My car is a 98 Quest, which, since bought @ 85000 miles, has always started promptly (2 or 3 turnovers of engine). About 4 months ago, mileage 135000, the car began this pattern: Prompt start first thing in the morning. If turned off and then restarted after l/2 hour, prompt start. If instead restarted after 5 hours or so, car requires 15 to 20 turnovers of engine. If instead car is restarted after 8 hours or more, car starts promptly. Since this behavior began line fuel filter has been replaced and so has ignition module. When gas cap is removed there is always a whoosh. No “service engine” light has ever appeared, and no codes have shown up. The battery is in very good condition and turns the engine over rapidly. The car runs very well and is as peppy as it was before this pattern began.
Have you ever changed your fuel filter or had your fuel injectors cleaned?
The good news, it starts after 15 turns, I don’t know how many seconds you are talking but long cranking is pretty hard on starter motors. At the 5 hour point if it is that reliable start checking things, spark detector as rocketman said in another thread is $15, Is the woosh associated to the onset of the problem? Intermittent problems are the worst. We had a van that every now and then would not start, no error codes, once it sat for an hour it would start fine. Had my wife get in the habit of stopping at the dealer and turn it off and see if it would start, as by the time it got towed to the dealer (twice) it started fine. It pulled it’s little symptom at the dealer, they checked it right away and ended up replacing the fuel pump to solve the problem.