Are you a DIY’er who likes to do your own vehicle repairs? If so, and you’re looking for information about how to diagnose and replace a fuel pump, we can help. We have a ChrisFix video and some valuable text that will show you exactly how to do just that.
How do I diagnose a faulty fuel pump?
- Test fuse and power to fuse box
- Test power to fuel pump and inertia switch
- Check fuel pump relay
- Test fuel pressure
- Remove parts surrounding fuel pump
- Remove old fuel pump, install new fuel pump
This is a quick overview of how to diagnose the fuel pump in a vehicle. We also have Chris’s video and some detailed step-by-step text that will show you exactly how to diagnose and replace a fuel pump.
So, keep reading.
What to Check Before Replacing the Fuel Pump
Take your key, put it in the ignition, and put it in the run position. Listen for a hum or a whine from the fuel pump in the rear of the vehicle. That hum or whine that you will hear for a few seconds when you first turn the vehicle on is normal and is what you should hear.
1. Fuse and Fuse Box
If you don’t hear that hum or whine, it doesn’t necessarily mean the fuel pump is bad. It could be something as simple as a bad fuse. So, get the owner’s manual and turn to the page about fuses. Read where the fuse is for the fuel pump and locate that fuse. Then, you remove the fuse. If you don’t see any break in the connection the fuse is good. But that’s not all you need to check.
Grab a multi-meter and stick one prong into one side of the fuse holder and the other prong into the other side of the fuse holder. If the meter shows that it’s getting enough volts for your vehicle, that means the fuse box is getting enough power to it.
2. Power to the Fuel Pump
Next, you will need to see if you are getting enough power to the back of the vehicle where the fuel pump is by the gas tank. This is a little more involved than testing the fuse and fuse box. So be sure to watch Chris’s video so, you can see exactly how to test this.
If you do the test and find there is no power going to the fuel pump, you will have to do the following.
3. Power to the Inertia Switch
The inertia switch is located in the trunk. The inertia switch should be pressed down. But if something hits it, that could cause it to pop up. This switch is designed to cut the power to the fuel pump in case of an accident. So, if it’s popped up, you just press it back down.
4. Check the Fuel Pump Relay
The fuel pump relay location is different on every vehicle. So, you will need to find the location of that for your vehicle. When you turn the vehicle to the run position, you should hear a couple of clicks. This is the fuel pump relay. If you don’t hear those clicks, you should go ahead and change out the fuel pump relay. This is a relatively cheap part.
5. Test the Fuel Pressure
Take a fuel tester pressure gauge, take off the Schrader valve cap on the fuel rail, and screw on the gauge. Then turn the ignition to the run position and the gauge will tell you the exact fuel pressure.
The gauge should read at least 30 psi or a little higher and stay there.
If you don’t get any reading at all, that tells you for sure there is no fuel pressure at all and the fuel pump isn’t running. But it is getting voltage. So, you might think the fuel filter is clogged. However, if that was the case, you would see the pressure on the fuel gauge tester rise slowly or just a little bit.
After all the testing that shows everything you tested is working, you now know for sure you need a new fuel pump.
6. Prepping to Replace the Fuel Pump
When you are replacing a fuel pump, you should also go ahead and replace the fuel filter at the same time. Also, make sure you wear your safety goggles and that you have the proper fire extinguisher on hand since you are working with gas.
First, remove the negative battery terminal so the car won’t get any power. If you don’t, you could accidentally ground something out, it could spark, and ignite the fuel.
In some vehicles, you can access the fuel tank by lifting up the trunk carpet and removing the trunk boards. But if your vehicle doesn’t have that access, you will have to drop the fuel tank from underneath the vehicle. First, you will need to siphon out as much gas as you can. This will make the tank as light as possible.
There are quite a few steps for removing the fuel tank, fuel filter, filler neck, fuel lines, etc. So be sure to watch Chris’s video so you can see exactly how to do all that. Then you can move on to replacing the fuel pump. Chris also gives you some invaluable tips that will make the job a whole lot easier. So, don’t skip the video.
How to Replace the Fuel Pump
First, remove all the bolts that hold the fuel pump assembly in. Then pop the lid off. But be careful not to break any of the hoses. Now, look into the fuel pump assembly and there is a clip on each side. You will just push them inward with your fingers and pull the assembly out. Be careful not to bend the float or it could cause your gas gauge to not read accurately.
You now have two choices. You can replace the entire fuel pump assembly. In that case, you just drop the new assembly in and you’re good to go. Or, you could replace the fuel pump inside the assembly since that is the only thing that’s bad. And the latter is what Chris shows you in the video.
Here are the steps:
- Disconnect the wiring harness from the old fuel pump
- Remove the bolts that hold the pump in and remove the lid
- Pull out the fuel pump
- Get your new fuel pump and put the rubber piece on the top and the bottom just like the old one
- Get the fuel sock (pre-filter) and install it just like the old one
- Drop the fuel pump back into the fuel pump assembly and put the lid and screws back on
- The new fuel pump will come with a new wiring harness so install that
- Reinstall the fuel pump assembly back on the car and do everything you did to remove it, but do it in reverse
After you’ve done all that, put the key in the ignition and turn it to the run position and turn it off. You will do this three times in a row. That is the process that will pressurize the fuel and fill the fuel lines with gas. Now you can start the car.
It would be a good idea to watch Chris’s video again, or while you are doing this because there are so many steps involved. And, he has some extremely valuable tips that will help you get everything right.
If you get one thing wrong, you could do damage to the vehicle. Or, at the very least, you could end up with the check engine light on.
What’s Next?
If you want more information about any given vehicle, you can easily get its VehicleHistory report. This information can help you make educated decisions about any vehicle before you buy it.
