Mercedes Mullins
Fuel injectors are a crucial component of modern automotive engines, delivering a precise amount of fuel to the engine cylinders for combustion. However, issues with fuel injectors can leave drivers stranded, as evident from numerous forum posts and discussions online. When fuel injectors fail to receive power, it can lead to a vehicle not starting or experiencing poor performance. In such cases, troubleshooting involves checking power sources, fuses, relays, and wiring, as well as verifying the functionality of the fuel pump and crankshaft/camshaft position sensors. In some instances, a faulty PCM (Powertrain Control Module) or ECU (Engine Control Unit) may be the culprit, requiring reprogramming or replacement.
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What You'll Learn
The PCM (Powertrain Control Module) triggers the fuel injectors
The Powertrain Control Module (PCM) is an essential automotive component, acting as a control unit in motor vehicles. It is often referred to as the "brain" of the car's engine control system, coordinating and managing a wide range of functions.
The PCM plays a crucial role in triggering the fuel injectors. It receives data from various sensors distributed throughout the vehicle, including parameters such as engine speed, coolant temperature, throttle position, and oxygen levels in the exhaust. By processing this information, the PCM regulates the fuel injection process, including the fuel injection rate, to ensure optimal engine performance and efficiency.
The PCM's role in fuel injection is further enhanced by its integration with other vehicle systems. It communicates with the Body Control Module, the anti-lock braking system, traction control, and even the climate control system. This networking ensures that the vehicle's systems work harmoniously through constant small adjustments, optimizing the overall performance and driveability of the car.
Additionally, the PCM's functionality extends to security features. It is designed to look for coded signals from a key fob or the key itself when a motorist enters the vehicle. If the PCM does not detect the correct code, it will not activate the starter or energize the fuel pump circuit, potentially causing no-start issues.
Maintaining the PCM in good condition is vital for the longevity and performance of the vehicle. Regular maintenance includes keeping its electrical connections clean and secure, ensuring the sensors and actuators it relies on are functioning correctly, and promptly addressing any issues indicated by the check engine light.
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The PCM sends a ground to each injector
The Power Control Module (PCM) is responsible for sending a ground to each fuel injector. The PCM controls the fuel injectors and triggers them based on the cam position and crank position sensor signal. The PCM determines the proper ignition timing according to input received from the crankshaft position sensor.
The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off. This is done by applying voltage to the fuel injectors with the ASD relay via the PCM. The PCM will adjust the injector pulse width by turning the ground circuit to each individual injector on and off.
If the PCM is faulty, the injectors may not fire. However, there are other potential issues that could cause this problem, such as a bad wire or a faulty injector not getting power. It is also possible that the wire from the PCM to the injector is cut, or the wire that gives the injector power from the fuel pump relay is cut.
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The fuel pump relay supplies power to the injectors
The fuel pump relay is a crucial component of a combustion engine, responsible for supplying the necessary fuel to the engine for its functioning. When the ignition is turned on, the fuel pump relay provides a consistent voltage to the fuel pump, ensuring the engine receives the fuel it needs to operate. This process is controlled by the ignition or the power control module.
The fuel pump relay is typically located in the fuse box in the engine bay, often in a long black box alongside other fuses and relays. It is easily identifiable by its cube shape and electrical plug-like connections. A faulty fuel pump relay can cause the fuel pump to malfunction, resulting in startup issues or sudden engine stalls. Therefore, it is essential to regularly inspect the fuel pump relay for any signs of corrosion or overheating, which can disrupt the proper flow of current.
Now, specifically regarding the fuel injectors, the fuel pump relay plays a vital role in supplying power to them. The injectors require a constant 12V supply, and the fuel pump relay ensures this voltage is delivered. In some vehicles, like the 2006 Chrysler 300, the fuel pump relay supplies power to all the fuel injectors. Then, based on the cam position and crank position sensor signal, the PCM triggers the injector to release fuel.
It is worth noting that there are different configurations for powering the injectors. Some vehicles use the main relay, while others use the fuel pump relay. In certain cases, the injectors are powered by the main relay, and the fuel pump and related components are powered by the fuel pump relay. However, it is crucial to ensure that the injectors and the MicroSquirt controller are powered by the same relay to prevent issues with grounding and potential engine flooding.
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The PCM may need reprogramming to eliminate VATS
The Power-train Control Module (PCM) is responsible for sending power to the fuel injectors. It does this by triggering the injector based on the cam position and crank position sensor signal. The PCM fires the injectors by sending a ground to each injector.
The PCM may need reprogramming to eliminate the Vehicle Anti-Theft System (VATS). VATS is the general term for vehicle anti-theft systems. GM has used PASSKEY, PASSLOCK, and many variations and progressions of it through the years, but VATS is always the term used in the service manuals to refer to the security system. The Passlock family of anti-theft systems are still in use today.
The PCM can be reprogrammed to eliminate VATS. This can be done by downloading the PCM's file to a laptop, disabling VATS, saving it, and then uploading it back to the PCM. However, if the PCM is reprogrammed incorrectly, the security light on the dash may stay on all the time. It is understood that if VATS is eliminated, no security light should ever illuminate.
There are other ways to eliminate VATS without reprogramming the PCM. One method is to wire around the PCM to the fuel pump and give it power with any "keyed" source. This means that when the key is "on", the pump is on. Another method is to jump the purple wire to the yellow wire on the relay. This will make the starter circuit work without VATS or the BCM. However, this modification is dangerous for a street car as the engine will crank when the key is turned, regardless of where the clutch or tranny is.
If the PCM is faulty, the car may not start even with a fuel source. However, there are a few things to check to make sure that is the case.
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A bad crankshaft/camshaft position sensor may be the cause
The crankshaft position sensor is a multifunctional sensor that plays a vital role in engine management systems. It monitors the position and rotational speed of the crankshaft, sending critical data to the Engine Control Unit (ECU). This real-time data ensures that the engine operates smoothly and efficiently, optimizing fuel injection and ignition timing.
When the crankshaft position sensor fails, it can lead to engine problems such as misfires, reduced fuel economy, and even engine failure. In most cases, a faulty crankshaft position sensor will result in an engine that cranks but fails to start or run. This is due to the loss of timing signals, which are necessary for determining the correct spark plug firing sequence and controlling fuel injector and ignition timing.
The camshaft position sensor is equally important, as it works with the crankshaft position sensor to ensure accurate timing. This sensor monitors the speed of the camshaft and, together with the crankshaft sensor, determines which cylinder is firing and synchronizes the fuel injector and coil firing sequence.
To determine if a bad crankshaft/camshaft position sensor is causing the issue, specific tests can be performed. However, it is important to refer to the vehicle's service manual to identify the correct procedure for the specific sensor type. In some cases, accessing live data from the crankshaft position sensor may not be possible, making troubleshooting more challenging.
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Frequently asked questions
There could be a few reasons for this. The wire from the PCM to the injector could be cut, or the wire that gives the injector power from the fuel pump relay could be cut. Alternatively, the PCM itself might be faulty. You should check the wiring diagram to see what sends power to the injectors and work your way through each component and connection.
The PCM sends a signal to the fuel injector to open. The PCM fires the injectors by sending a ground to each injector. The fuel enable command is given from the PCM when the theft deterrent module detects the proper pellet resistance from the key.
You can test whether your fuel injectors are receiving power by using a noid light. If the injectors are not getting 12v, you should suspect the TDM first, then the wiring.
