Next time this happens, turn the ignition switch to "run" but do not crank the engine. After a few seconds, turn the switch off, then turn it on again. Do this a third time, then crank the engine. If it starts right up, suspect fuel pressure is bleeding off when it sits. That pressure should hold steady for weeks without running the engine.
Every time you turn the ignition switch on, the fuel pump will run for two seconds. After that two seconds, it won't run again until the engine is cranking. If pressure was bled off previously, it can't build up fast enough for starting when it's being bled off by the firing injectors. If this trick works, suspect a leaking injector or pressure regulator. A leaking injector might cause black smoke out the tail pipe immediately after start up.
Although not real common, a defective coolant temperature sensor could report a temperature that is warmer than the actual temperature. This will result in too little fuel being delivered during cranking. Your mechanic will connect a hand-held computer that will display the sensor readings. Also, the engine computer can put a diagnostic fault code into its memory if various sensors don't agree with each other. For example, the computer knows that if the engine has been off for more than eight hours, the coolant temperature sensor and the ambient air or battery temperature sensor should be reading exactly the same temperature. If they are not, the computer has a backup strategy to determine fuel metering during engine operation.
Monday, January 11th, 2010 AT 3:33 AM