Fuel Injector Leaking Into Cylinder: Symptoms, Reasons, and Fixes

When something is leaking inside your engine, it doesn’t promise you anything good. Leaking fuel can change the way the engine works, dilute the oil, affect the work of a certain cylinder, and also lead to fatal engine failure. So, in this article, I want to tell you more about the symptoms and possible fixes of the fuel injectors leaking into cylinders.

In short, fuel injectors may leak into cylinders because they are clogged or broken, you should repair this problem as soon as you identify it because this can lead to engine damage. The leaking oil may cause engine misfiring, poor gas mileage, low power, and engine codes triggering the check engine light.

Here’s what I’m going to cover in this article:

• What are the common symptoms of leaking fuel injectors?
• The reasons why your injectors may leak into cylinders.
• What should you do if you encounter this problem?
• Can you still drive when one of the injectors is leaking?

How can you identify that injectors are leaking into cylinders?

Identifying this problem is not that easy. There is no clear symptom that this is happening and you should gather all the symptoms to see the actual problem. Sometimes, even experienced mechanics spend quite a lot of time before they recognize this issue. The explanation is pretty simple – it doesn’t happen that often in modern cars.

Let’s see some basics first. The fuel should be atomized properly in order to form the air-fuel mixture. If it’s just sprinkled into the cylinder or some drops are leaking randomly, the process of combustion will be changed. This will affect the work of the engine and will certainly make it less efficient.

Here are some of the common symptoms of injectors leaking into cylinders:

• you can clearly smell gas when you open the hood, the smell is quite sharp;
• the engine is working harshly, it vibrates and nearly stalls at times, the RPM is not stable when the engine is idling;
• your car has lost power – it seems to be using one cylinder less than usual;
• you can see the check engine light and the code will most likely tell you about the misfire in one of the cylinders;
• also, some other codes may be there – catalytic converter, oxygen sensor, fuel supply problems, etc.;
• the engine may knock – this usually happens when the excessive fuel detonates or explodes inside the engine;
• also, you may find it harder than usual to start the engine.

These are the standard symptoms of a leaking fuel injector. They may come in different combinations and be more or less recognizable. I also know cases when heavily leaking injectors remain unnoticed in V6 and V8 engines for a long time because all these symptoms are soft or mild and don’t affect the overall performance of the engine that seriously.

So, it’s important to react even if the symptoms of the leaking injectors don’t affect the engine heavily and you can still drive it. It doesn’t mean that the problem is minor and may be overlooked. It shouldn’t because it may lead to fatal engine failure even when it doesn’t show bad symptoms.

What are the reasons for fuel injectors leaking into cylinders?

I read some articles online before I started writing this article and they were completely misleading. Like they all said the O-ring in the injector rail can cause this leak. But no, it can’t because it actually holds the injector in place and isn’t connected to the injection process. So, be careful when you rely on information from unverified sources.

I can think of these reasons for fuel injectors leaking into cylinders:

1. Clogged or dirty injector. Usually, injectors atomize the fuel. But if they get clogged, they can just sprinkle the fuel and it won’t burn completely in the process of combustion. Clogged injectors can be cleaned or replaced depending on how badly they are affected.
2. Broken fuel injectors. I will not focus on what exactly can brake inside the injectors because it doesn’t make sense. If your injector is leaking because it’s broken, cracked, misshaped, etc., it should be replaced as soon as possible.
3. Injectors not holding pressure. In modern vehicles, the pressure of fuel is insane, especially in direct injection engines. It means that once something is wrong with the injector, it will leak fuel not only when needed, but at all times.

I believe these are the three most common reasons. Also, in very rare cases, the pressure of the fuel in the system can be higher than normal and this can affect the injectors. This may happen when you install the non-appropriate pump or make some other changes and upgrades in the fuel supply system.

But, in 99% of cases, those three reasons will be worth checking first. They are most likely the culprits of your problem.

Can you change injectors between cylinders to check them?

This is a very common question people ask, so I decided to answer it right away to avoid questions in the comments.

Here’s the answer: you can’t change injectors between cylinders like spark plugs or coils, for example, to check which one is malfunctioning. In modern engines, fuel injectors have their own individual codes and they are coded in the ECU. If you change the cylinder 1 and cylinder 2 fuel injectors, they may not work well.

This is not applicable to all engines, but modern powerplants will certainly not allow you to swap injectors between different cylinders. Avoid doing this if you aren’t sure that it’s OK for your engine!

Also, after you install the new injector, you will need to program it in the ECU with the help of a good scanner. Again, not all engines need this, but some modern units will not show full efficiency without this procedure.

What can happen with the engine if one of the injectors is leaking?

Unfortunately, the consequences of a leaking injector may be very bad. If not addressed timely, this problem can even lead to the death of the engine.

Here are the most important consequences:

• the fuel will not burn completely and will get into the catalytic converter where it will explode because of the high temperature;
• the catalytic converter will be destroyed pretty fast and it’s not the best news for you because its price is pretty high;
• the car will be backfiring and burning everything in your exhaust system, and some of those pieces of equipment are very expensive to repair or replace;
• some part of the fuel will wash the oil film from the cylinder after leaking down;
• this will lower the compression and make the misfiring effect even worse than it was before;
• also, the fuel will get into the oil pan and will dilute the oil bringing the death of your engine closer;
• diluted oil will lose its efficiency and will not lubricate the engine.

As you see, the problem appears to be much worse than it seemed to be at first. And while you may have been thinking that you can drive several hundred miles with the leaking injector before you go to the repair shop, now you may change your mind. Actually, you can drive with this problem, but you better plan your route to the nearest dealership or repair shop to have the car inspected and repaired.

Even if the misfire problem will not be connected to the leaking injector, you better check it before making any other decisions.

How to solve the problem with the leaking injector?

If one of your injectors doesn’t hold the pressure or is broken, there is only one way to solve the issue – to replace the injector with the new one. I always recommend only OEM injectors, aftermarket ones are not long-lasting and can fail at any moment.

If the injector is clogged, you may have it cleaned. There is no good and efficient DIY method to clean the injector in your vehicle. Professionals usually use cleaning equipment that is attached to the injector and the unit is cleaned with different chemicals using mechanical methods.

I can feel you are about to ask if you can clean the injectors with the injector cleaning additive that you can buy in car part stores. My answer is NO, you can’t clean your injector with these crappy additives and you shouldn’t even try.

Here’s how to actually solve the problem:

• use the OBD2 scanner and see the code – it may tell you which cylinder misfires and you will be able to locate the problematic injector;
• take the injector out and see if it’s damaged, cracked, or something like that;
• have this injector cleaned in the professional repair shop and see if this helps (after that, you should clean all injectors);
• replace this injector with a new one and see if it helps – you may buy a cheap aftermarket alternative just to check the idea;
• or better go to the repair shop and have your injectors inspected thoroughly.

I would immediately go to professionals because problems with leaking injectors are really dangerous for your engine. You never know how many miles you have till the disaster happens.

Final thoughts

Well, the leaking injector may not seem like the worst problem with your car. But it’s obviously not the issue you should ignore. If you do, the consequences may be disastrous.

You can’t recognize leaking injectors easily, so it’s always a set of factors that you should pay attention to. But now, after reading this article, you are ready to react quickly and easily to such problems.

If you still have any questions, just ask them in the comments below.