Ameer Randolph
Starting a fuel-injected car is not much different from starting a regular car. You turn the key, and the car either starts or it doesn't. However, the key difference lies in how you prime them. Instead of pumping fuel into the intake ports using a syringe pump primer, you use the pressurized fuel injection system itself to prime the engine. This involves turning the boost pump on to pressurize the system and setting the mixture to rich. The priming procedure is one of timing using the mixture, not counting pump strokes.
How to start a fuel-injected car
| Characteristics | Values |
|---|---|
| Similarities to starting a non-fuel-injected car | Just turn the key and it either starts or it doesn't |
| Differences to starting a non-fuel-injected car | You are using the pressurized fuel injection system itself to do the priming instead of pumping fuel into the intake ports |
| Priming procedure | Turn the boost pump on to pressurize the system and set the mixture to rich |
| What not to do | Do not count pump strokes |
| What not to do | Do not be late with the mixture after the engine starts or it will die |
| What not to do | Do not mess up the timing or you will flood the engine |
| What not to do | Do not start an FI engine that is hot on a hot day or it may cause vapour lock in the fuel distributor and lines |
| Starting in extreme cold | Turn key on and wait 5 seconds, then start |
| Starting in extreme cold | Crank it for a few seconds with your foot off the gas, then if it doesn't fire up, give it some gas |
| Starting in extreme cold | Turn key to run, leave for 5 seconds, then crank it |
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What You'll Learn
Fuel injected engines don't need priming
Unlike carbureted engines, fuel-injected engines do not require a primer. A manual fuel primer is used to inject vaporized fuel directly into one or more of the engine's cylinders to aid in starting. However, fuel-injected engines do not require this step as they do not suffer from the same issues as carbureted engines when cold.
Carbureted engines may not generate enough heat when cold to vaporize the fuel in their cylinders, resulting in the engine not starting. This is not an issue for fuel-injected engines, as the fuel is already vaporized before it enters the cylinders. Therefore, there is no need to prime a fuel-injected engine by injecting vaporized fuel manually.
The process of priming a carbureted engine typically involves unlocking and pulling out the primer knob, allowing it to fill with fuel, and then pushing the knob back in to force the fuel through small lines and nozzles, creating a fine mist as it is injected into the engine. This step is unnecessary for fuel-injected engines, which have their own built-in systems for ensuring proper fuel vaporization and injection.
While fuel-injected engines do not require manual priming, there may be other steps necessary to start them, especially if the car has been sitting for a long time or has a problem with the fuel system. For example, if the fuel tank is rusted and leaking, it may be necessary to set up a container to catch the leaking fuel before attempting to start the engine. Additionally, there may be specific procedures or requirements for starting a fuel-injected car, depending on the make and model of the vehicle.
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Turn the key and wait
Turning the key and waiting is a crucial step in starting a fuel-injected car, especially in extreme cold conditions. This process is slightly different from starting a carbureted engine, where you would typically pump the accelerator a few times, crank it, and then pump some more.
When starting a fuel-injected car, you would typically turn the key and wait for a few seconds. This wait time allows the system to pressurize and for the computer to communicate with the idle motor to position it for a cold start. The specific wait time can vary, with some recommending 5 seconds, while others suggest turning the key off for 10 seconds and then turning it back on and waiting for 5 seconds before cranking the engine. This step is important as it helps to ensure a smooth and successful start, especially in cold weather conditions.
During this waiting period, you can listen for the fuel pump to stop running. This sound indicates that the system has pressurized and is ready for the next step. It is important to ensure that you do not touch the throttle during this process. The waiting period also ensures that the coolant sensor, which acts as a choke, has adjusted the injector on time based on the temperature.
If the car doesn't start immediately, it may be due to flooding. In this case, you can try giving it a little gas or, as some suggest, putting the pedal to the floor. However, this should be done with caution as poorly adjusted linkage or floor mats can result in full-throttle flooding instead of shutting off the fuel. It is important to note that modern fuel injection engines are designed to shut off the fuel when the accelerator is held down all the way.
Overall, the "turn the key and wait" step in starting a fuel-injected car is an important part of the process, allowing the various systems to communicate and adjust for a successful start, especially in cold temperatures.
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Don't pump the accelerator
Pumping the accelerator pedal in a fuel-injected car is generally considered useless and will not help start the engine. This method was used in older carbureted vehicles to pump gas directly into the intake, enriching the fuel-air mixture and allowing for easier acceleration and engine startup. However, fuel-injected engines do not have a direct link between the throttle cable and the fuel pump, so pumping the accelerator pedal does not physically squirt fuel. Instead, the throttle regulates how much air (vacuum) is sucked through the carburettor, and pumping the pedal with the engine off achieves nothing.
In extremely cold conditions, slightly opening the throttle by a small amount can help the engine start easier by reducing pumping losses. Additionally, if the engine is flooded, holding the throttle fully open will turn off the injectors and allow the engine to clear. However, these are specific scenarios that do not apply to everyday engine starting procedures.
