Katerina Swanson
If your car is struggling to accelerate, especially on the highway, or you notice other signs that your car might not be getting enough gas, the problem could be caused by a partially blocked or clogged fuel line, fuel filter, pump, or injector. In most cases, a failing fuel pump will cause your vehicle to no longer run, leaving you stranded. However, sometimes your fuel pump will begin to show some subtle signs of failure before it completely breaks down. Knowing these signs and how to test your fuel pump can help you avoid a costly breakdown or a dangerous situation.
Where to go to check the fuel system of a car
| Characteristics | Values |
|---|---|
| At home | Check the fuel pump fuse, listen for a hum from the fuel pump, use a fuel pressure tester, or test for bad fuel. |
| Auto shops | Mechanics can check your fuel system for you. |
| Dealership | Technicians can perform a check at your home or office. |
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What You'll Learn
Check the fuel pump
The fuel pump is a crucial component of a car's fuel system, transferring fuel from the tank to the engine. When something goes wrong with the fuel pump, it can cause significant issues with the car's performance and, in some cases, even leave you stranded. While fuel pump problems can be challenging to diagnose, performing some simple tests can help identify potential issues. Here's a detailed guide on checking the fuel pump:
Locate the Fuel Pump:
The first step is to locate the fuel pump, which is usually found inside the fuel tank. Many vehicles provide access to the pump through an access panel in the trunk or inside the car. However, some vehicles may require lowering the fuel tank to access the pump.
Listen for the Pump's Buzzing or Humming:
With the car turned off and securely parked on a level surface, remove the fuel cap. Have an assistant turn the key to the "on" or "run" position without starting the engine. Listen closely near the tank opening. A properly functioning fuel pump will emit a buzzing or humming sound for a few seconds.
Sometimes, the issue may not be with the pump itself but with the power supplying it. Refer to your owner's manual to locate the fuse box. Identify the fuse associated with the fuel pump and inspect it for signs of failure, such as a blown, broken, or burned fuse. If the fuse appears damaged, replace it and try starting the vehicle again.
Check Voltage at the Pump:
Even if the circuit appears functional, it's important to ensure that voltage is reaching the pump. Consult your vehicle's service manual to determine the proper procedure for checking voltage. Test for source voltage to confirm that the charge is reaching the pump as expected.
Use a Fuel Pressure Gauge:
Investing in a fuel pressure gauge can be helpful for troubleshooting fuel pump issues. These gauges are commonly available at auto parts stores and can be borrowed from machine shops or auto shops. Locate the fuel pump test point, usually near the fuel injectors, and attach the pressure gauge to the test fitting. Have an assistant rev the engine while you monitor the gauge for any abnormalities.
Test the Pump with a Battery:
You can also test the fuel pump with a battery by checking for +12 volts between the top of fuse 32. This test bypasses the standard process and provides a direct voltage supply to the pump. If the pump runs, you should hear it even from inside the car.
Common Signs of Fuel Pump Issues:
It's important to be aware of common signs that your fuel pump may be failing. These can include difficulty in accelerating, especially at higher speeds, struggling to go past a certain speed (e.g., 40 mph), and the car not starting at all. Additionally, keeping up with regular maintenance, such as replacing the fuel filter and ensuring the vehicle is not consistently run low on fuel, can help prevent fuel pump issues.
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Check for bad fuel
If you suspect that your car has bad fuel, there are a few ways to check. Firstly, if your car is struggling to accelerate, particularly on the highway, or you notice other signs that your car is not getting enough gas, this could be due to a partially blocked or clogged fuel line, fuel filter, pump, or injector. A failing fuel pump can cause a great number of issues, and testing it can help solve problems in your car before they become more serious.
A loose gas cap that isn't sealing properly is a key physical sign that your car has bad fuel. This exposes your tank to the elements, making it easier for debris and water to enter your car's fuel system and contaminate the gasoline. If you suspect this is the case, drain the fuel and fill up with a known good gas.
If your car's ignition is hesitant or sputtering, leading to engine misfires and noises, this could be due to bad fuel. As gasoline goes bad, it combusts improperly, resulting in these issues. If this is a problem you notice, change the type of gasoline you are using, check the seal of your car's gas tank, and bring your car to a mechanic if the problem persists.
You can also test the fuel yourself. One method involves placing the gasoline in a graduated cylinder, adding some windshield washer fluid, corking the sample, and shaking the tube. Once the contents have settled, compare how much gasoline you put in to how much is left. This will show you how much alcohol is in the fuel—it should be no more than 10%. Another test involves retrieving a sample of the gasoline to test its volatility, known as Reid Vapor Pressure. Chill the sample and the testing tool on ice for 30 minutes, then pour the fuel into the tool and close it. Place the tool into hot water for 10 minutes and measure the water temperature, then read the pressure from the gauge on the tool. Finally, compare the pressure and temperature to a table that comes with the tool.
If you are unsure of what type of fuel system your car has, or are uncomfortable testing your fuel pump, you should enlist the assistance of a certified mechanic to check your fuel system.
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Test the fuel pressure
Testing the fuel pressure is an important step in checking your car's fuel system. Here is a step-by-step guide on how to do it:
Park your car and engage the parking brake. It is important to ensure your car is securely parked on a level surface for safety reasons. Turn off the engine and allow it to cool down. This ensures your working area is safe.
Locate the fuel pressure test port. The test port is usually located near the fuel injectors, where the pump hooks up with the filter injector rail. Consult your car's manual to find the exact location, as it may vary depending on the vehicle's make and model.
