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The following guide will discuss the three most common reasons why a Porsche won't start.

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A lot of joy can come from owning a Porsche. They can bring quality, performance, and luxury into your daily life. For almost 100 years, the brand has been praised globally for its reliability, with over 70% of all 911s ever built still being on the road today. But what happens on that enviable morning when you're running late for work and your beloved 911, Panamera or Cayenne won’t start?

It doesn't matter what brand of car you choose to ferry you back and forth to the office every day. One day you will get in, turn the key, and nothing will happen. In this article, you will learn about common issues that can cause your Porsche of any vintage not to start and inform you of a few tips that can get you back on the road sooner.

Dead Battery 

porsche dead battery causes no start problem

Let’s start off with a basic problem: the battery. From the original Porsche 901 to the brand new 992, they all have an external battery to give base power to the vehicle's system to get it up and to run. In classic cars, the battery’s main purpose is to send power to the starter motor and fuel pump when the ignition is turned on. After the engine turns over, the alternator takes over the electrical production and sends extra voltage back to the battery to keep it topped up. If the ignition was turned off, no voltage was sent to any accessories. This made it so it wouldn't constantly pull power from the battery, causing it to die.

In modern cars, the principle is still the same but with tons of other systems added on top of the basic fuel and ignition. Cars today have hundreds of computer modules. Each is charged with monitoring every aspect of the vehicle, and each draws power from the battery, some even with the ignition turned off. The Porsches of today have various monitoring systems in the doors and cabin that continue to run after the car has been shut down.

In ideal conditions, after a short time, the modules go to “sleep” and completely shut off. Faults in the system, such as lights left on or the doors not being closed properly, can cause the car not to sleep. This leaves the systems running and the battery on the hook for the juice, causing the battery to die.

This can happen to anyone, so the good idea is to buy a portable jump pack to keep in your car at all times. This portable AAA personnel is around $150 and is only a little bigger than your cell phone. A jump box is a superior option to traditional jumper cables as you no longer need the assistance of a good passing samaritan. In most modern cars, the battery is inaccessible under the floor in the trunk or the cabin, but jump posts are still located under the hood marked with a red + cover and an unpainted ground point. 

Starter Failure  

starter problem porsche won't start

Now that you know what could be wrong with the battery let’s move on to the next weak link in getting your Porsche to turn over: the starter motor. In order to get the engine going, a physical rotation of the flywheel has to take place; that's where the starter comes in. Mounted on the engine case, the electric motor has a small gear with teeth that mesh with the flywheel. When power is sent to the starter from the ignition, the gear spins giving the engine the initial shove that it needs to get running. 

Starter motors are worn items that only have a certain lifespan. Coupling that with a weak battery causes the starter to have to work harder than it should and it can shorten that lifespan.  Failure symptoms normally include a loud click sound after turning the ignition followed by nothing happening.

If your Porsche has a manual transmission, you can still get the car running by roll starting it. This involves the help of other people because you need a push to get the car rolling at a few miles an hour with you behind the wheel. If you're lucky enough to have assistance, here are the steps.

  • Get the car rolling in 1st gear with the clutch pedal depressed and the ignition on.
  • When up to a decent speed quickly release the clutch pedal.
  • If you were going fast enough and your battery has enough power the car should try to start.

This basically bypasses the starter motor and forces the engine to rotate. Applying a little throttle as you pop the clutch can help get the engine breathing but it might take a few attempts, so don't get discouraged if it doesn't work on your first try.

If your Porsche has an automatic transmission, like almost all cars built today, you're kind of out of luck here. The way the transmission is designed will not allow you to start the car this way and can seriously damage it if you try. So if the starter fails your only option is to tow the vehicle to reputable Porsche specialists and have it replaced.

 Ignition Anti-Theft Immobilizer

porsche won't start bad key

Porsches are nice cars. That is probably why you bought one and it is also the reason people steal them. In order to prevent this over the years, the engineers in Stuttgart have employed all types of anti-theft features but around the 90’s they discovered ignition immobilizers.

How it works is the key has a microchip inside that is read by a computer when inserted into the ignition cylinder. If the module reads the proper code for that vehicle, power is sent to the starter motor and the engine turns over. However, if it doesn't read the key or the wrong code is displayed no power is sent and the car doesn't start. Normally this is caused by the internal battery in the key dying. They usually take flat watch-style batteries that can be bought almost anywhere. All you need to do is remove the back panel on the key and match the number on the back.

Water incursion is another hazard for the immobilizer like all electronics and can be a serious problem to any car. If you own a  911(996) or Boxster(986), this is a notorious issue because the immobilizer is located under the driver’s seat. As soft tops and door seals age water inevitably finds a way in pooling on the cabin floor. This soaks the module, frying it and not allowing the system to read the key. No key, no start.

Final Thoughts

Diagnose a porsche that won't start

These have been just a few examples of common no-start issues on Porsches. In the olden days of auto repair, you only needed five things for your car to run: fuel, air, spark, compression, and timing. Today things have changed and now you have to make 30 computers happy before the door will open but the core concepts remain the same. Nine times out of 10 if your Porsche won’t start it’s electrical-related, that is if your fuel gauge works.

If your Porsche won't start, consider getting a Porsche Scanner and read the codes from all the modules. You will get a number of fault codes but pay attention to those codes that have a PRESENT or CURRENT state. Those codes will usually direct you on the correct path to troubleshooting a Porsche that won't start.