Fuel Levels And Gas Tank Pressure: What's The Link?

Low fuel pressure can cause a range of issues with your vehicle, from poor engine performance to safety hazards. It is caused by a number of factors, including a weak fuel pump, clogged filter, faulty regulator, or damaged fuel lines. When the fuel pressure is low, the engine doesn't receive the right amount of fuel, leading to problems such as engine misfires, stalling, and poor acceleration. In this article, we will explore the causes, symptoms, and solutions for low fuel pressure, as well as the risks of ignoring this issue.

Fuel pump failure

Running the Fuel Tank Low

A leading cause of fuel pump failure is running the fuel tank low. This is particularly critical for late-model vehicles without a fuel pressure return system. Running a vehicle out of fuel even once can permanently damage the fuel pump. When the fuel level is low, the pump has to work much harder to produce the same pressure as it must draw the fuel in rather than relying on the weight of the fuel to push it into the pump. A low fuel level also means there is less fuel available to dissipate heat and lubricate the pump. The combination of an overworked pump, reduced cooling, and insufficient lubrication will likely damage the fuel pump.

Fuel Contamination

Fuel contamination occurs when corrosion, debris, and moisture enter the fuel tank, bringing visible contaminants that can clog the fuel pump and other components. Sometimes the tank itself is rusty and deposits rust particles. Contaminants in the fuel tank are drawn through the fuel pump, and while the strainer on the pump will try to remove larger particles, many smaller particles pass through and cause damage. Debris that enters the pump wears the commutator and brushes on the motor.

Electrical Issues

Electrical issues are often a direct consequence of fuel contamination. As the brushes and commutator wear, the motor pulls more amperage to produce the same pressure. The additional amperage from a worn pump often burns the connectors inside the fuel pump. Burned connectors and harnesses on failed pumps are extremely common, and a damaged connector can lead to a replacement pump failure if not replaced.

Insufficient Filtration

The fuel filter is the first line of defence against contaminants, and a clogged filter reduces the flow of fuel and causes symptoms such as backfiring, stalling, or hesitation. Most late-model vehicles do not have separately replaceable fuel filters, so a clogged filter may mean a new fuel pump is required.

Natural Wear and Tear

Like most vehicle components, natural wear and tear is an unavoidable cause of fuel pump failure. Fuel pumps are often out of sight and out of mind for most people, only requiring repair or replacement when they fail.

Clogged fuel filter

A clogged fuel filter can cause a host of problems, from reduced engine performance to engine damage. The fuel filter is responsible for removing contaminants from the fuel before they can reach the engine. Over time, the filter will begin to collect and hold onto particles, which can eventually clog the filter and impact its effectiveness. This is why regular servicing and replacement of the fuel filter are essential.

• Difficulty starting the engine: If your fuel filter is clogged, it can restrict the flow of fuel to the engine, making it difficult to start. You may notice the engine cranking longer than usual before turning over.
• Sluggish acceleration: A clogged fuel filter can restrict the flow of fuel during acceleration, causing the engine to hesitate or stumble as it demands more fuel for increased power and speed.
• Rough idling: Most vehicles have some level of vibration at a stop, but more intense vibrations or lurching when accelerating can indicate a clogged fuel filter.
• Engine stalling: If the fuel filter is severely clogged, the insufficient fuel supply may cause the engine to stall out completely, especially at idle.
• Unusual noises: The fuel pump has to work harder to push fuel through a clogged filter, which can cause it to produce strange noises that may be heard inside the vehicle.
• Check Engine Light comes on: Low fuel pressure caused by a clogged filter may trigger the Check Engine Light.

To prevent these issues, it is recommended to regularly replace the fuel filter according to the vehicle manufacturer's maintenance schedule. The maintenance interval for a fuel filter varies depending on the make, model, and year of the vehicle. Some vehicles may need a replacement every 20,000 miles, while others can go up to 150,000 miles on the same fuel filter. It is also important to use high-quality fuel and additives to minimize debris buildup and keep injectors clean.