Once you have located the test port, place a rag underneath it to catch any fuel that may be released during the testing process. Then, install the pressure tester to the test port. You can purchase or rent a fuel pressure tester from most auto parts stores, or even borrow one from machine shops or auto shops.
After installing the pressure tester, start the engine and record the pressure reading. You may need an assistant to help with revving the engine while you monitor the gauge.
Different engines have different fuel pressure requirements. For example, older throttle-body injected systems may need as little as 10 psi, while multi-port injection can go up to 60 psi. Check your car's repair manual to find out the specific pressure requirements for your engine.
If the fuel pump is not meeting the required pressure specifications, it may be failing to deliver fuel to the engine. This can cause issues such as slow start-up, low performance, misfires, and stalling.
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Check the fuel filter
The fuel filter is an integral part of the fuel supply system in your vehicle. Its purpose is to clean the fuel in your car before it reaches the engine. An unclogged filter prevents contaminants like dust, dirt, and rust from entering the combustion and fuel chambers by removing these particles.
Most auto mechanics recommend changing the fuel filter every 24 months or 30,000 miles, depending on which comes first. However, various factors can influence how often a fuel filter should be changed, such as the make and model of the car, filter quality, vehicle age, and driving habits. For example, the lifespan of a fuel filter tends to vary according to the make and model of a car. Petrol filters take longer than diesel filters to get clogged, so the replacement time differs.
If you are unsure about how to check your fuel filter, refer to your car's service manual or contact a professional. If you decide to check it yourself, locate the fuel filter first. For most cars, the fuel filter is mounted on the vehicle's frame near the engine. Once you've found the fuel filter, remove any mounting hardware or clamps attached to the fuel lines or fuel filter.
A clogged fuel filter generally causes low fuel pressure, which results in a reduction in engine performance. This is often more noticeable when accelerating, particularly up a steep incline. If your car won't start at all, there are a few quick tests you can run to figure out whether or not it's causing your problems. You can know whether your fuel filter needs replacement simply by doing a straightforward blow test on the device. The tube indicating the flow direction of fuel into the filter is usually labeled. This is an essential part of knowing how to check and change a fuel filter if it’s necessary, as the inlet part of the filter is the part you should blow into. If the fuel filter is unclogged, it should be relatively easy to blow into the filter without much difficulty.
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Check the fuel injectors
It is important to regularly check your car's fuel injectors for any issues, as a failing fuel injector can cause serious problems for your vehicle. Fuel injectors in cars typically last between 50,000 and 100,000 miles, but they will eventually wear out and need to be replaced. Here is a step-by-step guide on how to check your fuel injectors:
Step 1: Pop the Hood
Start by popping the hood of your car while the engine is running. Be extremely careful when leaning into the engine bay, and always keep your eyes open to prevent any accidents or injuries. If you have long hair, be sure to tie it back to prevent it from getting caught in any moving parts.
Step 2: Listen for Clicking
Place a thin metal rod or screwdriver on one of the injectors and lean in close to listen for an audible clicking sound. This clicking indicates that the fuel injector is functioning properly. Repeat this process for each injector in your vehicle. If you find an injector that is not clicking, there may be an issue with that specific injector or the electronic control unit transmitting to the injector.
Step 3: Check for Errors
If your vehicle is equipped with an OBDII scanner and the check engine light is on, use the scanner to check for any errors in the vehicle's computer related to the cylinder or injector. Replacing the faulty injector may solve the problem, but you may also need to have a professional mechanic diagnose your vehicle's electronic control unit and fuel system.
Step 4: Test Flow Rate
To test the flow rate of the injector, set up a pump with a known pressure, such as 50 psi. Then, use a pulse tool calibrated to pulse the injector at a known rate, such as 100 Hz. Place a measuring device, such as a flask with graduations of known value, under the injector. If you notice drips or a poor flow rate, the injector pintle is not sealing properly.
Step 5: Observe Atomization
While the injector is pulsing, pay attention to the pattern and atomization of the fuel. The more atomized the fuel is, the better it will mix with the air and ignite evenly. A low flow rate can cause the engine to run hotter and leaner, leading to potential damage.
Step 6: Test with a Voltage Meter
With the engine running at idle, use a test light to probe the opposite wire of the constants identified in the previous test. Press the sharp end of the probe firmly through the rubber coating until it makes contact with the metal wire inside. Be careful not to push the probe all the way through. Look for a flashing or flickering light. As your helper applies throttle by pressing the gas pedal, the light should flicker more brightly. If the test light fails to light up, the injector may be faulty or there could be an issue with the electronic control unit.
When to Seek Professional Help:
If you are unsure about the condition of your fuel injectors or feel uncomfortable performing these tests, it is best to seek the assistance of a certified mechanic. They can help diagnose and resolve any issues with your fuel system, ensuring the safety and optimal performance of your vehicle.
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Frequently asked questions
You can check your fuel system at home if you have the right tools and some mechanical knowledge. However, if you are unsure about your fuel system or uncomfortable testing it, you should seek the assistance of a certified mechanic.
You can use a fuel pressure tester, a voltage meter, or a fuel test kit to check your fuel system. You can purchase or rent these tools from auto shops or online.
First, hook the pressure gauge to the fuel pump test fitting. Then, have an assistant rev the engine while you check the gauge. If the fuel pressure drops over 10 minutes, there is likely a leak in the fuel system.
Some signs that your fuel pump may be failing include struggling to accelerate, especially on the highway, and your car not starting.
