconnecting it can also help in resetting it.

How To Replace a Fuel Rail Pressure Sensor

If you need to replace your fuel rail pressure sensor, you’ll first need to locate it, remove everything that’s in the way and then disconnect it.

There should be two connections; the electrical connectors and then a retaining clip or bolts.

Remove the old sensor and connect a new sensor in its place. Reconnect the wiring and secure the retaining clip or bolts and then replace all the parts you had to take off.

If you disconnected the battery before replacing the sensor, reconnect that and then start your engine to ensure proper operation.

We recommend finding a how-to video specific to your diesel engine because the location and access to the fuel rail pressure sensor can vary wildly.

Rely on ProSource Diesel for quality diesel truck parts like a fuel rail pressure sensor. You can find performance upgrades and OEM replacement parts for Cummins, Duramax, and Powerstroke engines in our catalog.

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