Lexus IS250 Won't Start but Has Power - What's Wrong?

If your Lexus IS250 won't start but has power, it could be one of many reasons. A few common culprits are a dead battery, faulty starter, fuel system problems, or ignition system failure.

No-start problems highlights

• Level of urgency:High
• Can you drive?Obviously, no
• DIY inspection:Possible but complicated
• DIY repair:Mostly,impossible
• Price for repair:$250 - $850
• Common Reasons:Fuel or air supply, compression, spark, electronics
• Ways to fix:Check each system that may cause no-start, check electronics

Dead Battery

If your Lexus IS250 won't start but has power, one of the common causes is a dead or weak battery. The starter motor which fires up the engine is powered by the battery. If your Lexus IS250 battery is dead or weak, it won't be able to power the starter motor. If the battery is weak, despite being able to power a few other electronics in your car, it just might not have enough juice to turn over your engine. 

There are several causes that can lead to draining your battery. One such mishap that happens to everyone is keeping the headlights or any other electronic accessories on even if your engine is not running. This can drain your battery's charge rendering it unable to start your car. Another potential cause that can drain your battery is a faulty charging system.

Your battery recharges as your car runs. This is done by a unit called the alternator which is responsible for recharging the battery while the engine is running. If your alternator is malfunctioning, without a way to recharge, it is just a matter of time before your battery dies. 

Diagnosis

Diagnosing a weak battery is quite simple as it powers numerous components in your car. Start by checking if the lights, radio, and other electrical components are functioning properly. If your battery is weak, it might still be able to power some of these accessories, so switch them all on at the same time.

If they are weak or not working at all, it is a strong indication that the battery is discharged. Even with everything on, if all your electrical accessories are working fine, the problem might not be with the battery and you should continue your search.

Solution

If the battery is the issue, a temporary solution would be to jump-start your battery. This can be done using a portable jump starter kit or with the help of a charged battery from another car and some jumper cables. This jolt of power will be enough to start your engine and get your battery recharged. 

Even though your car might run again after jump-starting the battery, your job is not done. You should dig deeper and find the exact reason why your battery drained in the first place.

For example, if the problem was caused by a malfunctioning alternator, it's only a matter of time before your battery drains again. So, you need to run a proper diagnosis on the battery's health, charging system output, and identify any potential faults.

Faulty Starter

The starter motor is what starts the entire Lexus IS250. When you insert your key into the ignition and turn it over, a circuit is completed and an electrical signal is sent to your starter motor.

Even if you have a newer model that doesn't involve a mechanical key, an electrical signal is sent to the starter motor in the same manner when you start your car. 

When the starter motor receives the electrical signal, it engages a small called the pinion gear. The pinion gear meshes with the flywheel, which is a large gear attached to the engine. The rotation of the flywheel cranks the engine initiating combustion. Now that you know the role of the starter motor, it's not hard to imagine why your Lexus IS250 won't start despite it having power if you have a faulty starter. 

Diagnosis

There are several signs that'll allow you to accurately diagnose a failing starter motor. One of the more prominent signs is the clicking sound when you turn the ignition key. The clicking noise is a result of the starter motor itself not engaging properly, even though the starter solenoid is getting power. 

Another symptom of a failing starter motor is grinding noises when activating the starter motor. This happens as the pinion gear and flywheel haven't meshed properly, which causes the gears to grind against each other. 

Solution 

The only way to know whether repairing your starter motor is possible is to take it apart. If the problem is down to bad solenoid valves within the starter motor, repairing it will be an option. But more often than not, when your starter motor fails, you'll have to get it replaced.

Another unorthodox and temporary solution that is known to work is gently tapping the starter motor with a hammer. Though it is not a guarantee, it's worth a try. Sometimes, that just might be enough to free up internal components of the starter motor and fire up your engine. 

Fuel System Issues

Even if your battery is fully charged and your starter motor is working just fine, if your engine is not getting fuel, it is not going to start. The fuel system in your IS250 is calibrated to supply your engine with an adequate amount of fuel when needed.

If your engine is not getting enough fuel or no fuel at all, it is not going to start when you turn the key, even though the rest of the ride might have power. 

There are many reasons why your engine might not be getting fuel. One common cause that is overlooked way too often is an empty fuel tank. There is no way your car is moving if your tank is empty. Check your fuel tank before pointing fingers when your Lexus IS250 won't start but has power. 

A clogged fuel filter can also cut off the supply of fuel to the engine. Over time, the fuel filter can accumulate dirt, debris, and contaminants, impeding the flow of fuel to the engine. This can simply be prevented by regular maintenance and replacing the fuel filters according to the manufacturer's recommendation. 

Diagnosis

Turn the key to the "ON" position, but don't start the engine just yet. While your Lexus IS250 is at an "ON" keep your ears cocked and listen for a faint humming noise coming from the fuel tank area.

Under normal circumstances, you'd hear a faint hum which is the sound of the fuel pump drawing fuel from the tank. If you don't hear this faint hum, it might be your fuel pump that is malfunctioning.

Solution

First off, make sure that your fuel tank is not empty. If it is empty or even running low, go ahead and fill it up. Then follow up by checking your fuel lines. If they are damaged or clogged, get them replaced as needed. While you are at it also check your fuel filter and replace it if needed. 

If you diagnose that your fuel pump is faulty, it is better to get an expert's opinion before doing anything else. Even if you have the skillset and the necessary tools to replace your fuel pump, it is a costly repair. In some cases, the fuel pump is repairable. So, before you take any rash decisions, it is best to weigh your options. 

Ignition System Failure

Finally, we should also look at ignition system failures which can also be the reason why your Lexus IS250 won't start but has power. The ignition system offers the final touch needed to fire up your engine.

Once your fuel system delivers the fuel to the ignition chamber, the ignition system is responsible for igniting the air and fuel mixture and finally starting your engine. Without the spark from the ignition system, your Lexus IS250 won't start despite having power. 

Several potential failures can occur within the ignition system. Usually, when the ignition system fails, it's due to the spark plugs. Over time, your spark plugs tend to wear or corrode. If this happens, the spark created by the ignition system will be weak or non-existent. 

Faulty ignition coils can also lead to ignition system failure. The ignition coils amplify the current from the battery before it reaches the spark plug. If the ignition coil fails, you might end up with a weak spark or no spark at all. 

Finally, the problem could also lie with the ignition switch. It can prevent the current from reaching the ignition system altogether. 

Diagnosis

In the case of an ignition system failure, the only way to diagnose the issue is through a visual inspection. You'd have to inspect the spark plugs and ignition coils individually and look for signs of damage. 

Solution

Depending on what failed on your ignition system, the repair procedure will vary. In the case of spark plugs, carbon deposits, and rust can hinder operation. In such a scenario, you might be able to clean your spark plug and reuse it.

Otherwise, you'd have to get it replaced. The same procedure applies to the igniting coils and ignition switch. Replacing the necessary parts is the best course of action. Make sure to replace it with OEM parts or other high-quality parts that are approved by the manufacturer. 

Conclusion

If your Lexus IS250 won't start but has power, it can be due to any one of the above-mentioned reasons. Most of these problems can be avoided by proper maintenance, so make sure to properly maintain your Lexus IS250. And if you do run into any of the above-mentioned problems, you are now armed with the necessary information to tackle the issue.