I've had similar/same on a ford focus. Not starting when hot but no loss
in performance when running.
With the radio off and in a quietlocation and when cold on the first
turn of the key, before cranking the engine on the starter, you should
be able to hear the fuel system priming for a second - you should be
able to hear the fuel pump starting.
When hot do you hear the same fuel priming sequence?
In my cases when the car wasn't going to start I couldn't hear the the
fuel priming.
In my case when it happened for the first time replacing the crank case
sensor cured the problem for around for 18+ months. At first it was only
occasionally that it wouldn't start but over a short period the problem
became more persistent.
The second time it happened it was the fuel pump that had failed and the
cost was approx £250 all in to fix (small independent back street
garage). The fuel pump is fitted to the petrol tank which needs to be
removed to repalce the pump. In this case the car wouldn't start 75% of
the time when hot.
Both times when hot and wouldn't start sometimes the temperature gauge
would go to full scale even though the car had been sitting for 30
minutes. The temperature gauge would then slowly drop to zero scale.
The temperature sensor wasn't the cause of the problem.
With the crank case sensor fault the car would always start when the
temperature read zero. With the fuel pump fault it was a lot more
problematic but the car would always start when left overnight or left
in the works car park all day and usually when left to cool down for 2
hours.
The link below gives a description of the start up sequence and why the
crank case sensor could have been a prime suspect
http://preview.tinyurl.com/mtu87y9
scroll down to the article with the lengthy start up description.
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