A fuel pump pushes fuel from the tank to the vehicle's engine, which powers your car. The fuel pump will generally be part of a full fuel pump assembly which will include the sending unit, level arm and fuel filter.
The types of fuel pumps include:

• Mechanical Fuel Pump

Mechanical fuel pumps are found in vehicles with engines that use a carburetor, which tend to be older vehicles. All new cars will not have this style of fuel pump.

• Electric Fuel Pump

Electric fuel pumps is the most common type of fuel pump you will find in vehicles driving on today's roads. You will find the electric fuel pump directly inside the fuel tank, and works with the fuel injectors in your car. In comparison to the mechanical fuel pump, the electric fuel pump typically pumps gas at a higher pressure.

Fuel pumps come in different shapes and sizes and with varying features. When searching for a replacement fuel pump, drivers must ensure that they choose the right fit for their engine. Different factors affect the selection of a fuel pump. However, the most important determining factors include the engine’s fuel efficiency, horsepower, voltage, and the maximum fuel system pressure.

Engine Fuel Efficiency

The efficiency of an engine is the amount of fuel required to produce 1 HP for 60 minutes. It is also known as the engine’s Brake Specific Fuel Consumption (or simply BSFC). Modern engines fall into three broad categories based on their BSFC rating.
• Engine Type: Normal Aspirated Engine
• Industry B.S.F.C Standards: .45 – .5
• Engine Type: Super charged engines (nitrous combinations)
• Industry B.S.F.C Standards: .55 – .60
• Engine Type: Turbo charged engines (forced induction)
• Industry B.S.F.C Standards: .6 – .65
These figures are just general guidelines. Drivers can determine the exact BSFC of their engine by conducting an engine dyno test.

Fuel Volume

A car’s fuel volume is reliant on its horsepower rating and BSFC. Drivers can calculate the average fuel requirement by multiplying these two values. For instance, for a 650 HP engine with a .45 BSFC, the amount of fuel required equals 660 multiplied by .45, which is 292 lbs of fuel. The more efficient the engine, the higher the BSFC and the amount of fuel required. When shopping for an electric fuel pump, it is best to play it safe. Drivers who are unsure of their car’s horsepower should consult with an experienced mechanic. Basing calculations on the wrong HP estimates can lead to serious engine damage.

Voltage

Modern electric fuel pump systems rely on electricity. Fuel injectors are designed to work within certain voltage limits. When choosing a fuel pump, drivers must select pumps that fit with the voltage output of the engine. For instance, attaching a fuel pump designed to work with 12 volts to another vehicle that outputs 13.5 volts, increases the volume of fuel being pumped by as much as 40 percent. This can quickly lead to pump issues. Excessive voltage can also affect the fuel pump relay.

Diagnosing a Faulty Fuel Pump

The biggest indication of a faulty fuel pump is an irregular supply of fuel to the engine. When a fuel pump is bad, the vehicle may begin to lose power, jerk while in motion, or simply not start. If a fuel pump develops an irreparable problem, drivers can opt to either replace the faulty unit on their own or take it to a skilled mechanic.
Because fuel is highly flammable, it is important that drivers only perform the replacement on their own if they are confident of achieving this successfully. It also helps if drivers work with a pump replacement guide to figure out key issues like where the fuel pump is located.
If for any reason you cannot find your fuel pump by searching your vehicle's year, make and model, the best way to find the right fuel pump for your car is by searching by the Original Equipment Manufacturer (OEM) part number off your stock fuel pump assembly. The OEM part number can be found directly on the part itself.

1. Whining Noise From the Fuel Tank

One of the first symptoms of a problem with the fuel pump is a loud whining sound. An old or worn fuel pump may produce a noticeably loud whine or howl while running. Most fuel pumps will produce a quiet hum during their normal operation, however, an excessively loud whine coming from the fuel tank is usually a sign of a problem. There may not be enough fuel, a damaged pump, or contaminated fuel inside the system.

2. Difficulty Starting

Another symptom commonly associated with a problematic fuel pump is difficulty starting. Because fuel pumps constantly run whenever the ignition is turned on, they can eventually wear out and weaken over time. A weak fuel pump may still pump fuel, but the vehicle may experience difficulty starting from the lack of pressure. A weakened fuel pump can cause the vehicle to take more cranks to start than normal, and in more serious cases may even cause the vehicle to require multiple turns of the key before it will start.

3. Engine Sputtering

One of the surest indicators of a faulty fuel pump is a sputtering engine — typically at high speeds. Should you be driving at a consistently high speed and the engine suddenly sputter before returning to normal operation, it may indicate issues within the fuel pump. In this case, the fuel pump cannot provide a constant stream of fuel to the engine at the ideal pressure.

4. Stalling at High Temperatures

Stalling can happen because of multiple problems within a vehicle but pay attention when it happens frequently at high temperatures shown on the car’s thermometer. A rising temperature paired with stalling often indicates a problem with the fuel pump motor. If stalling continues to occur with an increasing temperature gauge, it could indicate the fuel pump’s deterioration and need for replacement.

5. Loss of Power Under Stress

Another indication of a bad fuel pump is a loss of power when the vehicle is under stress — such as driving uphill or carrying a heavy load — or while accelerating. The engine shuts down because weakening parts of the fuel pump cannot keep up with the car’s heightened fuel demands in these situations. In these circumstances, the car will feel like it is unable to go or maintain the intended amount of power. If the fuel pump is the cause, it means it can no longer regulate fuel pressure accurately and provide the appropriate amount of fuel to the engine.

6. Car Surging

Irregular resistance inside the fuel pump motor may cause vehicle surging, and indicates a fuel pump in need of repair. Surging feels like the gas pedal has been used. However, it occurs at a random, consistent speed. If this happens often, it may be because of problems within the fuel pump.

7. Low Gas Mileage

If it seems like you’re filling up your car more than usual, it may be because of an issue within the fuel pump. A valve within the fuel pump may not be opening, causing more fuel than necessary to pour into the engine system. Excess fuel in the engine does not get stored or used.

8. Car Will Not Start

Another more serious symptom of an issue with the fuel pump is a no-start condition. If the fuel pump fails completely — to the point of not being able to provide enough fuel for the engine to run, the vehicle will refuse to start. The engine will still crank when the key is turned, but it will be unable to start due to the lack of fuel. A no-start situation can also be caused by a variety of other issues, so having the vehicle properly diagnosed is highly recommended.