If your car is not starting, it is stalling, idling, and showing warning signs. Congratulations, you are dealing with a bad fuel pump relay.
These are the nine most common symptoms of a bad fuel relay.
- Check Engine Light
- Car Won’t Start
- Rough Idle & Engine Stalls
- Bad Fuel Pump
- Poor Engine Performance
- Silent Fuel Pump Noise
- Burnt Fuel Pump Relay
- Exhaust System Issues
- Variable Fuel Consumption
This article will tell you about nine bad fuel pump relay symptoms. In addition to that, we will also tell you what causes a fuel pump relay to fail, how to test a failing fuel pump relay, and its replacement cost.
Table of Contents
What is a Fuel Pump Relay?
As it is clear from the name, the fuel pump relay has to do something with fuel. The fuel pump relay controls the fuel pump, to be precise.
For the proper functioning of a vehicle, an adequate supply of fuel is required. When you turn on the car, the fuel is delivered through the fuel tank to the combustion chamber.
But fuel has to pass through several components during this journey.
The injectors will then spray this fuel into the combustion chamber.
Since the fuel pump is an electrical component, there is a need to control its current supply. Only then can you ensure its smooth operation. The fuel pump relay works here and controls the fuel pump.
Where is a Fuel Pump Relay Located?
Fuel pump relay is like other fuses in your car. It is usually located in the fuse box. Now, your vehicle’s fuse box can be in two different locations depending upon its make and model.
It might be under the hood by the side of the firewall. Or it can also be under the passenger side of your cabin under the dashboard.
You are looking for a black box that probably has a plastic covering. A new world of fuses, relays, and switches will appear when you open this box.
A wiring diagram indicates the name of each relay and fuse on the fuse box cover.
In case you are wondering, if you have stumbled onto the correct fuse box, you can check it on the wiring diagram.
What Causes a Fuel Pump Relay To Fail?
Fuel pump relay can fail due to two main reasons. Following are the two leading causes of a fuel pump relay failure.
Too Old Vehicle
Most of the problems in vehicles are caused due to their old age. If your car has high mileage and is driven over 200k miles, then the chances of encountering a fuel relay failure are multiplied.
When the vehicle gets old, the electrical wiring gets more twisted. The age of most components is reached as well. Hence, they are more likely to fail.
The second most common reason due to which the fuel pump relay fails is a weak battery. A weak battery will not be able to generate enough voltage. An adequate supply of voltage is required for the smooth operation of your car’s fuses, relays, and electrical devices.
A weak battery will not only bar sufficient voltage from reaching the electrical components, but it can also cause electrical power surges that can damage relays.
Thus a weak battery becomes the chief reason behind a malfunctioning fuel pump relay.
Bad Fuel Pump Relay Symptoms
It is very important to keep an eye on the symptoms of a bad fuel pump relay.
Let us dig deeper into the signs of a bad fuel pump relay.
1. Check Engine Light
Check engine light (CEL) illumination is the first and foremost sign you will receive as soon as some electrical system component goes bad.
Nearly all components of the car’s electrical system are connected to its functioning brain, which is the electronic control unit of the vehicle, otherwise known as the ECU.
The ECU receives signals from each of these components and gives divided instructions based on the inputs received from various sensors.
When any relay is malfunctioning or goes out, the ECU will know it in a split second. And the first thing the ECU does is it will illuminate the check engine light on your dashboard.
This is how you would know that something has gone bad with some component of your car.
For me, CEL is not the best symptom to diagnose any fault in your car. The reason is that there are about 50 different problems that can cause CEL to come on.
So you still have to look out for other symptoms of a bad component to narrow down the issue.
But the check engine light is not something you can ignore. As it sits right under your nose!
2. Car Won’t Start
Fuel pump relays are responsible for starting your car as well. When a fuel pump relay goes bad it will cause problems for your vehicle while starting.
When you turn on the ignition key, multiple systems of your car are activated. The fuel delivery system is among them. Fuel pump plays the most critical role in starting your vehicle by pressurizing the fuel system.
And we all know that a fuel pump relay is on the back of a fuel pump. You can never have a properly functioning fuel pump without a fuel pump relay that is in sublime condition.
The fuel pump pressurizes the fuel delivery system, and the pressurized fuel will reach the injectors. From here, it is sprayed in the combustion chamber to carry out the engine cycle.
Thus, if you feel any difficulty while starting your car, make sure to check your fuel delivery system. Most importantly, the fuel pump relay.
3. Rough Idle & Engine Stalls
A faulty pump relay can cause rough idling and stalling in your car. A failed fuel pump relay will not be able to maintain an adequate supply of fuel.
In this scenario, when your car is standing idle on a signal or otherwise, you will hear rough sounds coming out of the engine. As if the engine is not receiving enough fuel.
Similarly, when the fuel pump relay is not working fine, you will experience engine stalling. When you are traveling on a highway, and the car is moving at high speed, suddenly it will lose power. You would feel that the engine is not working anymore.
It happens due to a cut-off in the supply of fuel. This cut-off is initiated due to a faulty relay.
4. Bad Fuel Pump
The main job of a fuel pump is to deliver fuel from the gas tank to the fuel injectors and pressurize it whenever required. The average life span of a fuel pump is about 100,000 miles. But a bad fuel pump relay can cause it to fail way before that.
Hence, if your fuel pump has gone bad and you are considering replacing it, you must check the relay as well.
