Fuel Injector Heat: Pressure Loss And Solutions

Fuel injectors are responsible for delivering fuel to the engine of your car, truck, or automobile. They inject fuel as a fine mist at a very precise angle into the intake manifold (or combustion chamber). Within the intake manifold, air and fuel mix, and the air-fuel mixture is then compressed in the combustion chamber. A spark plug then ignites the chemical reaction required to power the gasoline engine. A fuel injector that is not functioning properly can cause a host of issues, including reduced engine performance, poor gas mileage, rough idling, and engine misfires. One of the potential causes of fuel injector issues is heat and moisture damage, which can lead to cracks in the rubber seals or the injector itself. In some cases, a fuel injector may stop working after the engine warms up, which can cause the car to run on fewer cylinders.

Injector not pulsing when engine is hot

There could be several reasons why an injector is not pulsing when the engine is hot. Here are some possible causes and troubleshooting steps:

Common Causes

• Blown injector fuse — The injector fuse is generally found in the engine compartment's relay box. Fuses protect electrical circuits and components, including fuel injectors, from short circuits. A blown fuse will cause the injector to stop working, resulting in no injector pulse. Check the fuse by removing it from its socket and inspecting the internal wire for continuity. If the wire is cut, replace the fuse with a new one of the same value.
• Faulty injector power relay — The relay is usually located in the relay box in the engine compartment. If the relay is faulty, try swapping it with another one of the same value.
• Bad wiring harness — Inspect the wiring harness for any signs of damage or wear. Ensure that the connections are secure and that there is no corrosion or damage to the wires.
• Defective injector — If the above solutions do not work, the issue may lie with the injector itself. If there is no injector pulse on one cylinder, try unplugging the injectors one at a time to see if the engine starts. If the engine starts when a particular injector is unplugged, that injector is likely defective and needs to be replaced.

Additional Testing

• Measure injector resistance — Use an ohmmeter to measure the resistance between the two terminals of each injector. Compare the measured values to the maximum and minimum values specified in the injector datasheet. If the measured resistance is outside the permitted bounds, the injector may need to be replaced.
• Check for voltage — Turn the ignition key on and check for voltage on the injector. If there is no voltage, it could indicate a problem with the power supply to the injector or a faulty injector.
• Use a NOID light — A NOID light is a diagnostic tool that detects a digital signal from the ECU and flashes an LED light. If there is no LED flashing during cranking, it indicates that there are no pulses coming from the ECU.

Example Case

In a forum post, a user with a 1991 Eagle Talon TSI reported a similar issue. They observed that after the engine warmed up, shut down, and then restarted, the car would run on three cylinders. They checked the resistor pack and found that everything was at about 5.6 ohms. However, they noticed that there was no juice going to the injector when it was not working. The issue was resolved by replacing the injector.

Clogged injectors

Clogged fuel injectors can cause a range of issues with your vehicle's performance and should be cleaned every 30,000 miles. Unlike dirty injectors, which reduce fuel flow, clogged injectors completely prevent fuel from flowing through them. This can cause the engine to run very rough, and in some cases, the engine will not start at all.

Signs of Clogged Fuel Injectors

• Rough idling: Rough idling is a sign that your vehicle's engine is not getting enough gasoline. You will feel your vehicle vibrate as you sit at an idle, and you may hear the engine cutting in and out. If the clog is severe, your engine may stall.
• Dancing RPM needle: When your vehicle is idling, the RPM needle may bounce up and down. This indicates that your vehicle is getting spurts of too much air or too much gas.
• Engine misfires: Clogged fuel injectors can cause the engine to misfire, making the motor feel like it is sputtering and sending vibrations through the car.
• Poor fuel economy: Clogged fuel injectors can lead to a significant decrease in fuel economy. This is because the injectors may be leaking extra gas into the engine, which is then burned off.
• Engine won't start: In some cases, clogged fuel injectors can prevent the engine from starting altogether. This is because the injectors are unable to spray gasoline into the intake manifold or directly into the cylinders.

Causes of Clogged Fuel Injectors

Fuel injectors can become clogged due to hydrocarbons, sediment, and other elements in the fuel. Most fuels contain ethanol, which is hygroscopic and draws moisture from the air into the fuel. This water can cause internal components to rust, and the residue from this rust can clog the injectors. Additionally, smaller and older service stations may have debris and sediment in their storage tanks, which can eventually make its way into the injectors.

Cleaning Clogged Fuel Injectors

While there are over-the-counter fuel injector cleaners available, it is recommended to have them cleaned professionally. This ensures that all carbon deposits are removed and allows technicians to check for cracks and leaks. The only guaranteed way to properly unclog an injector is by removing it from the engine and sending it to a professional injector cleaning service.

