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J&W Auto Repair

AUTOMOTIVE: Fuel injection and fuel control

By Wyatt Nettles, J&W Repair

Think back to the carburetor days. The carburetor was what delivered the fuel to the engine. This worked for years. When we first went to computer-controlled engines, the fuel was controlled by solenoids that controlled fuel through the jets – did not work well. Those days are gone, thank goodness!

Fuel injection is the way to go and is easier to control. Putting the correct amount of fuel to an engine helps fuel economy and how long an engine will last.

Computers control fuel delivery by using fuel pressure regulators, temp sensors, manifold air pressure sensors, oxygen sensors, throttle position sensors and electronic-controlled injector. Temp sensor air and coolant tells the computer the temp of the engine and air coming into the engine. The colder the engine is, the more fuel it needs to run properly. Like carburetors used a choke to provide more fuel, the computer provides more fuel when the engine is cold. Computers will add or takeaway fuel according to these temps.

Map or mass air flow sensors tell the computer how much air is going into the engine with a reading from the throttle position sensor. Fuel pressure regulator controls fuel pressure and keeps pressure at the correct pressure under different fuel rates. Oxygen sensors tell the computer the amount of oxygen in the exhaust. This allows the computer to control fuel to keep it at a good air/fuel ratio of 14.7 to 1. The computer takes the information from sensors and then controls the injectors to provide the proper amount of fuel.