A bad relay can send too much current to the pump, causing its failure. Watch out for this symptom!
5. Poor Engine Performance
The engine of an automobile runs on a mixture of air and fuel. The gasoline engine has a fixed air-fuel ratio. If this ratio is disturbed, then the proper functioning of the engine is compromised. Lesser fuel supply would have different consequences, and more would have different.
The fuel pump relay ensures that an adequate current is supplied to the fuel pump. Which will then send the proper amount of fuel to the injectors. For some reason, if the relay has gone bad, the chances are that proper current flow is not reaching the pump.
As a result of which, the fuel supply to injectors is compromised. Lesser fuel supply would mean poor engine performance.
6. Silent Fuel Pump Noise
When a car’s fuel pump is operational, it makes certain noise. Especially when you are starting the car, the fuel pump has to perform the important task of pressurizing the fuel delivery system. Hence, it pumps fuel with even more pressure.
This creates more noise, and you must hear it. However, in the case of a faulty fuel pump relay, the proper current does not reach the pump.
Thus, it will not operate at its maximum working capacity. Due to this, the fuel pump will run silent, and you will not hear its noise while starting the car and accelerating it.
If you feel that the car has become unusually silent and you do not hear the pump’s noise, it is time to visit a car care center.
7. Burnt Fuel Pump Relay
This is the most apparent symptom of a bad fuel pump relay. It might be possible that excess power supply has burnt the pump relay. If you are feeling other signs of a bad fuel relay, then you must inspect the relay visually during regular maintenance of the car.
If there are signs of burning around it, you must conduct a test on it.
8. Exhaust System Issues
We have discussed the repercussions of undersupply of fuel. But a malfunctioning pump relay can also deliver more fuel than required. The engine’s combustion chamber is set to burn only a limited amount of fuel.
If more fuel reaches the combustion chamber, it will remain unburnt at the end of the engine cycle.
The Exhasut system of an automobile is used to receive combustion gases. Entry of any other product, such as unburnt fuel, can clog your car’s exhaust system.
Hence, if you notice unburnt fuel in the muffler and you are facing exhaust system issues frequently, you must inspect the fuel delivery system of your car. Get your vehicle inspected for a faulty pump relay.
9. Variable Fuel Consumption
Your car’s fuel consumption becomes variable when the pump relay goes bad. A faulty relay can inject too much or too little fuel into the combustion chamber.
This would mean that your engine will run lean sometimes and rich at others. Thus, if your car’s fuel consumption becomes variable, then it is an indication of fuel pump relay failure.
Fuel Pump Relay Replacement Cost
The average replacement cost of the fuel pump relay is between $45 and $165. The fuel pump relay itself is pretty cheap. You can find it in any regular auto store for $20 to $50.
The total labor cost for the replacement of the fuel pump relay is between $25 and $120.
Replacement of the pump relay is a straightforward job. It is as simple as swapping. You just get a new fuel pump relay from any auto store, locate your car’s fuse box, pinpoint the fuel pump relay from the wiring diagram, take out the old relay, and fit in the new one.
Mechanics tend to charge more in terms of labor for this 5 minutes job. The cost would even multiply if you own a luxury segment car.
You should really try to replace the fuel pump relay yourself!
The fuel delivery system is probably one of the most essential systems in your vehicle. Its proper functioning is necessary for the optimum performance of your engine.
The fuel pump relay is at the head of the fuel delivery system. It ensures that the right amount of fuel reaches from the fuel tank to the injectors.
The fuel pump relay is basically the brain of the fuel pump. Upon receiving a signal from the ECU of the car, it generates a current signal to operate the fuel pump and supply the required amount of fuel.
A defective fuel pump relay reveals itself in a number of other ways. Engine stalling, rough idling, and poor performance of vehicles are on top of that list.
A fuel pump relay plays a critical role in starting your vehicle as well. You should watch out for that as well.
If an excess amount of fuel is delivered to the combustion chamber, it may produce harmful combustion gases. Hence, if you observe other symptoms of a bad fuel pump relay, you must act immediately and get it replaced.
Frequently Asked Questions
What is the average life span of a fuel pump relay?
All relays and sensors are designed to last the lifetime of your car. In fact, all electronic components of your vehicle, including sensors and switches, should not fail. But that is not the case on most occasions.
These electrical components tend to malfunction due to power surges and fluctuations in the current supply. Issues in the electrical system shorten the lifespan of relays.
But even after all the issues, your fuel pump relay should last 100k miles.
Can you bypass a failed fuel pump relay?
Yes, you can bypass a failed fuel pump relay. It is just like directly connecting wires instead of installing a switch between them.
You can easily get a jumper cable and switch assembly from the market. You may use it to turn the fuel pump on and off manually.
But it isn’t recommended to use this method of bypassing the fuel pump relay for too long. Because the manual switch cannot communicate with the ECU of the car. It can never sense the fuel requirements of your engine.
This solution is only for the case where you are stranded in a distant place and cannot find a fuel pump relay. Other than that, it is a bad idea to bypass the fuel pump relay.
How long can you drive with a failing fuel pump relay?
It would depend upon the severity of the problem. You can drive somewhere between a few to several hundred miles.
If the fuel pump relay is slightly malfunctioning, then you would face the issue of occasional engine stalling and rough idling. You can tolerate this condition and drive with it for some time.
However, if your car is posing problems while starting most of the time. Plus, engine stalling and idling have become worse then you should not drive more than 10 or 20 miles.