Fuel leaks

Fuel injectors are responsible for delivering fuel to the engine of your car, and when they fail, the engine fails. Fuel leaks in the engine are dangerous and can cause a fire. Fuel injector leaks are generally caused by an O-ring failure between the injectors and fuel rails. Engine heat can make the O-rings brittle and cause them to crack, leading to a fuel injector leak.

There are several symptoms of leaking fuel injectors. Firstly, you may notice hard starting when the engine is hot. This is because the fuel rail pressure has dropped, and fuel has leaked into the manifold, causing the spark plugs to become flooded. Secondly, leaking fuel injectors can cause increased fuel consumption. This is because the fuel is being wasted through the leak and not being supplied to the engine. Thirdly, you may notice fuel odours inside and around the car. This is a strong indicator that fuel is leaking from the injectors. Lastly, leaking fuel injectors can cause oil thinning, which can lead to catastrophic engine failure and even an explosion inside the engine.

There are two types of fuel injectors: top feed and side feed. Top feed fuel injectors can leak at the top O-ring where the fuel injector is located in the fuel rail. This is repairable by replacing the O-ring. If the fuel injector body is leaking, the injector is not repairable and must be discarded. Side feed fuel injectors can leak at the top and bottom fuel injector O-rings, which is repairable by replacing the O-rings. If the fuel injector body at the top of the injector is leaking, the injector is not repairable and must be discarded.

If you suspect that your fuel injectors are leaking, it is important to take your vehicle to a trained technician as soon as possible. Do not drive your vehicle if you see any fuel leaks from the fuel injection components. Proper fuel injector cleaning techniques can restore your injectors to function like new at a fraction of the cost of new fuel injectors.

Dirty injectors

Dirty fuel injectors can cause a range of engine issues, from reduced fuel economy to poor overall performance. Fuel injectors are responsible for delivering a precise amount of fuel to your engine, and when they become dirty, they can no longer perform this function optimally.

One of the first symptoms of dirty fuel injectors is engine misfires. This happens when the fuel injector becomes clogged and cannot deliver the correct amount of fuel to the engine, resulting in incomplete combustion. The engine rhythm becomes uneven, leading to misfires, which are often felt when the engine is under load, such as during acceleration or climbing a hill.

Dirty fuel injectors can also cause rough idling, where the engine struggles to maintain a stable idle speed. In severe cases, the engine may even stall at idle, particularly if the fuel injectors are heavily clogged.

Another issue caused by dirty injectors is needle dancing or RPM needle fluctuations. This is when the needle on the tachometer fluctuates, even with a steady throttle. This fluctuation is caused by inconsistent amounts of fuel being delivered to the engine, leading to a rough ride, poor performance, and inefficiency.

A clogged fuel injector can also cause a noticeable drop in fuel efficiency as one of the most common symptoms. As the injectors become clogged, the engine may compensate by injecting more fuel than necessary, resulting in higher fuel consumption and more frequent refuelling.

In some severe cases, clogged fuel injectors may even prevent your car from starting. If the engine doesn't receive enough fuel for combustion, it won't be able to start. If the majority of injectors are blocked, you may experience this no-start condition.

Engine misfires

An engine misfire can be caused by a fuel injector that is failing or has failed. Fuel injectors are responsible for delivering fuel to the engine. When the fuel injection system fails, the engine fails. A clogged fuel injector can cause an abrupt loss of engine power, and if it continues to struggle to disperse fuel to the engine, it will eventually miss the fuel supply completely, causing the engine to misfire. This will be easily felt while driving and often requires immediate repair by a trained automotive specialist. As the engine misfires, it can quickly overheat and pre-ignite the fuel mixture.

There are several signs that a fuel injector is failing. For example, when a clogged injector causes the fuel supply to be irregular, the engine will move in surges rather than slow and gradual movements. A rough and irregular engine idle can also indicate a damaged fuel injector, as can reduced fuel efficiency.

There are several ways to troubleshoot an engine misfire. One user with a 2001 Toyota Tacoma 2WD 2.4L 4cyl reported that their truck ran fine from a cold start and continued to run fine once it had warmed up. However, once they stopped, shut off the engine, and restarted it while the engine was still warm, it would misfire and run terribly. They received a P0301 (cylinder 1 misfire) code and were advised to check their spark plug wires, as the resistivity rises with temperature and can affect the spark. They were also advised to try a different fuel station for a couple of fills and to check their fuel for water.

The user tried several fixes, including replacing all four spark plugs, swapping the first and fourth coils, cleaning the MAF sensor, cleaning the throttle body, checking and blowing out the engine air filter, and a visual check for vacuum leaks. None of these actions resolved the issue. The user was then advised to try troubleshooting the injector. They tried two tests: first, they pulled the injector lead when the vehicle was running poorly, and second, they pulled the injector lead when the vehicle was running well. They also tried changing the injector by moving injector #1 to cylinder #3 and vice versa. This did not resolve the issue, so they replaced all four injectors with refurbished ones, which fixed the problem.

Frequently asked questions