Katerina Swanson
A faulty fuel pump can cause a lot of inconvenience, especially when you're in a hurry. To avoid this, it's important to know how to check your fuel pump for any issues. The first step is to determine if the problem is fuel-related, which can be done by having an assistant crank the engine while you spray. If the engine starts momentarily, then the issue is likely related to fuel. Next, you can check the fuel pressure with a mechanical fuel pressure gauge, which is inexpensive and readily available. If the needle doesn't move or barely moves, it could indicate an issue with the fuel pump. Additionally, you can check the fuel pump fuse and voltage to ensure it's receiving power. If the pump isn't working, there could be a blockage or leak in the fuel line, or the pump itself may be sealed and beyond repair. It's important to perform a thorough diagnosis to ensure the pump is the problem before replacing it.
| Characteristics | Values |
|---|---|
| Location of the fuel pump | In the fuel tank |
| What to check | Fuel pump fuse, fuel filter, fuel pressure, carburettor, fuel pipes, fuel pump relay clicking, wiring harness, voltage, diagnostic trouble codes (DTCs) |
| Tools required | Fuel pressure gauge, scan tool, code reader, rubber hose, bucket |
| Possible issues | Blown fuse, high amp draw, direct short, blockage, leak, loose mountings, worn-out electric fuel pump |
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What You'll Learn
Check for a blown fuse
A blown fuse can lead to inconvenience and security issues. A fuse is typically a metal wire strip that melts or burns when too strong a current passes through it, thus interrupting the flow of electricity and breaking the circuit to a device. A car has many such fuses to protect its various electrical components from high-voltage occurrences. These fuses are generally rated at 32 volts and are in one of two fuse boxes for most vehicles. When a component in a vehicle stops working, the reason is often a blown fuse due to an overabundance of electrical current.
To check for a blown fuse, first, turn off the vehicle and locate the main fuse box, usually located in the driver’s side footwell underneath the dashboard. There may also be a second fuse box under the hood or in the engine bay. Refer to your manual to find the fuse box and fuse diagram. In most cases, the fuse box is located under the hood near the steering wheel (under a plastic cover).
Once you've located the fuse box, remove the fuse panel’s cover to reveal different colour-coded fuses with stamped amperage ratings. Identify the problem using the fuse diagram, which should be in your manual too. If you know you’re having an issue with your radio, for example, search for a fuse labelled “radio”, pull it out and inspect it visually to see if the wire is broken. Car fuses are translucent, so hold the fuse up to a bright light and look inside. If the upside-down U-shaped wire inside the fuse is cut, separated, melted, burnt, or broken, the fuse is blown.
You can also use diagnostic tools like a test light or a multimeter to identify a blown fuse without having to pull it out. If you find a blown fuse, try replacing it and starting the vehicle. If the fuse blows again, a direct short is present and will need to be diagnosed by a mechanic.
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Test fuel pressure
Testing fuel pressure is an important step in troubleshooting issues with your car's fuel pump. Here is a detailed guide on how to test fuel pressure:
Firstly, ensure you are wearing the appropriate safety gear and working in a well-ventilated area. Fuel vapours are highly flammable, so it is crucial to take the necessary precautions. Put on safety glasses and gloves, and ensure you have a fire extinguisher nearby.
Now, let's begin the testing process:
- Start your car and let it idle.
- Install a fuel pressure gauge. This gauge will connect to the fuel system, typically consisting of a gauge attached to a fuel hose with multiple fittings.
- Run the fuel pump.
- Note the pressure reading on the gauge.
- Compare the reading to the manufacturer's specifications. If the pressure is within the recommended range, your fuel pump is likely functioning correctly. If the pressure is too low or too high, it could indicate a faulty fuel pump or another issue with the fuel system.
- If the pressure is low, you should address that problem first.
- If the fuel pump is supplying sufficient pressure, perform a fuel volume test to ensure the proper amount of fuel is being delivered to the fuel injectors.
An alternative method to test fuel pressure without a gauge is as follows:
- Locate the pressure test valve near the fuel pump. It may resemble a tire valve.
- With the car turned off, press the valve to see if fuel squirts out.
- Turn the car to "ON" for a few seconds and then turn it off. Try pressing the valve again to compare the results.
Remember, if you are unsure or uncomfortable at any point, it is best to consult a professional mechanic for assistance.
