My 2004 Buick Century is parked outside, it starts up fine and runs fine every morning and anytime it sits for a period over an hour in any kind of weather including minus 25 degrees. Sometimes when I shut it off for say 15 minutes or half hour and then go to start it again it will crank over fine but not start up. I can try several times, same thing…But then if I leave it alone for maybe another half hour and try it again it starts and runs fine. also no warning lights etc. It’s like something needs to reset itself. Do you have any idea what is causing this ?
Have someone connect a fuel pressure gauge to the fuel rail and check the residual fuel pressure.
If the residual fuel pressure drops to zero as soon as the fuel pump shuts off, the problem could be with vapor lock.
Tester
Vapor lock , possibility, my other thoughts are a fuel filter that needs to be changed or a failing fuel pump. Are there any other symptoms?
I’d guess that it’s electrical in nature. With a heat component.
When you initially shut an engine down, the temperature in the engine compartment rises as the heat internal to the engine dissipates via radiating out the sides of the engine and the exhaust manifold and header pipes release their heat outward. You no longer have the fan operating, the coolant circulating, or air passing over the engine, so the heat has no place to go. At some pint, the temperature begins to drop again as the heat entrapped in the engine compartment begins dissipating.
If you have any component adjacent to the engine, such as a coil pack, igniter, or crank position sensor becoming heat sensitive with age, it can fail when it’s heated beyond its operating norm and begin functioning again when the temp drops back down.