The Evolution Of Fuel Efficiency: Double Fuel Pressure

A car's fuel pump is a critical component of its powertrain system, transferring fuel from the tank to the engine. The pump's pressure can vary, with low-pressure pumps operating at 10-15 psi and high-pressure pumps reaching up to 30,000 psi. The pump's pressure is essential as it can impact the car's fuel economy and performance. For example, a weak pump can lead to low fuel pressure, resulting in a decline in power and, eventually, a lack of fuel delivery to the engine. Upgrading to a higher-flow pump can provide benefits, but it may also increase stress on the fuel system, unnecessarily heat the fuel, and draw more current. Therefore, understanding the reasons behind pumping double the fuel pressure in cars is crucial for maintaining optimal vehicle performance and efficiency.

Fuel pump failure signs

Fuel pumps are designed to last the entire life of a car, but they can still fail prematurely. Here are some signs that your fuel pump is failing or has failed:

• Whining or whirring noise from the fuel tank: A damaged fuel pump may make a loud, whining sound, indicating a problem. This noise could be due to low fuel or contaminated fuel, but if the pitch is higher than the usual low hum, it could mean the pump is faulty.
• Trouble starting the car: If the fuel pump is unable to deliver enough fuel to the engine, the car will struggle to start and run. A worn pump loses pressure, starving the engine of fuel.
• Engine sputtering or stalling: A faulty fuel pump may cause the engine to sputter and threaten to stall, especially at higher speeds or when the engine is under stress (e.g., towing a heavy load or driving uphill).
• Engine surging: When too much fuel is sent to the engine, it can cause the vehicle to surge, resulting in speed spikes and drops even when you're not touching the pedals.
• Overheating: An old or worn pump can get too hot, causing the entire engine to overheat.
• Loss of power: If you experience a loss of power when driving up steep inclines or carrying a heavy load, it could be due to a faulty fuel pump being unable to provide enough fuel to meet the engine's demand.
• Lower fuel efficiency: A damaged fuel pump can allow excess fuel into the engine, causing you to burn more gas than usual and resulting in more frequent trips to the gas station.
• Car cuts off for no reason: A failing fuel pump may cause your car to cut off while driving, and this will happen more frequently as the problem worsens.
• Car stutters and stumbles: Intermittent coughing and sputtering that can't be explained could be a sign of a bad fuel pump.

It's important to note that some of these issues could be caused by other factors, such as bad fuel, damaged fuel lines, or a clogged fuel filter. Therefore, it's recommended to have a comprehensive inspection and diagnosis performed by a qualified technician to identify the root cause.

Fuel pump types

Fuel pumps are components used in liquid-fuelled engines to transfer fuel from the tank to the engine. They are often found in internal combustion engines.

There are three main types of fuel pump: mechanical, electric, and high-pressure. The type of fuel pump used depends on the type of vehicle and engine.

Mechanical Fuel Pumps

Mechanical fuel pumps are typically used in carbureted engines, such as those found in older cars, lawnmowers, and power tools. They operate at a relatively low fuel pressure of 10-15 psi (0.7-1.0 bar). There are two main types of mechanical pumps: diaphragm pumps and plunger pumps. Diaphragm pumps use a diaphragm to suction fuel, while plunger pumps use a reciprocating plunger to suction and distribute fuel.

Electric Fuel Pumps

Electric fuel pumps are commonly found in fuel injection systems, which are standard in modern cars. They generate high pressure to distribute fuel from the pump. Electric fuel pumps are typically located inside the fuel tank to reduce the risk of fire and keep the pump cool.

High-Pressure Fuel Pumps

High-pressure fuel pumps are used in combustion ignition engines for the direct injection of fuel into the combustion chamber. These pumps operate at pressures of more than 200 Pascals (over 2,000 psi). This type of pump is particularly complex and durable to manage such high pressures.

