Rajan Wilcox
If your car has a bad fuel injector, it may not start. A bad fuel pump leads to low fuel pressure and reduced efficiency. If your car won't start, let the engine cool, then find the fuel pressure test port under the hood and attach a gauge. You can also try spraying a small amount of fuel into the air intake while someone cranks the engine. If the engine kicks, you know it's a fuel problem. If there is no injector pulse while cranking, check for power going to the injectors. If your car has a clogged fuel system, it's best to call a ride or have your vehicle towed instead of trying to drive it.
How to start a car with a bad fuel injector
| Characteristics | Values |
|---|---|
| Engine cranks but won't start | While someone cranks the engine, spray a little amount of fuel into the air intake and if the engine kicks and wants to start, then you know it's a fuel problem and not a spark problem |
| Fuel pressure | Get a fuel pressure gauge and check for fuel pressure at the rail. You should be getting between 55-62 psi |
| Fuel pump | Put the fuel supply line into an empty water bottle and have someone turn the key just to run for a few seconds and off again. If fuel comes out, then your pump is good |
| Injector pulse | Check for power going to the injectors key and while cranking (could be a faulty relay, blown fuse, or a wiring issue) |
| Spark | Try starting fluid in the intake and see if it remains running |
| Fuel filter | The fuel filter may be clogged |
| Fuel injectors | Replace clogged diesel fuel injectors for your make and model to improve fuel efficiency |
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What You'll Learn
Check for spark and fuel in your car
If your car isn't starting, there are four ingredients to check: spark, air, fuel, and compression.
Checking for Spark
Spark plugs are found in all gasoline engines and are responsible for igniting the air/fuel mixture inside the engine. Age, use, and poor fuel quality can contribute to a dirty spark plug that doesn't spark properly. To test a spark plug, you can use a spark tester, which is a big spark plug that measures the strength of the spark. Alternatively, you can pull out a spark plug and ground the tip to the frame while someone else cranks the engine. If you see a spark, then your spark plugs are working. If not, you may need to replace the spark plug with a new one of the same kind.
Checking for Fuel
To check for fuel, you can use a fuel pressure gauge to ensure there is ample pressure. If your vehicle has a carburetor, you can also check the mechanical fuel pump by unplugging the fuel hose from the carburetor and feeding it into a glass jar. Turn the car over and if the jar fills with fuel, your fuel pump is working.
Checking for Air
To check for air, you can listen for vacuum leaks or cracks in the air induction system. If you suspect a leak, spray a small amount of starting fluid near the suspected spot. If the engine changes its tune, you have a vacuum leak.
Checking for Compression
To check for compression, you can buy or rent a compression tester, which is a gauge attached to a hose with a fitting at the end. Pull your spark plug wire and thread the tester into your spark plug hole, then turn your engine over with the key.
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Test fuel pressure
Testing the fuel pressure is an important step in diagnosing issues with your car's fuel system, including problems with the fuel injectors. Here is a detailed guide on how to test the fuel pressure:
Firstly, it is important to note that you will need a fuel pressure test kit. These kits typically consist of a gauge designed to read fuel pressure and a fuel hose. Basic fuel pressure test kits are available for purchase at a relatively low cost. Additionally, you will need an assistant to help you rev the engine during the testing process.
Before beginning the test, consult your vehicle owner's manual to determine the recommended fuel pressure level for your specific car. This information is crucial as it will serve as a reference point for interpreting the results of the test.
Now, open the hood of your car and locate the fuel pump test point, usually positioned beside the fuel injectors. Remove the cap attached to the fuel pump test point and attach the fuel hose from the kit to this point. Ensure that any air is released from the fuel pressure gauge before taking readings.
With the engine off, turn the ignition key to the "on" position. At this point, the fuel pressure gauge should display a reading within a certain range, depending on the type of fuel injection system your car has. For direct port injection systems, the reading should be between 45 psi and 58 psi. On the other hand, throttle body injection systems typically show readings between 13 and 17 psi. If no pressure is indicated, recheck the connections and adapters to ensure an accurate reading.
If there is still no pressure, this may be indicative of a faulty fuel pump, fuel pump relay, or fuse. Additionally, you can start the engine and observe the fuel pressure gauge. The pressure should drop by approximately 5 psi from the static prime pressure. Then, snap the throttle, and the fuel system pressure should increase by about 5 psi, suggesting that the fuel pump and pressure regulator are functioning correctly.
If the fuel pressure does not respond as expected, further inspection of the regulator vacuum feed line is warranted. If this appears to be functioning correctly, the issue may lie with the fuel pressure regulator itself.
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Check for injector pulse
Checking for an injector pulse is a way to diagnose a fuel injector issue. A fuel injector supplies a fine mist of fuel to the engine, and when this process is interrupted, it can cause engine problems. A faulty fuel injector can cause the engine to misfire, sputter, and shake, leading to what is known as "rough idling". This can also cause the vehicle to stall and the engine to fail to start.
