Using Autozone's Fuel Pump Pressure Kit Tester: A Guide

If your car is running rougher or using gas less efficiently, it may be time for a fuel pressure test. AutoZone makes checking fuel pressure easier than ever. Get a fuel pressure test kit and check the fuel pump and fuel system on your ride today. The requirement for using an AutoZone fuel pressure gauge with your vehicle, having a Schrader valve test port, means it works on most domestic fuel-injected vehicles and many imported cars. If your car doesn’t have the right valve, an adapter can help you out. If you suspect that the pressure in your fuel line may be off, come to AutoZone. They have everything you need to make sure your fuel injector is working right.

How to test fuel pressure

Testing fuel pressure can help diagnose drivability issues with your vehicle. Most vehicles have two fuel lines: a pressure line and a return line. You will need to test the pressure line.

Firstly, determine which line is your pressure line by referring to the vehicle manufacturer's service manual. Next, bleed the pressure from the system. To do this, remove the fuel pump relay from the power distribution box, then crank the vehicle. This will drain the pressure without the fuel pump.

Now, open up the system and install a pressure gauge. You may need to use a rag to catch any fuel that drips out of the line. Once the pressure gauge is installed, start the vehicle and check the fuel pressure. With the vehicle running, time the release for about 15 seconds, then release the valve and measure the fuel pressure.

If the pressure drops off very quickly, you may experience a hard start issue. If the pressure holds for about 15 minutes, your check valve and pressure regulator are likely functioning properly.

Finally, you can start the vehicle and allow the pressure to bleed off so you can remove the fuel pressure test gauge. Do this slowly, as there may still be some residual pressure in the system.

Understanding Fuel Pressure Readings

Zero fuel pressure means the pump is dead or not getting power. Check the fuel pump fuse and verify power to the pump with a multimeter. If the pump has power, swap it out.

Low fuel pressure could be caused by a clogged fuel filter or a failing pump. Change the fuel filter, or if it is a serviceable type filter, clean it. Low fuel pressure could also be caused by improper tank venting or a loose gas cap.

High fuel pressure will cause excessive fuel consumption, black smoke, an overheating catalytic converter, and rough idle. Suspects for high fuel pressure include a clogged or kinked fuel return line, a bad fuel pump driver module or powertrain control module, or a faulty fuel pressure regulator.

How to connect a fuel pressure tester

To connect a fuel pressure tester, it is important to take the necessary safety precautions. Fuel vapors are highly flammable, so the process should be carried out in a well-ventilated area, and a fire extinguisher should be kept nearby. It is also recommended to wear safety glasses and gloves.

With that out of the way, you can begin by popping the hood of your entirely cold engine. Find a Schrader valve fitting on the fuel rail. These are common on most vehicles, but they may be hidden under a fuel rail cover or another plastic engine cover. Once you've located the Schrader valve, remove its cap. Attach the appropriate fuel pressure tester fitting, ensuring that it threads on properly for a leak-proof fit.

Turn the ignition to the "on" position, but not to start. Check the psi reading and wait to see if there is a drop in pressure, which would indicate a leak in the system. If the pressure remains steady, the system is holding pressure well.

If you suspect a leak, you can leave the tester connected for 5-10 minutes. If the fuel pressure drops over that time, there is likely a leak in the fuel system. Check for drips underneath the vehicle to help narrow down the location of the leak. Keep in mind that it could also be leaking internally from a faulty fuel injector.

After checking for leaks, start your engine and let it idle. The fuel pressure should remain steady, within a few psi of the recommended pressure for your specific engine. Once the engine has warmed up, slowly rev it and observe whether the pressure rises with the RPMs.

If your fuel pressure holds steady, rises with engine speed, and is within the recommended range, then your engine problem is likely not fuel-related.

Understanding fuel pressure readings

Fuel pressure readings can help diagnose issues with your car. If your car is not starting, it could be due to a problem with the battery, fuel, fuel pump, or insufficient fuel pressure reaching the injectors. A fuel pressure tester can help you identify the issue.

