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Ask The NAPA Experts: How To Check Fuel Pressure

Ask The NAPA Experts: How To Check Fuel Pressure

You might know how to check the fuel level, but do you know how to check fuel pressure? There’s a handy gauge on the dashboard that tells you how much fuel is in the gas tank, but if that fuel isn’t reaching the engine under enough pressure, a mechanical failure could be brewing. Let’s take a look at the process necessary to check fuel pressure.

What Does Low Fuel Pressure Mean?fuel pressure gauge

If fuel can’t reach the injector with enough force to atomize the fuel, then the engine won’t run right. More often than not low fuel pressure means a failing fuel pump. A bad fuel pump might limp along for a little while, but eventually it won’t build enough pressure to feed the engine. 

How To Check Fuel Pressure Using A Fuel Pressure Gauge

To check fuel pressure, you will need a fuel pressure gauge (also called a fuel system pressure tester). Make sure you are working in a well-ventilated area, as some fuel fumes may escape during the procedure.

  1. Turn off the engine.
  2. Open the hood.
  3. Locate the fuel rail. You may need to remove the engine cover for access.
  4. Locate the Schrader valve on the fuel rail. This is where the fuel pressure will be tested.
  5. Remove the cap from the fuel rail Schrader valve.
  6. Attach the fuel pressure tester, making sure the connection is tight.
  7. If the fuel pressure tester has a pressure relief hose, route it to a proper container to capture the released fuel. A fuel can makes a perfect catch container, and the fuel can then be used later.
  8. Turn the ignition switch to “on,” but do not start the engine. The fuel pump will pressurize the fuel system, and you will be able to read the fuel pressure gauge.

To test the fuel pressure with the engine running, leave the fuel pressure gauge attached, but place it where it will not contact any of the rotating engine accessories (fan, fan belt, pulleys, etc), and ensure the gauge will not fall due to engine vibration. You may wish to have an assistant hold the fuel pressure gauge. 

  1. Start the engine, and observe the fuel pressure gauge. Refer to a vehicle repair manual for fuel pressure specifications.
  2. Once you have taken the fuel pressure reading, shut off the engine.
  3. With the pressure relief hose secured to a container, release the fuel pressure from the gauge. Properly dispose of the released fuel or reuse it.
  4. Disconnect the fuel pressure gauge from the Schrader valve on the fuel rail.
  5. Wipe up any fuel that has spilled, and dry the spill area thoroughly. 
  6. Place the cap back on the Schrader valve.
  7. Replace the engine cover, if it was removed.
  8. Close the hood.

How To Check Fuel Pressure Using A Diagnostic Tool

Wondering how to check fuel pressure without gauge access? Checking fuel pressure using an OBD diagnostic tool can perform this vehicle test. The exact procedure will vary based on the manufacturer. Refer to the user manual for instructions on how to view live data using the OBD tool. 

In the case of the Actron CP9670, start at the Diagnostic Menu and select the “View Data” option. The tool will scan for available parameter identifications (PID) that can be read. Once the tool has read all the PIDs, it will prompt the user to “Select Data to View.” Choose “Entire Data List” for a readout of all the discovered PIDs. In that list should be a line called “FUEL PRES” or a similar term. That diagnostic reading is the current fuel pressure.

For those who are more tech savvy, there are smartphone apps that can connect directly to a third-party OBD-II wireless transmitter. These apps display the real-time information flowing through the onboard diagnostic system. Information like engine temperature, transmission fluid temperature, fuel pressure and oil pressure are commonly available, but will depend on the app.

Monitoring Fuel Pressure

If you are the kind of driver who prefers to keep a constant eye on what’s going on under the hood, consider installing a fuel pressure gauge. There are a wide variety of gauge styles to match your interior, while also delivering needed information. You can keep an eye on fuel pressure, oil pressure, oil temperature and more with an aftermarket gauge set

If you have a performance vehicle or work vehicle, keeping an eye on engine vitals can help stop a problem before it starts. You can use a mechanical gauge attached directly to the fuel system under the hood, or a digital gauge in the cabin that uses a sending unit.

Frequently Asked Questions:

What Are The Symptoms Of Low Fuel Pressure?

Common low fuel pressure symptoms:

  • Vehicle will not start or keeps stalling
  • Long engine cranking time
  • Hesitation when accelerating
  • Engine is low on power
  • Check engine light is one (engine lean, misfire OBD-II codes stored)

What Are Symptoms Of A Bad Fuel Pressure Regulator?

If the fuel pressure readings are erratic or not within the specification, those may be symptoms of a bad fuel pressure regulator

What Are Symptoms Of A Bad Fuel Pressure Sensor?

If the fuel pressure sensor has gone bad, you may have an illuminated check engine light, trouble getting the engine to start due to low fuel pressure, or reduced engine power. 

If your engine isn’t running right or the check engine light is on, then a fuel pressure check can be a good starting point for diagnosis. As you can see, the process is pretty straightforward with the right diagnostic tool. Your local NAPA Auto Parts store and NAPAonline carry a wide variety of fuel pressure testing tools to fit your needs. 

Don’t feel like leaving the house or don’t have the time? Order on NAPAonline to get One-Day Shipping on 160,000+ products. However you choose to shop, make sure to take advantage of NAPA Rewards to receive 1 Point for every dollar you spend. When you earn 100 Points, you automatically get $5 off your next purchase! 

Don’t feel like testing fuel pressure yourself or just don’t have time? You can also swing by your local NAPA Auto Care for a fuel pressure check. Their ASE Certified technicians have the right tools and training to diagnose any fuel related issues that your car, truck or SUV experience. 

Photo courtesy of Wikimedia Commons.

Brian Medford View All

With an automotive writing career spanning over two decades, Brian has a passion for sharing the automotive lifestyle. An avid DIYer he can usually be found working on one of his many project cars. His current collection includes a 1969 Olds Delta 88 convertible and a slant-6 powered 1975 Plymouth Duster.

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