Home » Guides » How to Test a Fuel Pump Relay With Multimeter? Guide Of 2023

How to Test a Fuel Pump Relay With Multimeter? Guide Of 2023

By shafiq usama

As an electrical engineer, I love explaining how things like circuits and electronics work. I write on my blog to share simple explanations, reviews, and useful tips about the latest technology.

Testing the fuel pump relay on your car is a relatively simple process that can be done with a multimeter. In this automotive guide, we'll walk you through the steps of how to test a fuel pump relay with multimeter. This is an important step for anyone who is interested in doing their own automotive repairs!


What is a fuel pump relay and what does it do?

The fuel pump relay is an electronic switch that controls when your vehicle's engine turns on and off. A faulty or broken pump will prevent gas from getting to combustion chamber. If your car is having trouble starting, this is likely the first place you'll want to look.

Most of the time car batteries also fails to perform therefore its important to check your car battery properly. Now let's get started to our fuel pump testing guide

How to test a fuel pump relay with multimeter? 4 Simple Steps

How to Test a Fuel Pump Relay With Multimeter

A step by step guide

You'll need a multimeter to test the fuel pump relay. How do you know if your current one is working properly? If it's been more than five years since its last calibration, then it's time for an upgrade!

STEP 1

First of all, disconnect battery power before testing anything electrical in your car. It may be helpful to get someone to help you hold the battery in place while you're working on the other components.

STEP 2

Now, locate your fuel pump relay. It will be a small black cube-shaped box with a few wires coming out of it. The easiest way to identify it is by looking for the hot wire. That's always hot (meaning it has power running through it) even when the engine isn't running. This is called an ignition switch wire.

STEP 3

To test if there's voltage coming from your fuel pump relay, connect one end of a jumper lead to the positive terminal on your battery. After this touch the other end briefly against each pin in turn until you find one that sparks or lights up brightly for about half a second. If not, then you'll have to replace your fuel pump relay or check other components of the vehicle. These components can be an alternator or starter motor or your car battery. I have also made a a list of best car battery testers for you.

STEP 4

If all else fails, it could also mean there's something wrong with one of the wires leading from your battery- so try using another jumper lead instead and see if that changes anything. I make the list of best budget multimeters you can check this.


Common symptoms of a bad fuel pump relay

If you're experiencing any of these symptoms, it's best to take your car to a mechanic for further diagnosis. Testing the fuel pump relay is just one step in finding out what might be wrong with your vehicle.

How to Test a Fuel Pump Relay With Multimeter
  • Car won't start
  • Engine turns over slowly or not at all
  • Lack of power while driving

Testing it is a quick and easy way to figure out what's wrong with your car and could potentially save you from an expensive trip to the mechanic. If you want to know how to check car fuses with multimeter then I have also made a separate guide about that. Its difficult for most of the engineers and automotive technicians to find a suitable multimeter on a budget. Therefore, to make it easier and cheaper I have compiled a list of best automotive multimeters for you.


How to replace a fuel pump relay?

If you've determined that your fuel pump relay is bad, it's time to replace it. How do you go about doing this? There are two ways: with a multimeter or without one (which is the easier option).

  • To begin, disconnect battery power before testing anything electrical in your car. It may be helpful to get someone to help you hold the battery in place while you're working on the other components. If you have corroded battery then replace it first.
  • Now, locate your fuel pump relay. It will be a small black cube-shaped box with a few wires coming out of it. The easiest way to identify it is by looking for the wire that's always hot (meaning it has power running through it) even when the engine isn't running- this is called an ignition switch wire.
  • If you don't have a multimeter on hand, then use a jumper lead (with one end attached to the positive terminal of your battery). After this touch each pin in turn until sparks or lights up brightly for about half a second. If not, then you'll have to replace your fuel pump relay or check other components of the vehicle that might be causing this problem like an alternator or starter motor.
  • If all else fails, it could also mean there's something wrong with one of the wires leading from your battery- so try using another jumper lead instead and see if that changes anything.

Tips for preventing future problems with the fuel pump relay

If you've had to replace your fuel pump relay, then it's important to remember that this isn't a one-time fix. How do you keep the problem from happening again? You can prevent future problems by making sure all wires leading into or out of the fuel pump relay are secure and not frayed at their ends where they could easily short out. You should also avoid allowing water or dirt to build up in the relay box- so keep it clean and dry. 

preventing future problems with the fuel pump relay

These are just a few tips to help you prevent future problems with your fuel pump relay. If you want to check car relays of all types in your car then I have also made another automotive guide for you. If you're still experiencing issues after following these guidelines, then it's best to take your car into a mechanic for further diagnosis.


Safety Guidelines while Testing Fuel Pump Relay

Testing the fuel pump relay is a fairly simple process, but there are still some safety points you should keep in mind. Here are five of them:

  • Make sure to disconnect battery power before testing anything electrical in your car
  • Always use jumper leads with someone helping you hold the battery in place
  • Avoid touching any wires that might be hot
  • Keep the area around the fuel pump relay clean and dry.

Final words

Hopefully, this guide about how to test a fuel pump relay with a multimeter  helps you in tracking and removing automotive faults. Share this guide with your loved ones so they can tackle issues on their own.