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Check for carburettor faults
To check for carburettor faults, you can perform the following tests:
Firstly, ensure that fuel is getting to the inlet barb of the carburettor. Check that it is not being blocked by a clogged fuel filter, a kink in the line, or some other obstruction. You can do this by turning or removing the drain plug to see if fuel is entering the bowl. If the bowl is filling, you may have a stuck float valve, a clogged passage, or a plugged jet. In this case, disassembling the carburettor for a thorough cleaning is advised.
Secondly, with the engine warmed up and idling, remove the air cleaner and look down the throat of the carburettor at the main nozzle. If it is wet or dripping with gasoline, the float level is likely too high, which can cause fuel to discharge while the engine is idling.
Thirdly, if the engine idles roughly after warming up, the idle system could be at fault. Open the throttle slowly until the engine is running at around 3,000 rpm. If the speed does not increase steadily and the engine runs roughly, the idle or main-metering system is likely defective.
Finally, with the float bowl full, the air cleaner removed, and the engine shut off, look down the throat of the carburettor and quickly open the throttle. You should see the accelerator pump system discharge a squirt of fuel into each primary barrel. The flow should continue for a few seconds after the throttle valve.
Other signs of carburettor issues include excessive fuel consumption, rough idling, and hard starting.
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Inspect for loose mountings
Loose mountings are a common fault in fuel pumps. The pump is often out of sight, and bolts may work loose unnoticed. This will cause a severe oil leak.
To inspect for loose mountings, start by locating the high-pressure fuel pump in the fuel system. It may be necessary to remove other components to access the pump. Once you have located the pump, carefully disconnect the fuel lines, electrical connections, and mounting bolts or brackets securing the pump. Inspect the mounting bolts or brackets for any signs of looseness or damage. If the mountings appear loose, this may be the source of the problem.
It is important to consult the appropriate service manual or seek assistance from qualified technicians for the specific engine and high-pressure fuel pump you are working on, as the exact steps and procedures may vary depending on the model and manufacturer.
If you determine that loose mountings are the issue, you can attempt to tighten the bolts or brackets to secure the pump. However, if the mountings are damaged or if there are other issues with the pump, it may be necessary to replace the entire pump.
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$15.89
Listen for the fuel pump
Listening for the fuel pump is a simple way to check for fuel pump circuitry issues. It is important to note that the absence of noise from the fuel pump does not necessarily indicate a faulty pump, but rather that there may be an issue with the Fuel Pump/Sending Unit circuit.
To listen for the fuel pump, you will need an assistant to turn the key to the "On" position while you listen near the gas tank opening. It is important to ensure that the vehicle is turned off and safely parked on a level surface. Clearly instruct your assistant that they are not trying to start the car, but simply turning the key so that the lights come on.
A functioning fuel pump will typically make a low-humming noise, which you should be able to hear coming from the gas tank area. If you do not hear this noise, it could indicate an issue with the fuel pump or the pressure regulator. To make it easier to hear the noise, you or your assistant can place a funnel, preferably a long transmission funnel, into the fuel tank filler neck.
If you hear the noise, but it sounds more like a whine or a drone, it could be a sign that the fuel pump is wearing out. Additionally, if you experience a long crank time after letting the car sit, it usually indicates an issue with the pump or pressure regulator.
While listening for the fuel pump is a helpful initial diagnostic step, it is important to perform a thorough diagnosis to ensure that the pump is the problem before replacing it.
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Frequently asked questions
Checking your fuel pump is not a very dangerous task but safety should always come first. Park your vehicle on a level surface, making sure it is turned off. Next, remove the fuel cap and locate the fuel pump test point. Get a fuel pressure gauge and hook it up to the test point. Then, have an assistant rev the engine and check the gauge. If the needle doesn't move, you've found the problem.
If your car stops running and has not run out of petrol, check whether there is petrol in the carburettor. If there is not, there is a fault in the fuel system. Another sign of a faulty fuel pump is if your car has trouble accelerating. This could be because the filter is clogged with sediment.
Check your owner's manual for the location of the fuse box. Then, find the fuse that corresponds to the fuel pump and inspect it for signs of failure. If the fuse is blown, it will be broken or burned. If it looks good, check the rest of the fuses related to the fuel system and replace them if necessary.
If you have a blown fuse, try replacing it and starting your vehicle. If the fuse blows again, a direct short is present and you will need to take your car to a mechanic.
