When you turn the key in the ignition and your engine doesn't start, there are a few things that could be the culprit that you can troubleshoot in the fuel system of your Ford Focus before you take your car in to the shop. There have been numerous recalls on Ford Focus fuel pumps and fuel systems, so check with your local dealer with your VIN.
Troubleshoot the spark plugs in the fuel system of your Ford Focus first. The plugs are probably on the sides of the engine in models prior to 2000, and in the front and back of models made after 2000. The problem is either the engine lacking a spark or fuel. Pull out one of the spark plugs and connect it to a spark tester. Have someone turn on the engine, and if you see a spark in the gap, then there is a problem with the engine getting any fuel. If there is no spark, replace all of the spark plugs in the fuel system and try starting the vehicle again.
Check that your vehicle has enough gas, and that it is parked on a level surface. If the car is low on gas, the fuel injector could be sucking in air and not gas. Park the vehicle on level ground and add about 2 gallons of gas. Then try starting the vehicle again.
Check the fuel filter as you troubleshoot your fuel system. It is located underneath the rear of the Ford Focus, on the passenger side, near the gas tank. Remove the filter and replace it. Then, try to start the vehicle again.
Inspect all of the rubber hoses. Disconnect them, by loosening the bolts connecting them to one another, and squeeze each for soft or brittle spots. If any of these are present, replace the rubber fuel hose. Replacement hoses can be found at most automotive stores.
Remove the fuel line to check for blockage. It is located along the underside of the passenger's side of the Ford Focus. Place the line in a container and crank the engine. If no fuel comes out, have the fuel pump tested.
Consider the weather. If the temperature is below 30 degrees or over 80 degrees, there could be a temperature-related problem. For cold weather, you may need to add a de-icer to the gas tank. In hot weather, vapor lock can occur. In this case, pour cold water on the fuel pump and the lines.