Understanding the Fuel System in Your Car

August 23, 2011  

Learning about your car’s fuel system will help you understand and possibly troubleshoot fuel related problems. It can also help you speak intelligently to your mechanic about a Lynnwood Fuel System Repair. In the order that the fuel passes through the system:

Fuel Tank

The fuel tank is the container that hold the fuel (pumped at the gas station) until the engine “calls” for fuel. The tank has a float to indicate the level (Full, 1/2, Empty, etc.) that sends a message to the gauge in your dashboard. Also in the tank are baffles reduce sloshing around of the fuel while your vehicle is moving.

Fuel Pump

Usually located either inside or beside the fuel tank, the fuel is pumped to the fuel filter and injectors through the fuel lines. Older vehicles use a mechanical pump to transfer fuel to the carburetor. Cars with fuel injection, on the other hand, use electric pumps. Regardless the type pump, it must create enough pressure to provide distribution under any operating conditions.

Fuel Lines

All the components of the fuel system are connected by fuel lines. Usually made of steel or copper, the fuel lines are located away from the exhaust system (pipes, muffler, etc.) to prevent vapor lock from excessive heat. Vibration is minimized by securely attaching all fuel lines to the car’s frame and engine. Lines not secured properly can be damaged from excessive vibration during operation of your vehicle.

Fuel Filter

Positioned in the fuel line to clean water and particulates in the fuel. The fuel must be clear  to prevent the fuel injectors or the carburetor clogging. If the injectors or carburetor do become blocked, the fuel efficiency of your engine will be greatly reduced. In extreme cases, a completely plugged injector or carburetor will prevent fuel from reaching the combustion chamber in the engine.

Fuel Injectors

In newer cars (manufacture since the late 1980s), the carburetor has been replaced by the fuel injector. The injectors are located inside the manifold, so they can spray fuel into the intake valves. The quantity of fuel supplied is determined by the length of time the injector is open. Sensors are responsible for sending the signal to the injectors to open or close.


A mechanical fuel injection component, the carburetor was replaced as technology of the fuel system became too advanced for it to operate efficiently. Replaced by the electronic fuel injector, you will find carburetors only on older model cars.

When to Seek Professional Help

If you should notice a drop in fuel efficiency, it is definitely time to have your fuel system thoroughly inspect at Lynnwood Fuel System Service & Repair. The best way to track your car’s fuel usage is to:

  1. Start with a Full tank of fuel
  2. Set the trip meter on your odometer to “0” (zero) miles
  3. Once the fuel level drops to about 1/4 tank, re-fill the tank to Full
  4. Using the milage indicated on the trip meter zeroed out in Step 2, divide this by the number of gallons required to re-fill your gas tank to Full:
  5. This is a good estimate of the Miles per Gallon (MPG) to expect from your car
  6. Monitoring this efficiency with every fill-up will alert you to any drop immediately
Note: you need not use a Full tank to determine average fuel efficiency, just be certain to make note of the gallons purchased.
If you allow your gas tank to drop below 1/4 tank repeatedly, it can cause the fuel to foul.