Subaru WRX Dies After Starting Diagnosis

Starts Then Dies Subaru WR-X

It can be very disconcerting if your Subaru WRX is starting and then dies.  It is most likely caused by some type of issue with the electrical or fuel system.  But, there can be other causes as well.

Your WRX’s engine needs 3 things constantly and in the proper proportion to keep running.

  • Air
  • Fuel
  • Spark

If you vehicle starts up, but then immediately quits, it may be getting all three at first, but something is clearly keeping it from getting all three consistently.

When you turn the key to the on position, all three of these system engage and are ready for you to start your WRX.  Once you hit the starter it turns the engine slowly.  As soon as the engine gets enough fuel, air, and spark it runs on its own.

At this point the starter is disengaged and the vehicle will need a constant supply of gasoline.  If there is not enough fuel pressure to meet the needs of the vehicle, the engine will shut down.  This is one of the most common reasons why a car starts and then dies.

Modern vehicles have complex computer systems that can tell you the reason that the vehicle is dying immediately after starting it.  We recommend looking to see if there are any OBD2 codes before proceeding with any manual diagnosis.

 

Causes:  WRX Dies After Starting

Here are some of the most common reasons that your WRX starts then stops running:

 

1. Lack of Fuel Pressure

WRX Fires Up then Dies

Modern fuel injected engines need a lot of fuel pressure to keep running.  When they don’t have the proper pressure, they can’t run properly.  There are a few reasons that you may not have enough fuel pressure.

There could be a bad fuel pump.  The fuel pump may be providing enough fuel pressure when starting the engine, but not providing enough to keep it running. 

The fuel pump is found in the gas tank.  But, most engine’s have a port that will allow you to check the fuel pressure with a gauge that you can rent or buy from a store such as Autozone.  Take note of the fuel pressure as you turn the key to the on position.  Now start the engine. 

Does the fuel pressure drop almost immediately?  Does it go all the way to zero?  If it drops all the way to 0 and doesn’t come back, it’s most likely the fuel pump relay.  If it drops lower, the engine dies, but then the fuel pressure bounces back, it’s most likely a bad fuel pump or fuel filter.

An experienced mechanic with a good scanner can check the voltage at the fuel pump relay to determine if it is getting constant voltage.

 

2. Lack of Spark

Most modern vehicles are powered by individual coil packs.  But, some older engines aren’t.  If you have a coil on distributor engine, a bad coil can start a car, but might not have enough spark to keep it running. 

 

3. MAF Sensor

Typical MAF Sensor Location

The mass airflow or “MAF” sensor meters the amount of air entering your WRX’s engine.  It sits in between the air filter and the throttle body.  It is one of the most important components that the vehicle uses to determine the air/fuel mixture.

If it is not properly giving a proper reading, it is known to make the car not start.  Take a look at the wiring harness around it and make sure that it is plugged in good and tight.  Follow the wiring as far as you can and make sure that it is not burnt, frayed, or in any other way damaged.  Here’s a in depth article on how to diagnose a bad mass airflow sensor.  If you do end up cleaning it, make sure that you get a cleaner specifically designed to clean the sensor and nothing else.

 

4. Ignition Issue

Subaru WRX Dies After Starting Dash Lights Off

When you start your WRX, it may be that the vehicle’s systems are only coming on when you hit the starter.  This is a condition that happens when the ignition lock has worn out.

Basically, the vehicle is only being told to “be on” when the starter is engaged, and all systems are going off when releasing the key.  There are a few things you can do to tell if this is the issue with your car.

Try starting it with a different key if you happen to have one.  A newer key in an older ignition may be enough to trigger the “on” circuit and keep the vehicle running.

If you don’t have another key, take a look at the warning lights on the dash.  If they come on when you put the key into the on position, it probably means that this is not the issue.  If they are only coming on right as you start the vehicle, that could mean that you need a new ignition switch. 

Do not trust the radio, window, or power seats to tell if the vehicle is on.  They are often on a different circuit.

 

Diagnosis

The first thing that you would want to do is hook up a good code scanner and see if there are any trouble codes present.  These can really help illuminate what is going on with the vehicle. 

If nothing is found, the causes listed above are some of the most common reasons.  Otherwise taking it into a good shop might be what is best.  A vehicle that stops right after starting can be difficult to diagnose.

Good luck fixing your WRX.  If there is anything that you would like to add that could help the next person, please leave a comment below.

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