Zero fuel pressure indicates that the pump is dead or not receiving power. Check the fuel pump fuse and verify power to the pump with a multimeter. If power is being received, the fuel pump needs to be replaced.

Low fuel pressure can cause a slow startup, low performance, misfires, and stalling. This could be due to a clogged fuel filter or a failing pump. If it is a serviceable type filter, replace it. Low fuel pressure can also be caused by improper tank venting or a loose gas cap. Ensure the cap gasket is not damaged and tighten it securely.

High fuel pressure will result in excessive fuel consumption, black smoke from unburned gas, an overheating catalytic converter, and rough idling. Potential causes include a clogged or kinked fuel return line, a faulty fuel pump driver module or powertrain control module, or a faulty fuel pressure regulator. These issues may trigger a "check engine" light and store a code.

It is important to refer to your vehicle's repair or service manual for specific fuel pressure requirements and diagnostic procedures. Different engines have varying fuel pressure needs, and deviations from the manufacturer's specifications can help identify the source of the problem.

How to check fuel pressure

Checking your fuel pressure is one of the first steps in diagnosing drivability issues with your vehicle. Here is a step-by-step guide on how to check your fuel pressure using an AutoZone fuel pump pressure kit tester:

Step 1: Identify the Pressure Line

Most vehicles today have two fuel lines going to the engine: a pressure line and a return line. You will need to determine which line is the pressure line. Refer to the vehicle manufacturer's service manual to safely attach a pressure gauge.

Step 2: Bleed the Pressure from the System

Locate the power distribution box and remove the fuel pump relay to drain the pressure from the system. You can crank the vehicle, and you will hear it attempt to start with low pressure.

Step 3: Install the Pressure Gauge

Once the pressure has been drained, open up the system and install the pressure gauge. Remove the safety clip and use a rag to catch any fuel that may drip from the line. Install the retainer and make sure it is seated properly by listening for an audible click.

Step 4: Start the Vehicle and Measure Fuel Pressure

Start the vehicle and let it run for about 15 seconds. Release the valve and then measure your fuel pressure. Shut off the vehicle and check the residual pressure. If the pressure drops off quickly, you may experience a hard start issue. Monitor the residual pressure for about 15 minutes. If the pressure holds, your check valve and pressure regulator are functioning properly.

Step 5: Remove the Pressure Gauge

After testing, slowly remove the pressure gauge, as there may still be some residual pressure in the system. Use a rag to catch any fuel that may drip from the line.

Step 6: Interpret the Fuel Pressure Readings

Now that you have measured your fuel pressure, you can refer to your vehicle's repair manual to determine if the pressure is within the recommended range. Zero fuel pressure indicates a dead pump or a lack of power. Low fuel pressure could be due to a clogged fuel filter or a failing pump. High fuel pressure could be caused by a clogged or kinked fuel return line, a faulty fuel pump driver module, or a powertrain control module.

What to do before buying a tester

Before you purchase a fuel pressure tester, there are a few things you should do to troubleshoot your vehicle's fuel system.

Firstly, check that there is gas in the tank. Even if the fuel gauge shows a full tank, it could be faulty, so add at least two gallons of gas and try to start the engine. If it starts, the issue may be with the fuel gauge or the fuel sending unit in the gas tank.

The next step is to verify that the fuel pump is working. Ask an assistant to turn the ignition switch to "On" and listen for a two-second whir, hum, or series of rapid clicks as the fuel pump pressurizes the fuel line. If there is no noise, this could be due to a lack of power or a failed pump. Check the fuel pump fuse and relay, and if these are functioning, check the wiring to the pump.

If the pump is delivering fuel, you can then break out the fuel pressure tester. It is important to perform these steps in a well-ventilated area with a fire extinguisher nearby, as fuel vapors are highly flammable.

To use the tester, locate the Schrader valve fitting on the fuel rail and remove the valve cap. Attach the fuel pressure tester fitting, ensuring it is leakproof. Turn the ignition to "On" and check the psi reading, waiting to see if there is a drop in pressure, which could indicate a leak in the system.

If you are still experiencing issues, it may be time to purchase a fuel pressure tester to help diagnose the problem.

Frequently asked questions