Skip the auto shop - Our mechanics make house calls

How Does Fuel Injection Work?

fuel injection

When it comes to engine performance, there are few things more important than fuel delivery. All of the air you can forcefully induce into the cylinders will do nothing without an appropriate amount of fuel to burn. As engines evolved throughout the twentieth century, there came a point where carburetors became the weakest link in the drivetrain in terms of efficiency and dependability. Fuel injection has since become a standard feature in every new vehicle.

Fuel injectors atomize gas, allowing for more even and consistent ignition in the combustion chamber. Unlike carburetors, which rely on the vacuum created by the engine to draw fuel into the cylinders, fuel injection systems precisely deliver a consistent volume of fuel. Modern cars use electronic fuel injection systems that are controlled by the ECU.

The rise of fuel injection was as predictable as the rise in popularity of cars themselves. At the turn of 20th century, it was incredible for a vehicle to travel 60 miles per hour. By the turn of the 21st century, people were groaning at traffic traveling only 60 miles per hour on the highway. Cars today are more dependable and more accommodating to creature comforts and occupant safety than anyone could have imagined a century ago.

What did fuel injection replace?

Fuel injection systems were offered as an upgrade from carburetors when they first came out, and they remained in that role until the 1980s when they started becoming standard equipment on every new vehicle. Fuel injection offers a number of advantages over carburetion, but it was ultimately production cost that killed the carburetor.

For quite a while, carburetors were the simplest and cheapest way for car manufacturers to deliver fuel into the cylinders of their engines. A series of oil shortages in the 1970s forced the government to regulate vehicle fuel economy. Once manufacturers were required to develop more efficient carburetor designs and manufacture more complex parts, the cost of producing carbureted vehicles was great enough that fuel injection became the more cost-effective solution.

For consumers, this was actually great news. Fuel injected vehicles drive more consistently and required servicing and tuning significantly less often. Emissions are easier to control as well, and fuel economy is boosted with more efficient fuel delivery. There are a number of different fuel injection systems out there, but they can all be sorted into two categories: mechanical fuel injection and electronic fuel injection.

Electronic fuel injection (EFI)

Electronic fuel injection allows for extremely precise control over how much fuel is sprayed into the cylinders. It follows a fairly straightforward process to do so:

  1. The fuel exits the fuel tank via the fuel pump. It travels through fuel lines towards the engine.

  2. The fuel pressure regulator constricts the flow of fuel and only lets a calculated amount through to the injectors.

  3. The fuel pressure regulator knows how much fuel to let through to the injectors via a signal from the mass airflow sensor (MAF). This sensor tracks how much air is entering the engine at any given time. The overall volume of air entering the engine along with the optimal air/fuel ratio decided by the manufacturer gives the electronic control unit (ECU) enough information to calculate the exact amount of fuel the engine needs.

  4. The fuel injectors themselves open to let the atomized gas directly into the combustion chamber or into a throttle body.

Mechanical fuel injection

Mechanical fuel injection was developed before EFI and paved the way for EFI technology to be developed. The main difference between the two systems is that mechanical fuel injection systems use mechanical devices to meter the correct amount of fuel into the engine. These systems have to be tuned for optimal performance, like carburetors, but also deliver fuel via injectors.

Aside from being more precise, these systems weren’t a massive departure from their carburetor counterparts. They were, however, extremely useful for aircraft engines. Carburetors do not work well against gravity. To deal with the g-forces dealt out by aircraft, fuel injection was developed. Without fuel injection, fuel starvation would have stalled many aircraft engines during tricky maneuvers.

Fuel injection of the future

Going forward, fuel injection will become more and more precise and offer increasing efficiency and safety. Each year engines have more horsepower and produce less waste per horsepower.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Find the Keyless Code on a Ford Explorer or Mercury Mountaineer
Many Ford Explorers and Mercury Mountaineers were manufactured with an option known as the Ford keyless entry keypad. Some models refer to it as SecuriCode as well. It...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...


Related questions

Q: Gas gauge is not working correctly

If the gauge pointer on the fuel gauge is registering incorrectly, or fluctuating excessively (it can move a little depending on vehicle angle and motion), there could be a problem with the sending unit in the gas tank, the dash...

Q: Gas

Hello, thank you for writing in. You would be surprised how often putting the wrong fluids in a vehicle happens, and how much damage it can do to the engine. Fortunately you are in a situation where it does not...

Q: After multiple replacements, gas mileage is worse - 1997 Ford Aspire

The fuel economy will change depending on the whether the transmission is manual or automatic. According to fueleconomy.gov the manual transmission Ford Aspire is getting a combined 33mpg while the automatic get 26mpg. Ford's initial adverts were 34 mpg city...