Other Types of Fuel Pumps

In addition to the three main types, there are also port and helix pumps, which are commonly used in marine diesel engines due to their simplicity, reliability, and scalability. Rocket engines, on the other hand, use turbopumps to supply fuel and oxidizer into the combustion chamber.

Fuel pump location

Fuel pumps are indispensable components that transmit fuel from the fuel tank to the injectors, maintaining a specific pressure. If the fuel pump isn't functioning properly, the engine may not run well or may not run at all. In most modern vehicles, the fuel pump is located inside the fuel tank, which helps keep the pump cool and ensures a consistent fuel supply. This is also the case for primary fuel pumps in vehicles with fuel injection systems.

However, in some older models or specific vehicle types, the fuel pump may be located outside the tank, typically along the fuel line or on the engine block. Additionally, vehicles with GDI (gasoline direct injection) systems, often found in newer high-performance models, have a secondary, high-pressure pump. This is usually mounted near the fuel rail within the engine compartment. Its role is to increase fuel pressure to the extremely high levels required by GDI systems, allowing for more precise fuel delivery directly into the combustion chamber.

Accessing the fuel pump can vary across different vehicle models. Some vehicles have a fuel pump access door located underneath the rear seat, allowing access from inside the cabin. In other vehicles, accessing the pump requires dropping the fuel tank and disconnecting various components such as electrical connections, fuel lines, and possibly the exhaust system.

Fuel pump testing

To perform a fuel pressure test, you can use a fuel pressure gauge, which is commonly available at auto parts stores. Hook the pressure gauge to the fuel pump test fitting, usually located near the fuel injectors. Then, have an assistant rev the engine while you check the gauge. If the needle doesn't move, it indicates a problem with the fuel pump.

You can also perform an electrical test to check the fuel pump. Check the fuel pump fuse in the fuse box. If it is blown, replace it. If no fuses are blown, listen for the fuel pump relay clicking when the key is turned. Additionally, check the voltage at the pump itself to ensure it is receiving power. Perform a drop test using a voltmeter to ensure proper voltage and grounding. If this test reveals nothing, the fuel pump likely needs to be replaced.

It is important to note that other issues can mimic a faulty fuel pump, so performing a thorough diagnosis is crucial before replacing any parts.

Fuel pump replacement

When to Replace a Fuel Pump

If you notice anything strange about your engine's performance, have it checked out as soon as possible. Some common symptoms of a faulty fuel pump include:

• Difficulty starting the car
• Loss of power while driving
• Rough run or stalling
• Strange, high-pitched whining noises coming from the fuel tank area

Preparations for Replacing a Fuel Pump

Before starting, gather all the necessary tools and equipment, including a new fuel pump, fuel filter, and any other components specific to your vehicle. If you can, reduce the amount of fuel in the tank to minimise spillage and mess. Have a safe and accessible workspace and take proper safety precautions, such as pulling the fuel pump relay and disconnecting the battery.

How to Replace a Fuel Pump

• Relieve the fuel system pressure.
• Locate the fuel tank and remove it from the vehicle. This process varies from vehicle to vehicle, and you may need to use a jack to support the tank as you lower it.
• Note the fuel line connections and wiring before removing the old pump.
• Remove all connections, turn the large lock nut to free the old pump, and pull it out.
• Reassemble the fuel system and test the new fuel pump to ensure everything is functioning properly.

Tips for Replacing a Fuel Pump

• Work in a well-ventilated area, preferably outdoors, to minimise the risk of fire and inhaling harmful fumes.
• Always wear safety glasses and gloves to protect yourself from fuel spills and splashes.
• Drain the fuel tank to reduce the risk of spills and make it lighter and easier to handle.
• Clean around the fuel pump to prevent dirt and debris from falling into the fuel tank.
• When replacing the fuel pump, consider replacing related components such as the fuel filter, fuel pump strainer, and fuel tank O-ring or gasket.

Frequently asked questions