Some people may argue that pumping the accelerator pedal helps to prime the engine or send more fuel to the cylinders, but this is not accurate. Modern fuel-injected engines have computer-controlled fuel systems that regulate fuel delivery, and pumping the accelerator can confuse the engine control unit (ECU). Additionally, fuel does not change significantly in volume due to temperature fluctuations, so pumping the accelerator in hot conditions to compensate for fuel expansion is unnecessary.
It is worth noting that there may be exceptions to certain fuel-injected vehicles with specific issues. For example, a faulty fuel sensor or a stuck choke could potentially be mitigated by pumping the accelerator pedal. However, these are not standard procedures and are specific to individual cases.
In conclusion, it is generally advisable not to pump the accelerator pedal in a fuel-injected car. The engine control unit is designed to manage fuel delivery and ignition timing without any manual intervention, and attempting to assist the process by pumping the accelerator can do more harm than good.
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Listen for the fuel pump to stop
When starting a fuel-injected car, it is important to listen for the fuel pump to stop. This is because the fuel pump plays a crucial role in ensuring the correct fuel supply to the engine. By generating mechanical or electrical forces combined with pressure, the fuel pump transfers fuel from the fuel tank to the engine, specifically the carburetors or fuel injectors. These disperse fuel into the combustion chambers of the engine, where it is ignited to power the vehicle.
To check if your fuel pump is working, first, remove the fuel cap. Then, ask an assistant to turn the key to the "on" position while you listen near the gas tank opening. It is important to instruct your assistant clearly that they are not trying to start the car but simply turning the key so that the lights come on. Once the car is on, listen for the fuel pump. The fuel pump will only hum for two to three seconds if it is functioning properly.
If you do not hear the fuel pump, it may not be working properly. A faulty fuel pump can cause a range of issues, including difficult starting, engine surging, sputtering, or stalling. However, if the pump is not functioning, the cause may be as simple as a blown fuse. To check for a blown fuse, locate the fuel pump fuse and relay, and replace the fuse with another of the same amperage if necessary. After replacing the fuse, repeat the previous steps to determine if the issue has been resolved.
In some cases, a faulty fuel pump may be due to issues with the fuel pressure. Fuel pressure gauges can be attached to the engine to monitor fuel pressure and help prevent damage to the fuel pump and injectors. By applying external pressure to the car, you can compensate for any potential lack of pressure caused by a malfunctioning fuel pump. This method is even used by mechanics when dealing with a defective fuel pump.
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Set the mixture to rich
Setting the mixture to rich in a fuel-injected car involves adjusting the air-fuel ratio to allow more fuel into the engine's combustion chamber. This process can be fine-tuned by making adjustments to various components, such as sensors, filters, and regulators. Here are the detailed steps to achieve a rich mixture:
Firstly, it is important to understand the role of the oxygen sensor and the Mass Airflow Sensor (MAF). The oxygen sensor, located in the exhaust pipe, measures oxygen levels in the exhaust gases and provides this data to the Engine Control Unit (ECU). The MAF, on the other hand, monitors the amount of air entering the engine. If either of these sensors malfunctions or becomes contaminated, they can provide incorrect data to the ECU, leading it to inject more fuel than necessary, resulting in a rich mixture. Therefore, one way to set the mixture to rich is to intentionally adjust or replace these sensors to provide readings that will prompt the ECU to increase fuel injection.
Secondly, the fuel pressure regulator plays a crucial role in maintaining the correct air-fuel ratio. If this regulator malfunctions or becomes stuck in the open position, it can cause excessive fuel pressure, leading to a rich mixture. Adjusting the fuel pressure regulator can be a way to intentionally create a rich mixture.
Thirdly, a restricted air intake or a clogged engine air filter can limit the airflow into the combustion chamber. With less air available, the fuel may not burn completely, resulting in excess fuel and a rich mixture. Therefore, intentionally restricting airflow or neglecting to replace air filters can be a way to set the mixture to rich.
Finally, regular maintenance of spark plugs is essential. If spark plugs are worn out or malfunctioning, they may not fire properly, leaving excess fuel in the cylinders that is not burned off. This can contribute to creating a rich mixture.
It is important to note that while these adjustments can lead to a rich mixture, they may also have negative consequences, including decreased fuel efficiency, reduced engine performance, increased emissions, and potential engine damage. Therefore, it is recommended to consult a professional or a mechanic before making any significant changes to your vehicle's settings.
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Frequently asked questions
Turn the key to the on position and wait for the system to pressurize. Then, turn the key to start the engine. If this doesn't work, try holding the accelerator pedal to the floor.
Try turning the key off for 10 seconds, then to the run position for 5 seconds, and then try to crank it.
Carbureted engines require priming and are prone to flooding. Fuel-injected engines are more reliable and don't need priming.
Turn the boost pump on to pressurize the system and set the mixture to rich.
