How to Check For Leaking Fuel Injector and Fixes

The fuel injection system is a vital component responsible for spraying the right amount of fuel into your cylinder walls, helping to complete the combustion process. When your fuel injectors go bad or start leaking, it affects the engine’s performance and develops several leaking fuel injector symptoms.

Symptoms like reduced gas mileage, white smoke, misfiring, poor emission, erratic engine idling, and in a bad scenario, engine knocking. However, an external fuel injector leak will cause a fire outbreak if not noticed on time. Who would want his car to get burnt?

Read on to learn how to check for leaking fuel injectors to ensure your engine runs optimally and prevent fire outbreaks from external injector leaks and vacuum leaks.

How to Check for Leaking Fuel Injector

When you have an external leaking fuel injector, the common thing that indicates is ‘ gas smell comes within your car’. Here’s an essential guide on the fuel injector leak test.

new fuel injectors leaking

What will be the outcome of a leaky fuel injector? For instance, your no. three and four fuel injectors are leaking while one and two are okay. What will happen is that no three and four injectors will spray excess fuel into the cylinder. The computer will send a message to the ECM to reduce the amount of fuel the fuel injectors are spraying.

The ECM will not know exactly the injector that is spraying excess fuel, so the ECM will reduce the fuel that all the injectors are spraying. Since the ECM has reduced the right amount of fuel that the non-leaking injectors are spraying, it’ll result in inadequate fuel flow from no one and two cylinders.

When this happens, Your computer will store a misfire code in the system. P0301 cylinder 1, p0302 cylinder 2, p0303 cylinder 3, p0304 cylinder 4 codes. Once the computer adjusts the spraying rate of non-leaking injectors, it will be translated to a misfire. There could be sorts of variations from this point. However, it is important to know how your injectors work and how they will affect your engine.

That said, let’s dive straight into step-by-step guides.

Step 1: Start your engine, while it’s running on idle, inspect the fuel injectors individually for leaks. If there are any external leaks, your fuel injector O ring is possibly the cause. If this is the case, you’ve to get a new o ring and replace the damaged ones.

Step 2: Turn off your car engine and remove your battery negative terminal. Remove your air filter box from the way (if it’s blocking you) by unscrewing the fasteners holding it.

Step 3: Depending on your car model, disconnect your throttle cable or unplug your throttle socket. Ensure you gently remove all the wires along the way.

Step 4: Disconnect the socket on your injectors. Unbolt the fuel rail and gently pull off the rail with injector remover. To properly do this test, you have to ensure you leave the fuel lines on the fuel rail to deliver adequate fuel pressure from the fuel pump.

Step 5: get something to measure the fuel’s pressure, something like a syringe that has milliliters.

Step 6: Take your multimeter and test the voltage on your injector sockets. On most cars, injectors have two pins. Numbers from 3.70 and 3.89 are okay. You don’t want to see any variations above that.

Step 7: Remove your fuel fuse and take a close look at it; you will see PIN 87 and 30, which are the main fuel lines(these numbers may differ from cars to cars). Contact the fuse to keep the fuel running steady.

Step 8: Send current to your injector and examine the spraying rate of your injectors individually. the reason I asked you to use something like a syringe with milliliters numbering on the body is to determine the level of fuel entering into the container during this process. You can decide to allow the fuel to get to 30-50 milliliters, the higher it is, the more accurate it is likely to be.

Step 9: In this testing model, it is ideal to record the time that all the injectors take to fill the milliliter container. If you can’t get a milliliter container to carry out this test, you can use any other container. However, you’ll have to watch the spraying rate close. The spraying should be running smoothly. You should not see big drops coming out. Once you notice any injector that is spraying excess fuel, it is an indication that the said injector is leaking. For a clear visual presentation, watch this video.=

How To Fix Leaking Fuel Injector

Just like checking for fuel-leaking injectors, you have to clearly look at the injector areas to see if there is any leak. A wet injector area is a clear indication that your injectors are leaking externally.

First thing first, after inspecting your injectors for external leaks, disconnect your battery to avoid spark. With your correct toolsets handy, Get your air box out of the way by taking off the screws holding it.

Loosen the bolts holding your throttle body, unplug the socket or throttle cable, depending on your car model, take off the water, and air hose connecting to it. Carefully unplug all the sockets and wires along the way. Look at the surrounding areas and ensure you remove anything blocking your way. Gently Unplug the injector sockets to avoid breaking the fitting pins.

Take your underhood work light and inspect your injectors for any external leaks. Any fuel around your injector areas is likely caused by a leaking fuel injector o ring.

Loosen the bolts holding the fuel rail, gently pull it off, and inspect the o rings individually. If the o ring has any impact on it, you have to get new o rings and replace the damaged ones. You can replace all the o rings at once if you have original o rings that will stand the test of time. Broken o rings can cause air leaks from the injectors, which will affect your engine functionalities.

Follow the step-by-step guides above to check for internal fuel injector leaks– once you find any leaking injector, get a new one and replace it. Fuel injectors are relatively affordable, though the actual leaking fuel injector repair cost varies. Depending on your car model and make, with $600 to $1,250, you’ll get your leaking fuel injector fixed. The cost of getting a new fuel injector will be $400 to $900 and the service fees will be around $200 to $250.

injector seals leaking oil


Can I drive with a leaking injector?

If your car is having internal leaks, you can drive it for a few miles. This doesn’t mean that your car will not move, it’ll take you around. But it will deeply affect the efficiency of your engine. If you experience external leaks, cautiously find a safe place and park your car. If you continue driving your car with external fuel injector leaks, it’ll cause a fire outbreak in no time.

Can you fix a leaking fuel injector?

Yes, you can easily fix a leaking fuel injector. If your injector has an internal leak, your best bet is to get a new injector and replace it. If it happens to be external leaks, or you have a fuel injector leaking air, it is most likely caused by weak or broken o rings. If a thorough diagnosis proves the cause to be o ring, you can easily replace the o ring and get your car running again.

When should I replace my fuel injector O ring?

Without minding how small your fuel injector O rings are, they play a vital role in your car engine performance. When your fuel injector O rings go bad, it will not only affect your engine performance, it will also cause fuel odor around your car, which might cause a fire outbreak if not noticed and fixed on time.

Once you see any of these noticeable symptoms, It is an indication that your fuel injector O rings need to be replaced:

  • Fuel odor within your car
  • Wet fuel injector areas
  • Impact on the fuel injector O rings.

How do you do a fuel injector leak-down test?

Carrying a fuel injector leak-down test is quite a simple task. This method is suitable for car engines that have port Schrader valves. The easiest way to carry out this process is by installing a performance fuel system EFI gauge kit.

Install the EFI gauge kit, start your car engine and allow it to idle. Check for fuel leaking injector for 20 – 45 minutes. Ensure you observe the fuel pressure closely. The pressure should be between 35-50 psi. Turn off the engine and watch the drop in fuel pressure. A 2psi per second is a swift drop down and indicates a fault. A much slower speed is very okay.

Final words

As you have seen, leaking fuel injectors can cause fire hazards and severe engine problems. Ensure you fix fuel leaks immediately after you notice them to prevent damage to your car engine.

We have successfully walked you through how to check for the leaking fuel injector and ways to get them fixed. Feel free to drop any questions and/or comments in the comment box.

Read More:

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Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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