Fuel Injection System

Parts of The Fuel Injection System 

• Fuel Tank 

  • Stores fuel until it is used 

  • Rest of the system can't happen if in bad condition 

• Filter 

  • Removes debris from fuel 

    • Solids and contamination 

  • Prevents clogging in injector, lines, and carburetor 

• Pump 

  • Takes fuel from the tank and passes it through the filter 

    • Two types 

      • Mechanical Fuel Pump 

        • Chain or belt connect motor off of engine to fuel pump  

      • Electric Fuel Pump  

        • Powered by electricity  

        • More reliable  

• Injector 

  • Takes fuel from filter and injects it into the carburetor 

    • Will be injected directly into engine when it is a diesel vehicle 

  • Powered by the pump—takes fuel from it 

  • Has a pressure regulator to control the pressure of the fluid 

• Carburetor 

  • Takes air from environment and mixed it with fuel 

  • Sends it to the combustion chamber 

    • Chamber will compress the mixture and ignite it to generate mechanical power 

• Fuel Lines 

  • Connecting tubes between each section of the Fuel Injection System 

  • Made of plastic or durable metal 

  • Located under car floor and in vulnerable places—places safe from engine exhaust, weather, road conditions, etc. 

• Fuel Gage 

  • Gage on dashboard that displays quantity in fuel tank 

    • Traditional vehicles did not have a gage 

• Fuel Gage Sending Unit 

  • The unit that controls sending of the data to the gage 

  • Most precise between ¼ and ¾ tank 

• Emission Vapor Controls 

  • Works with fuel return lines 

  • Prevents fuel vapors from being discharged into ambient air 

    • If faulty, can result int: 

      • Gasoline odors within vehicle 

      • Roaring when the gasoline fumes ignite 

        • Generally bad for the environment 

• Fuel Pressure Regulator 

  • Maintains the pressure within the fuel system 

  • More commonly used in the fuel injectors because they generate more pressure than carburetors 

Types of Fuel Systems 

1. Single-Point System 

   1. Most known system and also referred to as the Throttle Body Injection System 

   2. Carburetor is attached with two fuel injectors in a throttle body* 

   3. Were invented as a good alternative for simple carburetors 

   4. Easy design with low maintenance and repair requirements  

   5. Less efficient and less precise than multi-point 

2. Multi-Point System 

   1. Most commonly used injection system 

   2. Has separate injector nozzles for each cylinder 

      1. When engine idles, fuel remains in an orifice for more than 148 milliseconds, which reduces efficiency when compared to SPFI 

   3. Located outside of air intake—also known as a port injection system* 

   4. Regulates fuel more efficiently, more precise, and reduces chances of fuel shortening in the manifold 

   5. Requires more maintenance, higher repair costs, and as a complex design 

3. Sequential Port Fuel Injection (SPFI) System 

   1. Also known as Timed Fuel Injection System or Sequential Fuel Injection System 

   2. Nozzles do not inject simultaneously, only according to the corresponding cylinder requirements  

   3. Inject fuel just before opening of inlet valve 

      1. Fuel doesn’t stay long, which increases efficiency and reduces emissions rate 

   4. More efficient ad precise than multi-point 

4. Direct Injection System  

   1. Most simple and innovate injection system 

   2. Injects fuel directly into combustion chamber after opening valves 

   3. Most common in diesel engines, but becoming popular in petrol engines 

*Terms 

Throttle Body- 

Device that controls the amount of air entering the engine 

Port Injection System- 

Pre-mix fuel and air inside the manifold, then sends it to the cylinders