A bad fuel pump relay can be a frustrating and inconvenient problem for any car owner. This small electrical component plays a crucial role in starting and running your engine, so when it fails, it can leave you stranded.
In this guide, we’ll explore the symptoms of a bad fuel pump relay, discuss how to diagnose the issue and provide tips on fixing or replacing it.
What is a Fuel Pump Relay?
The fuel pump relay is a necessary component for the combustion engine model to function. The combustion engine needs fuel to run, and this component ensures that that engine gets what it needs. It is usually controlled by the ignition or the power control module.
When you turn on the ignition, it is activated and will supply electricity to turn on the fuel pump. When you shut off the ignition, it powers down the fuel pump.
Key Takeaway:
- The fuel pump relay is an electromagnetic switch that uses low current to control a higher current circuit.
- Some common symptoms of a failing fuel pump include ignition issues, the fuel pump running continuously, and an illuminated check engine light.
- The average cost for a Fuel Pump Relay Replacement is between $67 and $75. Labor costs are estimated between $30 and $38 while parts are typically priced around $37.
Location
In most vehicles, this relay can often be found in the fuse box in the engine bay, which is usually a long black box that contains the relay along with various other fuses and relays.
If you cannot find it, check your owner’s manual. The fuel pump relay can be located in different places on different cars: under the hood, on the firewall, or near the steering column, to name a few locations.
Function
When you turn the key in the ignition to start your car, the “start cycle” of the combustion engine begins. The fuel pump relay is activated long enough to supply the current required to turn on the fuel pump.
The key here is to produce a small amount of voltage but consistently to the fuel pump. Once the engine is running, the fuel pump relay shuts off.
At this point, the electricity for the fuel pump is supplied by the oil pressure-sending unit. When you shut off the ignition, the fuel pump relay is engaged again, long enough to power down and shut off the fuel pump.
Bad Fuel Pump Relay Symptoms
When the fuel pump relay goes bad, the fuel pump won’t work properly. As a result, you’ll notice one or more of the following symptoms.
Note: Because other problems can present the same symptoms as a bad fuel pump relay, you’ll want to perform a thorough diagnosis of the vehicle before replacing any parts.
#1. Engine Cranks But Doesn’t Start.
The most common sign of a bad fuel pump relay is an engine that cranks but doesn’t start. A fuel pump relay will typically fail in the open position, preventing voltage from reaching the fuel pump. As a result, the engine will be starved of fuel and refuse to run.
#2. Fuel Pump Runs Continuously.
Although somewhat rare, there are instances where the fuel pump relay can stick closed, causing the fuel pump to run continuously. The problem can happen in circuits that supply power to the fuel pump fuse at all times. In such a scenario, you’ll hear the fuel pump running continuously, even when the key is out of the ignition.
#3. Illuminated Check Engine Light.
On some vehicles, the engine computer, which is often referred to as the powertrain control module (PCM) monitors the fuel pump relay and its circuit. If the PCM detects a problem, it turns on the check engine light and stores a corresponding diagnostic trouble code (DTC) in its memory.
Code P0230 “Fuel Pump Primary Circuit” is one such code. Keep in mind, however, that this code is not supported by all makes and models. As such, not all vehicles will turn on the check engine light for a bad fuel pump relay.
How To Test A Fuel Pump Relay?
After visual inspection, if you cannot identify any possible culprit, continue to test your fuel pump relay to see if it has failed:
- Set your digital multimeter to the lowest range on the Ohms scale or set it to ‘continuity’.
- Connect one lead to one of the power circuit pins, and connect the other lead to the other power terminal.
- Your meter should read infinite resistance.
- If you detect zero ohms or any resistance value instead of infinity, your fuel pump relay has shorted power pins and needs to be replaced.
How Does A Technician Perform A Bad Fuel Pump Relay Replacement?
Fuel pump relay replacement can vary to some degree based on the vehicle make and model, but the process generally involves the following:
- Locate the fuse/relay panel that contains the fuel pump relay
- Remove any guards or covers necessary to allow access to the relay panel
- Open the splash-proof lid on the panel (if the panel is located inside the engine bay)
- Locate the location of the relay inside the panel and remove the relay
- Insert a new relay (specific to your vehicle) and return all components to their original condition
- In many cases, before replacing a fuel pump relay, a technician will remove the old relay and perform a bench test on it to determine whether or not the relay is bad and the cause of fuel system problems before replacing it with a new one.
The average cost for a Fuel Pump Relay Replacement is between $67 and $75. Labor costs are estimated between $30 and $38 while parts are typically priced around $37. This range does not include taxes and fees, and does not factor in your unique location.