Faulty fuel pressure regulator

A faulty fuel pressure regulator can cause a host of issues in your vehicle, as it plays a critical role in maintaining the correct fuel pressure in the fuel rail. Here are some common symptoms of a faulty fuel pressure regulator:

• Engine Performance Problems: A bad fuel pressure regulator can cause a loss of fuel pressure, leading to engine performance issues such as hard starting, rough running, stalling, and a lack of power.
• Check Engine Light Illuminated: The engine computer detects issues, including those caused by a faulty regulator, that could increase emissions. This triggers the check engine light, and a corresponding diagnostic trouble code (DTC) is stored.
• Black Smoke from the Exhaust: A faulty regulator can cause the engine to run rich, resulting in black smoke from the tailpipe.
• Fuel in the Regulator's Vacuum Line: A ruptured diaphragm within the regulator can cause fuel to be drawn into the vacuum line and the engine's intake manifold.
• Vehicle Cranks But Doesn't Start: A faulty regulator can prevent the engine from receiving adequate fuel pressure, resulting in a cranking but non-starting condition.
• Engine Misfires: A faulty regulator can disrupt the air-fuel ratio, leading to engine misfires and reduced engine performance.
• Decreased Power, Fuel Efficiency, and Acceleration: A bad regulator can cause a reduction in engine power, poor acceleration, and decreased fuel efficiency due to an incorrect air-fuel mixture.
• Fuel Leaks: Failure of the regulator's diaphragm or seals can lead to fuel leaks, which pose a safety hazard and impact engine performance.
• Noisy Fuel Pump: A failing fuel pressure regulator can cause the normally quiet fuel pump to make an irritating whirring noise, especially noticeable in slow-moving traffic.

Leaking fuel injectors

• Hard starting when the engine is hot: A leaking fuel injector is often the cause of a hard-starting engine, especially when the engine is warm. This is because the fuel rail pressure has dropped, causing the spark plugs to become flooded.
• Increased fuel consumption: Leaking fuel injectors can waste fuel, leading to higher fuel consumption and reduced fuel efficiency.
• Fuel odours inside and around the car: A strong fuel smell inside the cabin or around the car is a sign of a leaking fuel injector. This is caused by fuel leaking inside the engine compartment or dripping underneath the car.
• Oil thinning: Leaking fuel injectors can cause fuel to escape into the intake manifold and mix with the engine oil. This can lead to oil thinning, which can result in engine bearing damage, scorched cylinder sidewalls, and even an explosion inside the engine.
• Rough engine performance: A leaking fuel injector can cause the engine to run unevenly, with unusual noises and vibrations. This is often due to insufficient fuel delivery to the engine.
• Check engine light: Modern cars have sensitive computerized devices that can quickly detect problems caused by a faulty injector. The check engine light coming on is often the first warning sign of a leaking fuel injector.

To prevent leaking fuel injectors, regular cleaning and inspection are important. Proper fuel injector cleaning techniques can restore injectors to like-new condition at a fraction of the cost of new ones. Additionally, regular maintenance of the fuel system, including fuel filters, fuel lines, and the fuel pump, can help prevent issues that can lead to leaking injectors.

Restricted fuel lines

Over time, fuel lines may develop cracks, get damaged, or become clogged due to exposure to the elements, mechanical strain, or the buildup of dirt and contaminants. This can result in restricted fuel flow, leading to low fuel pressure.

The fuel lines transport fuel from the tank to the engine, and any restriction or leakage in the lines can reduce the pressure and impact the delivery of fuel to the engine. This, in turn, can cause engine misfires, hard starting, stalling, poor acceleration, and reduced fuel efficiency.

To prevent restricted fuel lines, regular maintenance and inspections are crucial. Routine checks can help identify early signs of wear, damage, or leaks, allowing for timely repairs or replacements. Additionally, using high-quality fuel and fuel additives can help minimize debris buildup and promote better fuel flow.

It is important to address issues with restricted fuel lines promptly, as neglecting low fuel pressure can lead to serious engine problems and safety hazards.

Frequently asked questions