In this article, we take a look at the common symptoms of a bad fuel pump. If your car won't start or keep dying, there is a good chance you have a bad fuel pump.
A failing fuel pump will show one of the following signs:
- Car won't start
- Engine stalling,
- Engine runs rough
- Car hesitates to start
- Engine hesitates at high RPMs
- Poor gas mileage, high fuel consumption
- Engine cranks then shuts off
How do you know the fuel pump is failing
There are a few signs that a fuel pump is on its way out.
First, a whining noise can be heard coming from the fuel tank. Furthermore, your vehicle may experience performance problems.
For example, there may be a misfire due to low fuel pressure. Your car may also die when you step on the gas pedal. That means fuel is not keeping up with demand. Moreover, Your car may also hesitate when giving it gas.
This problem can be caused by a bad fuel pump but also due to a clogged catalytic converter.
Troubleshooting a bad fuel pump
The car will not start
The first thing you should do check is to verify the fuel pump is working. One way to do this is to listen for a humming noise coming from the fuel pump. The fuel pump is typically located right below the rear seat.
If you turn on the ignition, you should hear the fuel pump engage for about 15 seconds with the ignition on.
The fuel pump is located in the fuel tank which is located in the back of the vehicle. Turn the key to on position and turn off your radio. You will listen for a humming noise. The fuel pump will prime for 2 seconds then turn off.
At this point, you should be able to hear the fuel pump run. If you do not hear the fuel pump humming go step #2.
Crankshaft Position Sensor
Note that a bad crankshaft position sensor may exhibit similar symptoms where car will not start. When the CPS fails you often will have a hard time starting the car when the engine is hot.
Check fuel pressure
There are a few ways to check for fuel pressure. For this step, you will need a fuel pressure test kit.
First, locate the shredder valve located on the fuel pressure rail.
Connect a fuel pressure gauge to the fuel pressure shredder valve. Turn the key to on position.
This will activate the fuel pump. If there is fuel pressure the fuel pump is functioning properly. Check the fuel pressure specification online or use your manual that came with your car.
Most fuel pressure on a car run between 35-55 psi. If you do not have a fuel pressure gauge, you can simply get a screwdriver and push down the pin on the shredder valve. Some fuel should be released. Be mindful not to get fuel in your eyes. Maintain distance. If there is no fuel pressure, go to step #3.
Use a digital multimeter to check for a blown fuel pump fuse. Located the fuse box. Usually, it is mounted in the engine bay by the side or sometimes underneath the steering wheel.
Check the fuse by using a test light. Put the test light on the negative side of the battery and touch the terminal on top of the fuse.
The test light should light up on both sides on top of the fuse. If the test light does not light up, remove the fuse and inspect it. If it is blown, replace it. Next, check the relay.
Check fuel pump relay
Fuel pump relay may have failed in which case no power is sent to the fuel pump. Checking the fuel pump relay is a simple procedure that you can perform using a digital multimeter.
Fuel pump relays are usually four posts and very inexpensive to replace.
Check for power at the fuel pump
The next step would be to check for power at the fuel pump. Unplug the wire harness from the fuel pump.
Connect a digital multimeter to the plug and turn on the ignition. You should read 12-14 volts at the fuel pump.
Read Fault Codes
If you have a code reader read the fault codes from the ECU. A current diagnostic trouble code or even stored codes can help you figure out why the engine won't start.
Read this guide, to learn more about OBD2 scanners.