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If you pop the hood of a car from the 1960s, 1970s, or 1980s, you’ll likely see a carburetor mounted on top of the engine. Before the rise of electronic fuel injection (EFI), carburetors were the standard method for mixing air and fuel and delivering it to the combustion chambers.
As automotive technology evolved, fuel injection systems replaced carburetors as the preferred choice. EFI systems include a fuel pump, fuel rails, oxygen sensors, and fuel injectors, all managed by an onboard computer that precisely controls how much fuel is injected into each cylinder. This advancement provides better fuel efficiency, consistent engine performance at varying altitudes, and reduced maintenance compared to carbureted engines.
While an EFI system relies on several components to function effectively, this article will focus specifically on the fuel injector—and the potential problems that can occur when it begins to fail.
The fuel injector is a component that controls the amount of fuel being delivered before combustion. These small parts connect to the fuel rail and either the engine block (or the intake manifold on some port-injected vehicles), and plug into a harness that communicates with the ECU.
While EFI systems are generally reliable, fuel injectors can still encounter problems. The spray nozzle at the end of the injector may become clogged with carbon deposits, preventing it from closing completely. The plastic electrical connection points are exposed to extreme temperatures and can become brittle, causing connectivity issues. In addition, the rubber seals inside the injector can dry out and crack over time, leading to external fuel leaks.
Failed or failing fuel injectors can cause a variety of issues.
1. Misfires
2. Rough Running
3. Sluggish Acceleration
4. Reduced Fuel Economy
5. Check Engine Light
6. Fuel Oder
In most cases, the symptoms of a failed injector are noticeable enough that you’ll have it repaired before major damage occurs. However, if a bad injector is ignored for too long, it can lead to serious and costly engine problems.
If a fuel injector fails in a way that causes it to continuously dump fuel into a cylinder, the engine can experience hydro locking. This happens when the combustion chamber — normally filled with vapor and gases — becomes flooded with liquid fuel. Because liquid cannot compress like air, this can result in a bent connecting rod, piston damage, or even total engine failure. Severe hydro lock damage often requires a complete engine rebuild or replacement.
When fuel mixes with engine oil, it reduces the oil’s ability to properly lubricate moving parts. Without sufficient lubrication, bearing damage can occur. If this happens, the engine will need to be disassembled and the damaged bearings replaced.
A faulty injector that continuously dumps excess fuel into the system can also damage the catalytic converter. Unburned fuel entering the converter can ignite inside it, generating extreme heat that melts or breaks down the internal components. Replacing a damaged catalytic converter can be very expensive.
If a failed injector floods the engine with unburned fuel, it can cause a no-start condition. Similar to hydro locking, this occurs when the cylinder fills with excess fuel before ignition, preventing the engine from turning over.
If you've started noticing signs of fuel injector failure while driving, don’t wait to address them. Although the risk of severe engine damage is relatively low, it’s still possible if the issue is ignored. More importantly, replacing a faulty fuel injector will restore fuel efficiency, engine power, and overall drivability, helping your vehicle run smoother and more reliably.
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