when my car's engine is cold, it turning on immediately. But when it is warm an turn it off, then after 20 or 30 minutes need long start for turning on. where is problem? my car is peugeot 405 made in 2001 with magnet mailer ecu. I replace the rpm sensor but nothing changed.
It sounds like the car is unable to maintain sufficient pressure in the fuel rail.
Have a look at this answer for more details on potential causes for hot start problems.
The reason why this happens only for hot starts is because the fuel is more likely to vaporize as temperature increases. In order to avoid vaporization problems the fuel lines are expected to be pressurized during a hot start.
The rpm sensor was a good candidate.
I would consider the following tests:
- Start it warm with opened fuel filler flap.
- Clean the contacts of every temperature sensor and the crankshaft position sensor (Plugging them out and in several times).
- Does the exhaust fume smells like petrol? (Attention: Health hazard!).
- Spray start-pilot while starting the engine. Does the engine start?
- Are the spark plugs wet afterwards? Could you post photos of your spark plugs?
There is not enough information as others have indicated, however, the most likely cause is that the vehicle has a bad sensor that is telling the computer that the engine is warm when it is not so it doesn't enrich the mixture sufficiently. No choke is used on these cars.
If the car is real old '70s or before, the mechanical choke would cause this type of problem because it would stay hot while the engine needed more choking to start. Or the choke would stick. This is for info only - this vehicle is a 2001.