It is difficult to say what makes certain drivers take such perverse pleasure in watching others try unsuccessfully to start their cars; perhaps it’s the idea of emotional fidelity on an automotive level. Regardless, it doesn’t take a loving touch to get any fuel-injected engine or carburettor moving – just an awareness of what you need and what mood you’re in at the moment.
To start the engine
Starting an engine requires slightly different criteria than keeping it running, especially when the engine is cold. Compressing the air and fuel by squeezing it with a piston causes it to heat up, bringing it closer to its autoignition point and making it easier to ignite. Engines work best when they are hot, because they are designed that way; compression ratios, air / fuel ratios, and ignition timing work under the assumption that there is some heat present on the cylinder walls and pistons. Without that heat, the engine needs a denser fuel cloud to sustain combustion.
Engines with carburettors
Carburettors are basically measured fuel leaks, which use a vacuum on the engine to suck fuel through valves on the carburetor and into the engine. The engine vacuum comes out of the pistons dropping into the cylinders and, like air pressure, takes time to build. The engine will not draw fuel through the carburetor injectors until sufficient vacuum builds up, which is part of the reason why carburettors often have a mechanical fuel spout (known as a “power valve”) to supply fuel. request. Rapidly striking the gas pedal engages the power valve and splashes fuel into the inlet manifold (combined with the throttle plate,
Starting a carbureted engine
For carbureted engines that use a choke, the best procedure is to close the choke, pump the gasoline a few times to splash fuel in, and then flush the gasoline until it reaches the engine. The choke controls the flow of air, so dumping the gasoline will only open the carburetor fuel valves and allow the vacuum to draw fuel much faster. Starting an engine without a choke requires a bit more fuel (usually an extra pump or two) and putting your foot more lightly on the accelerator. Open the throttle plates too far and the mixture will come out, stopping the engine.
Fuel injection engines
Fuel injection engines work a little differently. A fuel-injected computer knows the engine is cold, and adjusts the air / fuel ratio to compensate. Instead of a choke plate, most injection engines close the air control valve at idle to reduce air flow to the engine. When you turn the key on a cold fuel injected engine, the IAC valve closes and the computer injects a little more fuel to encourage ignition. Most injection computers will also delay the timing a bit, since too much advance makes the engine more difficult to start.
Starting a fuel-injected engine
If you’re one of those old-fashioned people with a tendency to pump gasoline before starting a fuel-injected engine, welcome to the Senior Club. Pumping the gas pedal on an injection engine will do nothing apart from opening and closing the throttle blades; Finally, the IAC and the computer determine the fuel ratio. Keeping the throttle open increases airflow in the engine, which actually makes it harder to start.
