Why Won’t My Lexus RX 350 Start?

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The Lexus RX 350 is a mid-size luxury SUV that’s great for transporting people, cargo, or both. It’s designed to be strong and tough enough to withstand any weather, so you can take it off-roading or through the snow without worrying about damage.

The RX 350 is, without any doubt, an amazing SUV. It is powerful, luxurious, and practical as well. But many owners had to find out the hard way that it is not perfect.

Some have often wondered, “Why won’t my Lexus RX 350 start?”. The answer can be divided into several parts. Let’s take a look!

  1. Weak Or Dead Battery
  2. Frayed Battery Cables
  3. Faulty Spark Plugs
  4. Clogged Fuel Filter
  5. Complete Engine Failure

As you may see, some of the reasons given in the list above are concerned. The bright side of this is that I will be discussing them with you in detail, so you can know more about them.

What Would Cause A Lexus RX 350 To Not Start?

Why is your Lexus RX 350 not starting? Learn why from my guide

The introduction stated some reasons that could be preventing your Lexus RX 350’s engine from turning over.

They were listed in the order of likeliness of occurrence, so I will discuss them in the same manner with you.

1: Weak Or Dead Battery

A weak or dead battery is one of the most common causes of a Lexus RX 350’s engine being unable to turn over.

This can happen if you’ve left lights on or used any electronics while your vehicle was turned off and the alternator was not being used.

If your SUV has been sitting for a while, the battery may have lost some of its charge. It could also be that the battery on your RX350 is completely dead.

This is to be expected after its expected lifespan, which is around 4 to 5 years. You may experience symptoms of this eventual failure in the battery’s last few weeks.

Some of the common ones are:

  • Difficulty starting
  • Slow accessories
  • Dim lights

What Should You Do About It?

  • If your Lexus RX 350 is starting to lose power, you may need to replace the battery. There are two steps to follow if this is the case.
  • Try charging your battery. You can use a trickle charger or jump-start the engine, so the alternator can do it for you.
  • If that does not work, then it means the battery is dead. There is no way to get a dead battery to accept a charge.
  • Replace the battery with an AGM battery from a brand like Optima.
  • These batteries are designed for heavy-duty environments and offer superior performance over traditional lead-acid batteries.
  • Lastly, they don’t need any maintenance. The investment in an AGM battery is worth it.

2: Frayed Battery Cables

Your Lexus RX 350 can cause you starting problems if your battery cables are frayed.

The cables connect your SUV’s starter to the battery and send electricity to the starter when you turn the key.

They can’t send enough power to start the engine if they’re torn or worn. If the cables are frayed, jump-starting will not help either.

The reason is that there is no proper connection with the vehicle’s electrical system to send the current. You can easily check if your battery cables are frayed.

Pop open the hood of your RX 350 and observe the wires connected to the battery’s terminals. If silver wires are poking out, then you have your answer.

What Should You Do About It?

  • If you’re experiencing a problem with frayed battery cables on your SUV, there is only one thing you can do, replace them.
  • First, you should replace them with wires of the same gauge or thicker.
  • If you go with thinner ones, you risk those wires melting and causing an electrical fire.
  • This is something you do not want. It is better to spend a few more dollars than see thousands of dollars worth of damages.
  • Second, make sure to get the best quality cables possible.
  • The better quality wire you use, the less likely it will be to fray and cause problems for your Lexus RX 350 in the long run, as it is more heat resistant and less prone to wear.

3: Faulty Spark Plugs

If your Lexus RX 350 doesn’t power up, it could be that your spark plugs are faulty.

Spark plugs ignite the fuel inside the engine and provide the necessary power for your vehicle to run smoothly and efficiently.

A bad set of spark plugs will cause a misfire in your engine, leading to other issues such as poor gas mileage, rough idling, and even loss of power when accelerating.

A common symptom of faulty spark plugs is a cranking sound produced when trying to turn the key in the ignition.

Now, this sound can be a result of the failure of some other part, but it is more likely to be the plugs.

What Should You Do About It?

  • The first thing to do is replace all of them at once.
  • If one of the spark plugs has failed, there’s a good chance that others will fail soon, too—so it’s best to replace them all at once.
  • Mismatching hardware can also lead to issues with the engine. You should also make sure you use the same quality spark plugs across the board.
  • If possible, don’t settle for anything less than iridium or platinum spark plugs.
  • These high-quality plugs will last longer and perform better than cheaper alternatives, such as copper or silver.
  • As a bonus, a set of spark plugs is cheaper than buying them individually. So, why wait for others to fail?

4: Clogged Fuel Filter

The fuel filter is located inside the gas tank and is responsible for filtering out particles that could cause problems in your engine.

If your Lexus RX350 is having starting issues, especially after getting gas, then there is a very likely chance that the filter is clogged.

Just like with faulty spark plugs, a clogged fuel filter can result in the engine producing that distinct cranking sound.

