How Autozone Can Help Check Fuel Pressure

AutoZone offers a fuel pressure test kit for purchase or rental, which can be used to check fuel pressure. The kit includes a test gauge, hoses, adapters, and a multimeter, among other items. It is designed to be used by one person and can be connected to the fuel system of most vehicles. AutoZone also provides fuel injectors and other tools for troubleshooting fuel pump relay issues.

AutoZone's fuel pressure test kit

AutoZone offers a range of fuel pressure test kits, which can be used to check the fuel pump and fuel system of your car. The test kits can be purchased or rented, with free shipping and in-store or curbside pick-up options available.

The OEMTOOLS Fuel Pressure Test Kit comes with a limited-lifetime warranty and is compact for portability. It uses SAE-certified quick connects and can be used to diagnose common fuel system problems such as a failing fuel pump, faulty pressure, or blocked filters.

The Innova Fuel Injection Pressure Tester helps identify and diagnose low fuel pressure, a faulty fuel pressure regulator, leaking injectors, fuel leaks, and clogged fuel filters. It includes adapters for Ford, GM, Chrysler, and a "tee" adapter for import vehicles. It also features a durable 16" hose with solid brass fittings and an easy-to-read 2 1/2" dial face with a 0-100 PSI scale.

AutoZone also offers the Mityvac Fuel Pressure Tester Kit and ACTRON Ford Fuel Adapter for Fuel Pressure Tester Kit CP7818.

Using a fuel pressure test kit from AutoZone requires your vehicle to have a Schrader valve test port, which is available on most domestic fuel-injected vehicles and many imported cars. If your car doesn't have the right valve, an adapter can be used.

How to use a fuel pressure tester

A fuel pressure tester is used to test whether your car's fuel pump is working and whether enough fuel pressure is getting to the injectors. Here is a step-by-step guide on how to use a fuel pressure tester:

Step 1: Check for gas in the tank

This may sound obvious, but it's important to check that there is actually gas in the tank. Don't trust the fuel gauge, as it could be faulty. Add at least two gallons to the tank and try another start. If the car starts, check the fuel gauge for internal failure and replace it if necessary. If the new gauge shows the same high fuel level, the issue is a failed fuel sending unit in the gas tank.

Step 2: Verify that the fuel pump works

Head back to the fuel tank and ask an assistant to turn the ignition switch to "On". Listen for a two-second whir, hum, or series of rapid clicks as the fuel pump pressurizes the fuel line to the engine. No noise could mean that the pump is not getting power or has failed. Check the fuel pump fuse and relay. If both are good, check the wiring to the pump. If voltage is present when turned on, then the pump has failed.

Step 3: Connect the fuel pressure tester

Pop the hood and find a Schrader valve fitting on the fuel rail. Remove the Schrader valve cap and attach the appropriate fuel pressure tester fitting. Make sure it threads on properly for a leak-proof fit.

Step 4: Check the psi reading

Turn the ignition to "on", not start, and check the psi reading. Wait and watch for a psi drop, which indicates a leak in the system. If the pressure remains the same after 5-10 minutes, the system is holding pressure well. If the fuel pressure drops over this time, there is a leak in the fuel system.

Step 5: Start the engine

Start the engine and let it idle. You should see steady fuel pressure, within a few psi of the recommended pressure. Once warmed up, slowly rev the engine, making sure the pressure rises with the RPMs. If your fuel pressure holds steady, rises with engine speed, and is at the recommended pressure, then your engine problem does not seem fuel-related.

Step 6: Understand your fuel pressure readings

If you have zero fuel pressure, this means the pump is dead or not getting power. Check the fuel pump fuse and then verify power to the pump with a multimeter. If it's good, swap out the fuel pump.

Low fuel pressure could mean that the fuel filter is clogged or the pump is failing. If it is a serviceable type filter, change the fuel filter. This could also be improper tank venting, an emissions issue caused by a loose gas cap. Check that the cap gasket isn't damaged and tighten it until it clicks.

High fuel pressure could be caused by a clogged or kinked fuel return line, a bad fuel pump driver module, or a powertrain control module. These would likely store a code and show a "check engine" light. High fuel pressure can also be caused by a faulty fuel pressure regulator.

How to connect a fuel pressure tester

To connect a fuel pressure tester, safety should be the top priority. Fuel vapours are highly flammable, so the process should be carried out in a well-ventilated area with a fire extinguisher nearby. Wear safety goggles and gloves for protection.

With a cold engine, open the hood and locate the Schrader valve fitting on the fuel rail. This may be hidden under a fuel rail cover or another plastic engine cover. Once found, remove the Schrader valve cap and attach the appropriate fuel pressure tester fitting. Ensure that it threads on properly for a leak-proof fit.

Turn the ignition to "on", but not "start". Observe the psi reading and wait for any drops in pressure, which would indicate a leak in the system. If the pressure remains the same after 5-10 minutes, the system is holding pressure well. If the pressure drops by 20 psi, for example, this indicates a leak in the fuel system.

After this, start the engine and let it idle. The fuel pressure should be steady and within a few psi of the recommended pressure. Once the engine is warmed up, slowly rev the engine and check that the pressure rises with the RPMs. If the pressure holds steady and rises with engine speed, the engine problem is likely not fuel-related.

Understanding fuel pressure readings

Zero Fuel Pressure:

If the fuel pressure gauge reads zero, it indicates that the fuel pump is not functioning. In such cases, start by checking the fuel pump fuse. Verify if the pump is receiving power using a multimeter, and if it's receiving power but still not working, it's likely faulty and needs to be replaced.

Low Fuel Pressure:

Low fuel pressure can cause various issues, including slow startup, low performance, misfires, and stalling. This issue could be due to a clogged fuel filter or a failing fuel pump. Start by checking if the fuel filter is serviceable and consider replacing it if necessary. Improper tank venting or a loose gas cap could also contribute to low fuel pressure. Ensure the gas cap gasket is intact and tightened securely.

High Fuel Pressure:

High fuel pressure can lead to excessive fuel consumption, black smoke from unburned fuel, catalytic converter overheating, and rough idling. Potential causes of high fuel pressure include a clogged or kinked fuel return line, a faulty fuel pump driver module, or a faulty powertrain control module. Additionally, a faulty fuel pressure regulator could be the culprit.

Understanding Effective Pressure:

It's important to distinguish between rail pressure and effective pressure (or differential pressure). Rail pressure refers to the pressure inside the rail, which can be measured using a fuel pressure sensor attached to the rail. Effective pressure, on the other hand, is the actual applied pressure across the injector. It is the pressure differential between the rail pressure and the manifold pressure. Understanding effective pressure is crucial for properly setting up the fuel system and ensuring accurate injector flow rates.

Fuel Pressure Tester:

To measure fuel pressure, you can use a fuel pressure tester, which typically consists of a gauge attached to a fuel hose with multiple fittings. This allows you to connect to the fuel system of most vehicles. When connected and pressurised, the tester displays the pressure in psi, allowing you to compare it to the recommended pressure for your specific engine.

Signs of low fuel pressure

AutoZone does offer a fuel pressure test kit, which can be used to diagnose common fuel system problems such as a failing fuel pump, faulty pressure, or blocked filters.

Low fuel pressure can cause a range of issues with your vehicle, including:

• Hesitation while accelerating
• Rough idle or stalling
• Engine light blinking, indicating a random misfire
• Shaking or vibrating of the engine
• Lack of acceleration
• Stalling problems

If you are experiencing any of these issues, it is recommended to have a professional mechanic complete a check-up of your vehicle to identify and resolve the problem.

Frequently asked questions