5 Symptoms of a Bad Fuel Pump Relay (& Replacement Cost)

The fuel pump relay is switching power to the fuel pump on and off. But how to tell if the fuel pump relay is bad? Read on to learn the most common signs!

Symptoms Of A Bad Fuel Pump Relay

The fuel pump relay is an important component of the fuel system of your vehicle.

The fuel pump relay gives the fuel pump power when it is time to build up fuel pressure in the rail. Whenever you turn on the ignition of your vehicle, the fuel pump relay is turned on.

There are different reasons due to which the fuel pump relay fails. In this article, we will discuss symptoms that your fuel relay failed, location, replacement cost, and how to diagnose it. Let’s begin with a quick overview of the signs to look for.

The most common symptom of a bad fuel pump relay is a stalling or dead engine. You will probably see these signs along with a check engine light on your dashboard. You can also notice signs like rough acceleration.

The relay can fail due to many reasons, from dust to electrical power surges, anything can affect the well-being of a fuel pump relay.

Here is a more detailed list of the most common symptoms of a bad fuel pump relay.

Bad Fuel Pump Relay Symptoms

1. Check Engine Light on

Check Engine Light

The engine control module does always monitors all engine sensors to ensure they do not show the wrong values. If the ECU suspects a wrong value from any sensor, it will light up the check engine light. A check engine light is also the most common sign of all bad fuel pump symptoms.

The ECU monitors the fuel pressure with the help of the fuel pressure sensor. If the fuel pump relay suddenly fails, it will light up the check engine light and store a trouble code on the fuel pressure.

RELATED: Symptoms of a Bad Main Relay

2. Rough Acceleration

Slow Acceleration

The fuel pump relay going bad can affect the fuel pump’s power and affect fuel delivery to the engine. An engine runs on fuel just like the heart of a human runs on oxygen and blood.

Therefore, any fuel pump relay issues will affect fuel flow to the combustion chamber, and your vehicle might have problems starting.

However, this can happen due to several other reasons, such as a choked fuel filter, so you should always properly diagnose your car before replacing any parts.

3. Engine Stalling

Engine Stall

If the fuel pump relay may have any bad solderings inside it, it might suddenly lose the relay connection and stop delivering power to the fuel pump.

The engine turns off if the combustion chamber’s fuel is inadequate or doesn’t have the proper pressure.

The part that ensures none of this happens is the fuel pump, and it cannot work perfectly if the fuel pump relay develops any issues.

4. Engine is completely dead

Dead Car After Road

A faulty fuel pump relay can also cause the engine not to start at all and be completely dead. No fuel pressure means that your engine will never start, and if the fuel pump relay failed, it would not give any power to the fuel pump to build up fuel pressure.

5. No noise from fuel pump on ignition

Starting Car

When you turn the ignition on in the ignition lock, you should hear a whirring noise from the rear of the car. This means that the fuel pump started building fuel pressure in the fuel rail.

If you cant hear this, there might be a problem with the fuel pump relay. You can try to listen closer around the fuel tank for any noise for 2-3 seconds after turning the ignition on.

Where is the Fuel Pump Relay Located?

Relay Fuse Box

In most car models, the fuel pump relay is located in a fuse box somewhere under your dashboard, but it can also be located in the fuse box in the engine bay.

The engine’s or the dashboard fuse box is usually a long black box containing a fuel pump relay and various other fuses and relays. For different vehicles, the fuel pump relays can be located in different places.

Check your repair manual for getting the exact location of the fuel pump relay fast.

Fuel Pump Relay Replacement Cost

The average fuel pump replacement cost is between $90 and $150, depending on the car model and labor costs. The parts may cost you between $20 and $50, while the remaining cost is labor.

The fuel pump relay is a small electronic device easily acquired online or at the nearest spare parts shop. The fuel pump relay’s replacement cost involves the cost for the parts and the labor cost that the mechanic would charge you.

When considering the labor cost, it could be at least an hour of work or more in certain cases.

Depending on your mechanic’s hourly pay rate or the per hour cost, the repair shop would charge you; the labor cost may differ. Apart from the labor cost, the fuel pump relay is not a very expensive device, and you can buy one for $20 to $50 on average for most vehicles.

Fuel Pump Relay Diagnosis

Bad Soldering Relay

Diagnosing a relay is often pretty straightforward. The fuel pump relay does often have 4 pins, and in this case, it is often easy. If your relay has more pins and not the same numbers mentioned here, you need to check a wiring diagram.

  1. Locate the fuse box and locate the fuel pump relay
  2. Lift it and check under it for the numbers 30, 85, 86, and 87. If you locate these numbers, you can put the fuel pump relay back.
  3. Put the relay back so you can reach the pins with a multimeter while you cycle the ignition.
  4. Turn on the ignition and check pin 87 with a multimeter. If you get voltage there, it may tell you that the fuel pump relay is working, but it can also have intermittent problems.
  5. If you do not get voltage there, make sure that you have constant voltage on Pin 30 with the ignition on. If you don’t, there might be a problem with a broken fuse. You should also have constant voltage on pin 85, and pin 86 should be grounded from the engine control unit when you turn on the ignition.
  6. If you found any problems with the relay, you can remove the case from it to check for any bad solderings. Resolder the relay if you find any problems.