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Got Gas? The Basics of Fuel Delivery Systems- Part 1

© Garth R. Smith

We all know what happens when you step on the accelerator pedal. The engine revs to a higher RPM thus propelling the car down the road at a higher rate of speed. But what feeds the gas to the engine? It's the fuel delivery system.

Years ago fuel delivery was handled primarily by the carburetor, sitting on top of the intake manifold and feeding measured amount of fuel and air through the intake to the different combustion chambers. There the fuel/air mixture was fired by a spark plug causing a small explosion which drove the piston down turning the crankshaft and providing engine torque. The carb was sort of like the human heart, the more power needed the more gas and air it provided to the engine. Carburetors are in use, but mostly on race cars or on older cars and trucks. They are rarely found on any new car being produced because they just aren't efficient at what they do. They only allow fuel to flow one way and any excess fuel not burned during the combustion stroke of the engine is sent out through the exhaust, increasing emissions and greatly decreasing fuel efficiency.

If you have a car equipped with a carburetor you may have a hard time finding parts to repair it or even someone who can fix it. I don't recommend that anyone attempt to repair their own carb unless they have a lot of time and patience and enjoy working on jigsaw puzzles with hundreds of small pieces. I've seen mechanics who have been turning wrenches for twenty years nearly have a stroke from the frustration of trying to rebuild a carb. If you really need to repair the old carb I'd recommend replacing it with a quality rebuilt unit. Ask your local parts store what they recommend. Try to find the one with the best warranty and keep in mind that cheaper is definately not better. These units are generally fairly easy to install, but be sure to remove all of the old base plate gasket material from the intake manifold or else you'll have an air leak that will draw air into the intake below the carb causing the car not to run correctly. Also make sure that all the hoses are reconnected to the new carb correctly or you could have a vacuum leak or a dangerous guel leak on your hands.

If you feel that you may be having a fuel related problem another part to examine befor condemning that old carb is the fuel pump. Most cars which are equipped with a carburetor have their fuel provided by a mecahnical fuel pump. This is generally located on the front of the engine and has an arm extending into the engine. This arm is moved by a rod connected to the crakshaft or camshaft in much the same way as an old fashioned hand operated water pump. This movement pumps gas from the tank and sends it through the fuel lines to the carburetor. Fuel pumps can commonly develop small fuel leaks and may also leak oil since they are lubricated by oil from the engine. If replaceing the fuel pump, again make sure that the old gasket is removed entirely or you can have a potentially dangerous fuel leak on your hands.