Your description may be incorrect. I think you mean the engine cranks over as it should when you engage the starter (the engine turns over)but it doesn't catch. It sounds like the engine does not get ignition or fuel to enable the engine to run. If the engine cranks over the battery and starter are most likely OK. Keep in mind an engine must crank over sufficiantly fast enough for the engine to suport combustion and run. The engine needs three things to start, fuel (gasoline), ignition (spark) and mechanical integrity (it must develop compression in each cylinder to start ie mechanical components must be in synchronization with each other.Does the ignition fire at the time it is supposed to? The computer in your car takes in readings from sensors on the engine (like crank shaft position, camshaft position, engine coolant temperature, air temperature, volume of air being drawn into the engine, ect...) based on these inputs the computer in your car determines how much fuel to squirt into the engine and when to send spark to set fire to the fuel. If any engine sensor is giving an erroneous reading the computer does not make proper calculations and drvability issues occur. In most cases theses sensor values are needed to "turn on" the fuel pump. If the Check Engine/Service Engine Soon light is on there will be a code stored in the memory of the computer of your car that will indicate where the problem is or at least where to start looking. Even if the light is not on a professional grade scan tool attached to a 16 pin diagnostic socket under the dash of your car will be able to look at live sensor data so a mechanic can determine if sensor inputs to the computer in your car are correct and the computer outputs are correctly controlling fuel and spark. Using a scan tool to examine each sensor can eliminate have to to do intrusive testing at each sensor and also checks to a certain degree the integrity of the wiring harness of your car.
Check for fuel at the fuel injector or fuel rail when the engine won't start, then pull out one of the ignition coils and check for spark at the spark plug end of the ignition coil when the engine wont start. Next "listen" to the fuel injector. Using a mechanic's stethoscope (or use a long screw driver placing the handle end up to your ear place the metal tip end of the screwdriver against the body of the fuel injector), get a friend to crank over the engine while you "listen" to the fuel injector listen to each injector at the same point of the injector body. You should hear "click, click, click" as the injector is electrically opened and closed by the computer. If the injector is not being triggered you will not have fuel getting into the engine's cylinders. Disconnect the electrical connector at the fuel injector with the ignition key in the "on" position, (next position after the accessory position) you should have 12 volts at one of the two wires at the injector. This true for most vehicles but you need to consult a workshop manual for your vehicle to see that this is true for your vehicle. When the engine is running the second wire at the injector gets (triggered) grounded by the computer in your vehicle many times a second controlling exactly when and how much fuel gets injected into the engine. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online
All very good suggestions. I'll give them a go! Thanks!