Audi A3 8P 2009, 1.4 TFSI – issue description:

Only on hot, sunny days, the car has problems starting or it stalls immediately after starting.

Fault codes:

• 1177:004 – Engine control unit – no communication

• 0819:009 – Fuel high-pressure sensor – open circuit / short to ground

On cloudy or just warm days, the car runs and starts perfectly fine. The issue only occurs in extreme heat and direct sunlight, when the car gets very hot inside.

The car has already been to three different mechanics:

• Ignition switch connector replaced

• Crankshaft and camshaft position sensors replaced

Other mechanics could not diagnose it because the problem is intermittent and only happens during hot sunny weather, making it hard to test on site.

I am looking for help or advice on what could cause such a temperature-dependent electrical issue.

 

I'm from Poland, need to help - cheers

 

All I can think of as a temperature dependent cause is vapourisation of the fuel in the pipe from the tank. That implies that either the low pressure pump or the high pressure pump is faulty.

Welcome Oskar,

I would think there should be a coolant temperature sensor on it, which signals the correct mixture to the ECU dependent on coolant temperature. Affected by ambient? 
Does it smell of excess petrol when it does start? 
You could try E5 rather than E10.

Regards,

Gareth. 

8 hours ago, Magnet said:

Welcome Oskar,

I would think there should be a coolant temperature sensor on it, which signals the correct mixture to the ECU dependent on coolant temperature. Affected by ambient? 
Does it smell of excess petrol when it does start? 
You could try E5 rather than E10.

Regards,

Gareth. 

Yes it smell petrol after start, What it mens?

It means that the fuel mixture is too rich for the temperature.

52 minutes ago, Magnet said:

Oznacza to, że mieszanka paliwowa jest zbyt bogata w stosunku do temperatury.

Hi Gareth, do I need to replace high pressure pump or sensor? 

Thanks for your time. 

I think you now need more sophisticated diagnostics since it would be difficult to say whether it’s the coolant  temperature sensor is signalling incorrect readings to the ECU, or whether the ECU is at fault. 
Regards,

Gareth.