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 why the fuel pump relay fails. In this article, we will discuss the symptoms to know if your fuel pump relay is bad, its location, replacement cost, and how to diagnose it. Let’s begin with a quick overview of the signs to look for.

Symptoms Of A Bad Fuel Pump Relay

The most common symptoms of a bad fuel pump relay are a stalling engine, performance issues, and a check engine light on your dashboard. If your car won’t start at all and you can’t hear the fuel pump when you turn on the ignition, it could also be due to a bad fuel pump relay.

The relay can fail for 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 signs of a bad or failing fuel pump relay to look for:

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 relay 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.

Frequently Asked Questions

Can you run a fuel pump without a relay?

You can, but it’s definitely not recommended. If you just want to test the fuel pump, you can bridge the relay to see if the relay is bad. But if you plan on driving around without the relay for a fuel pump and wiring it directly, that’s a bad idea. Fuel pumps require a lot of power, and if you install an on/off switch on the wire directly to the fuel pump, it will probably melt the switch.

Will a bad fuel pump relay throw a code?

Yes, a bad fuel pump relay can throw a code, but that depends on the model of the car you drive and how advanced the on-board diagnostic system is. If the car throws a code on the fuel pump relay, the code will most likely be P0230, indicating that there is something wrong with the power to the fuel pump.

Can a bad fuel pump relay cause a car not to start?

Yes, a bad fuel pump relay can cause a car not to start, and it’s actually a quite common cause. The fuel pump relay is responsible for supplying power to the fuel pump, and if it goes bad, the car will not be able to start.

Can you clean or fix a fuel pump relay?

Yes, a relay can be cleaned and resoldered, but it requires some knowledge. You will need to take the relay apart and resolder and clean all of the parts and then put it back together. Fuel pump relays are often quite cheap, so in most cases, it’s better just to buy a new relay.

Conclusion: Bad Fuel Pump Relay Symptoms

The main symptoms of a bad fuel pump relay include:

  • Check engine light on
  • Rough acceleration
  • Stalling engine
  • Engine is completely dead
  • No noise from fuel pump on ignition

If your car has any of these bad fuel pump relay symptoms, it’s probably time to take it to a mechanic. Don’t wait until it’s too late and you’re stranded on the side of the road. Ignoring it can also cause other issues.

If you feel you have the knowledge yourself, you can test the fuel pump relay with a multimeter to ensure it is working properly. If not, it could be due to cracked solder inside it!

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Magnus Sellén
Written by:

Magnus is the owner and main author of Mechanicbase. He has been working as a car mechanic for over 10 years, and the majority of them specialized in advanced car diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.