Focus taking a while to start up when warm?

[NotAGolf]

I've had a 58 plate focus for a few months. This last week I've had a problem where the engine takes 4-5s to start up, rather than the normal ~1s. Once it does tickover, it sounds and feels fine and it idles as normal

This only happens when I leave work at the end of the day. It's fine when I leave for work in the morning. It might be coincidence, but it's only started since we've had these few hot days in a row. If I stop on my way home from work (e.g. petrol/shops), it starts up fine then.

I've had a quick google and I've heard people blaming it on spark plugs, fuel filter and fuel pumps, but it seems odd that it's only a problem at certain times of the day. Any ideas? It's a 2.0 petrol if that makes a difference.

 

[Orionaut]

Fuel vaporisation can cause this, As can internal leakage in the fuel system.

(By Internal leakage I mean back leakage through the one way valve on the fuel feed and/or leakage via the pressure regulator on the return line. Neither are serious but both can cause the fuel pressure to drop while the vehicle is parked up. this means that you may have to crank for a few seconds to allow the pump to get the pressure back up to operating levels)

You can "Test" this by playing Diesel.

IE when you come to start the car, rather than cranking immediately, just turn the ignition on for a few seconds, then off for a few then on again, then off again then on and crank.

If you find that this eliminates the problem then it is a vaporisation/ fuel pressure problem. If not, perhaps it is something else but it costs nothing to try.

 

[NotAGolf]

Thanks Orionaut. I'm 100% sure caused by the heat now. Due to the traditional English weather it's taken a while for me to be able to know for sure. I'll try the technique you mentioned the next time we have a series of warm days.