starting problems

An engine needs three basic things to start, mechanical integrity (the engine's components must be in synchronization with each other and the engine must be able to develop compression), the engine must get fuel injected into the cylinders (fuel must be injected into the engine ( there is a computer that takes inputs from many sensors on the engine, interprets these signals and decides when and how much fuel to inject into each cylinder) finally the engine needs spark to ignite the fuel injected into the engine, (the spark is also controlled by the vehicle's computer deciding when the spark arrive at the spark plug). If any engine sensor has failed (crank angle sensor, camshaft position sensor, intake manifold pressure senor/air flow meter, coolant temperature sensor) any of these will cause the engine to fail to start by causing a loss of spark or fuel delivery. All these components need electricity to function, a failed fuse, relay, open or shorted electrical circuit could cause the computer, fuel pump or ignition system not to function. Unfortunately there are too many things that could cause your engine not to start to be able to pin point anything to specifically look for. Check for fuel and spark first but it is quite likely your engine may have a blown head gasket from its overheating episode. The most accurate way to test for a blown head gasket on a gasoline engine is to test for the presence of carbon monoxide in the cooling system. Snap-On, Matco (part # CO 2000), and Napa sell a tool to check to carry out this test. Another link to a supplier of this tool is http://www.etoolcart.com/combustion-leak-detector-lis75500.aspx. Carbon Monoxide is only present if there is a blown head gasket or cracked cylinder head. http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm I think the napa part number 700-1006. http://www.blockchek.com/instructions.htm . Signs of a blown head gasket are coolant loss (frequently have to top up the coolant level of the engine without seeing an obvious leak), experiencing over heating or rough engine running or the presence of white sweet smelling steam from the exhaust. A badly blown head gasket may allow engine coolant and oil to mix. Get it checked out even if it starts as you may end up doing more damage if this problem is left unattended.