Some 2007-09 Saturn Sky models with 2.0-liter turbo engines may produce a clicking and ticking sound from the engine compartment on cold startup. According to General Motors, the noise decreases in intensity and frequency as the engine warms, and is the result of the direct injection fuel system performing its normal functions.
Be aware that direct injection systems operate at extremely high pressures compared to conventional fuel injection systems. The rapid ticking noise that a car owner experiences on cold startup is due to the high-pressure mechanical fuel pump building the pressure needed to perform a cold start.
Once the engine warms, the requirements placed on the mechanical pump lessen, which in turn causes the ticking noise to decrease in intensity. The clicking sound that's heard on start-up is nothing more than the fuel injectors pulsing on and off under the high pressures from the mechanical pump.
Like the ticking sound, it also will decrease in intensity as the engine warms.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via email at [email protected].