To check for an injector pulse, you will need to use a noid light. This device is placed where the injector connects to test for a pulse. If there is no pulse, it could be due to a faulty crankshaft sensor circuit or a missing 12-volt positive supply to the injectors. It is also possible that the ignition module is faulty, as this is required to fire the injectors.
Another way to check for injector pulse is to test the fuel pump relay. The fuel pump delivers gasoline to the fuel injector, so if the pump relay is not working, the injector will not function. You can also check the fuel pressure gauge to ensure it is within the correct range (55-62 psi). If the pressure is low, it could indicate a problem with the fuel injector.
It is worth noting that a flashing "Check Engine" light on your dashboard could indicate a dirty or malfunctioning fuel injector. However, this light could also signify other issues, so further diagnosis is required.
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Check for power going to injectors
To check for power going to the injectors, you will need to perform a series of tests. Firstly, ensure you have put on the necessary safety gear, including work gloves and eye protection. It is also recommended to work outside or in a well-ventilated area.
Begin by turning the key to the "on" position without starting the engine. This will activate the vehicle's electrical system without engaging the engine's starter. Set up a DVOM or a voltmeter to measure DC voltage, ensuring it is set to the lowest range if the meter does not auto-range. Touch the negative lead of the DVOM or voltmeter to a ground source, such as an unpainted piece of the car's frame under the hood.
Now, locate the injector wiring harness or connector. There may be a slide lock that needs to be moved before pressing down on the tabs to remove the wiring harness. With the key still in the "on" position, gently probe both sides of the injector wiring connector with the voltmeter or test light. One of the wires should register around 12 volts on the meter or illuminate the test light. If neither wire reacts, test the fuel injector fuse in the PDC. If the fuse is intact, you may need a fuel injection wiring diagram to trace the wire and repair the connection.
Additionally, you can use a test light or voltmeter to check the injector signal from the computer. Attach the test light lead or voltmeter to the positive side of the battery, and start or crank the engine. Probe the opposite side of the injector connector from the power circuit. The test light should flicker in response to engine RPM/Load, indicating that the injector is receiving power and pulse signals from the computer.
It is important to note that these tests assume a basic understanding of automotive systems and electrical principles. If you are unsure or uncomfortable performing these tests, it is recommended to consult a professional mechanic or seek advice from a trusted source.
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Consult a professional
If you're experiencing issues with your fuel injectors, it's important to consult a professional mechanic for assistance. They will have the expertise and equipment to properly diagnose and address the issue. Here are some reasons why consulting a professional is the best course of action:
Expertise and Experience: Professional mechanics have extensive knowledge about different vehicle systems, including fuel injection systems. They can quickly identify the root cause of the problem, whether it's a faulty fuel injector, a clogged fuel filter, or an issue with the fuel pump. Their experience means they've likely encountered similar issues before and know the most effective solutions.
Specialised Tools and Equipment: Mechanics have access to specialised tools and diagnostic equipment that may be required to fix the issue. For example, they may use an OBD-II scanner, a portable digital device that can quickly diagnose engine trouble and provide error codes to narrow down the problem. They can also perform fuel pressure tests to check if the issue is related to low fuel pressure, which could be caused by faulty injectors or a faulty fuel pump.
Safety: Working on a car's fuel system can be dangerous, especially for those who are inexperienced. Fuel injectors operate under high pressure and dealing with flammable fuel requires proper safety precautions. Professional mechanics have the training and knowledge to work safely on these systems, reducing the risk of injury or accidents.
Cost-effectiveness: While it may seem costly to consult a professional, it can actually save you money in the long run. Mechanics can provide accurate diagnoses and efficient repairs, preventing you from wasting time and money on incorrect or ineffective fixes. Additionally, attempting to repair a fuel injection system without proper knowledge can lead to further damage to your vehicle, resulting in even more costly repairs.
Warranty and Guarantee: Repairs performed by professional mechanics are often backed by warranties or guarantees. This means that if the issue persists or something else goes wrong shortly after the repair, you can take your car back for further diagnosis and repair at no additional cost. This provides peace of mind and ensures that you're protected in case the problem is not fully resolved.
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Frequently asked questions
If your car has never misfired before, it is likely that the electronic control of the injectors is faulty.
Swap the spark plugs between cylinders 1 and 2, and the ignition coils from cylinder 1 and 3. If the misfire follows one of those parts, then you know what needs to be replaced.
If the injector is stuck closed, the cylinder will run lean and burn a hole in the cylinder or valve. If it's stuck open, you can technically drive, but it will damage the catalytic converter and waste fuel.
While someone cranks the engine, spray a little amount of fuel into the air intake. If the engine starts, you know it's a fuel problem.
Figure out which injector is bad and replace it as soon as possible. A local parts store will loan out a code reader to help pinpoint the problem.