The cranking sound is produced when the combustion process cannot take place properly. As the filter is not letting fuel through, this symptom is observed.

Fortunately, you don’t have much to worry about if the issue is just a clogged filter. Read below on how to alleviate the issue.

What Should You Do About It?

  • Although some suggest cleaning the fuel filter instead of replacing it (usually not recommended), this will only temporarily fix the problem while allowing more dirt into your engine.
  • The dirt will wreak havoc on the moving parts, resulting in much quicker wear and tear.
  • The best way to fix a clogged fuel filter is by replacing it with a new one. A new filter is not too expensive.
  • You can buy one from any local hardware store. But you should make sure to avoid the cheaper options.
  • The filter is not as fine as others, which can lead to some contaminants entering the engine.

5: Complete Engine Failure

The last option on my list is the least likely to happen, but it’s still possible. If you’re having trouble starting your Lexus RX350, it could be a matter of complete engine failure.

An engine failure can be due to negligence or extreme wear and tear. This can lead to pistons breaking, which can, in turn, damage the engine even more.

If this happens, then repairing specific parts can be difficult to impossible. Read below to see your options if you are unlucky enough to experience an engine failure.

What Should You Do About It?

  • When you have a complete engine failure, the best thing to do is to decide whether to rebuild or replace it.
  • Rebuilding is cheaper but will not be as good as getting a new engine.
  • All parts replaced in a rebuilt engine will be used from other SUVs, which means they may not be perfect and may not last as long.
  • Replacing an engine with all-new parts will ensure that your Lexus RX 350 runs like new, and you won’t have to worry about any issues in the future.
  • Plus, the engine will run for the advertised mileage, which means you will have breathed new life into your RX 350.
  • Both of these solutions, in general, will be pretty expensive. I would recommend going for a complete replacement.

Frequently Asked Questions

Q1. Why Won’t My Lexus RX 350 Start With New Battery?

You probably just need to charge your new battery.

Make sure you’re using a trickle charger and not just relying on the SUV’s alternator, which can take several days to fully charge your battery.

A charger will do the same job in a few hours. It is better to leave the battery charging overnight.

Q2. Why Won’t My Lexus RX 350 Start Even With A Jump?

Check your cables and clean the terminals if necessary, but if still jumpstart doesn’t work, you may need a new battery.

It could be a frayed battery cable or corrosion on the terminals. It is better to look out for the symptoms than blindly try solutions to see which one will work.

Q3. Why Won’t My Lexus RX 350 Start But Lights Work?

Your battery may be alright—you might have an issue with the starter motor or ignition system. Check those first before you replace anything else! Both of them are not too expensive.

A starter or ignition system may also not work due to blown fuses. Make sure to check them out too.

Q4. Why Won’t My Lexus RX 350 Start But Cranks?

If the engine is cranking, the spark plugs or the fuel pump prevent the engine from turning over.

You need to check both of them and ensure that the faulty part is replaced as soon as possible. In the fuel pump case, make sure to get the exact model number.

Q5. Why Won’t My Lexus RX 350 Start Just Clicks?

The most likely cause of this problem is a bad starter motor. You may have to replace it, costing you around $200.

If the starter motor is fine, the problem could be due to a faulty ignition switch or another electrical issue. They can result in a clicking sound being produced.

Q6. Why Won’t My Lexus RX 350 Start In The Cold Weather?

If your Lexus RX 350’s engine doesn’t turn over in cold weather, the battery may have too few Cold Cranking Amps (CCA) to provide enough power for the engine to turn over.

Your battery should have at least 800 CCA to start the engine in cold weather. You can easily buy one that fits this description.

Q7. Why Won’t My Lexus RX 350 Start After I Get Gas?

If you fill up with gas and then your vehicle refuses to get going, it could be because the fuel pump isn’t working properly or because there’s something wrong with the fuel filter on your Lexus RX 350.

To fix this issue, take your vehicle to an auto repair shop and get both checked. You may need to replace one or the other to get your SUV working again.

Q8. Why Won’t My Lexus RX 350 Start But Radio Works?

The battery may be low on charge. This can happen if you left the lights on overnight or used the radio a lot while the Lexus RX 350 was off.

A battery with a low charge will not be able to start the engine. If this is the case, your radio should still work because it draws very little power from the battery.

You will need to use a charger.

Related: What Are The Worst Years For The Lexus RX 350?


If you’re having trouble getting your Lexus RX 350 to start, don’t worry! It might just be a simple fix.

It could either be the battery or the spark plugs. It could also be something much more serious. But let’s not jump to conclusion.

If you cannot identify the symptoms of what is causing starting problems, it is never a bad decision to visit an auto professional.

You could also simply call a friend with more experience in this area than you do.

Regardless, if you read this article completely, you certainly won’t be asking the question, “Why won’t my Lexus RX350 start?” again.

I hope you can get your SUV up and running in no time.