To test your fuel pump relay in five easy steps, first notice if your engine struggles to start or stalls, which can indicate relay trouble. Next, find the relay in the fuse box and check its terminals.
Before testing your fuel pump relay, you need to recognize the signs that it might be faulty. You’ll notice your engine struggling to start or not starting at all, which is a common symptom.
Identify Signs of a Faulty Fuel Pump Relay
Before testing your fuel pump relay, you need to recognize the signs that it might be faulty. You’ll notice your engine struggling to start or not starting at all, which is a common symptom.
You might hear a clicking noise from the relay when you turn the ignition, but the fuel pump doesn’t activate. Your vehicle could also stall while driving, indicating inconsistent fuel delivery.
Locate the Fuel Pump Relay and Identify Its Terminals
You might hear a clicking noise from the relay when you turn the ignition, but the fuel pump doesn’t activate. Your vehicle could also stall while driving, indicating inconsistent fuel delivery.
Another sign is a sudden drop in fuel efficiency or engine misfires. If your dashboard’s check engine light comes on, it might be related to the relay or fuel system.
Spotting these symptoms early helps you avoid being stranded and lets you address the issue before it worsens. Keep these signs in mind as you prepare to test the relay.
Keep the relay’s diagram handy, as it will guide you during the testing process.
Spotting these symptoms early helps you avoid being stranded and lets you address the issue before it worsens. Keep these signs in mind as you prepare to test the relay.
Finding the fuel pump relay is your next step, and it’s usually located in the fuse box under the hood or inside the cabin.
Use a Multimeter to Test the Relay Coil Resistance
Check the fuse box cover or your vehicle’s manual to spot the exact location. Once you find the relay, remove it carefully.
You’ll notice several metal terminals at the base—these connect the relay to your car’s electrical system. Typically, there are four or five terminals, each serving a specific function like power input, ground, and control signal.
The terminals are often numbered or labeled, so take a close look. Identifying these terminals correctly is essential because it helps you test the relay properly.
If the reading is considerably higher or shows infinite resistance, the coil is faulty.
The terminals are often numbered or labeled, so take a close look. Identifying these terminals correctly is essential because it helps you test the relay properly.
Keep the relay’s diagram handy, as it will guide you during the testing process.
Attach probes to coil terminals (85 and 86)
With the fuel pump relay removed and its terminals identified, you’re ready to check the coil resistance using a multimeter. This step helps determine if the relay coil is functioning properly or if it’s damaged.
First, set your multimeter to the ohms (Ω) setting. Then, connect the probes to the coil terminals—usually marked as 85 and 86. A healthy relay coil typically shows resistance between 50 and 120 ohms, but check your vehicle’s specifications.
If the reading is considerably higher or shows infinite resistance, the coil is faulty.
Compare reading to vehicle specs
If the reading is considerably higher or shows infinite resistance, the coil is faulty.
Start by reconnecting the fuel pump relay and turning your vehicle’s ignition to the “on” position without starting the engine.
Practical Checks
- Set multimeter to ohms (Ω)
- Attach probes to coil terminals (85 and 86)
- Compare reading to vehicle specs
- Identify if coil is open or shorted based on resistance
- Disconnect the negative battery cable for safety
- Find and remove the defective fuel pump relay