Audi A5 3.0 TDI Starting Issues - CAP Engine

Hello everyone!

I have an Audi A5, manufactured in 2007, with a 3.0 TDI engine, license plate code CAP, that occasionally has trouble starting. This means it sometimes cranks for approximately 1-4 seconds before it actually starts, and this has been happening since I've owned the car, about 1.5 years.

This issue occurs approximately every 10th to 30th time I start the engine. Otherwise, it starts normally, and in both cases, it runs smoothly without any jerking, black smoke, or other problems.

It doesn't matter if the outside temperature is +25°C or -10°C; it can happen at any time.

I had the error memory read out, but it didn't show any relevant information regarding the issue, such as the glow plug system, glow plugs, fuel rail pressure, or anything else.

Just for the record: The intake manifold flaps and EGR valve have already been replaced, and the engine software has also been optimized, but that didn't make a difference (those were not replaced or changed due to the starting problem).

I've found a few articles online about this problem, but I haven't found a solution anywhere.

Does anyone here know anything about this, or can anyone suggest an approach to solving it?

Thank you very much, Martin!

Hi,

Without a diagnostic system, you will have a very difficult time determining the cause. Moreover, the problem doesn't seem to be causing much distress...

Best regards, Rainer.

Hello Rainer!

Okay, thanks. Without a diagnostic system, it might be difficult. However, I only have the old VAG-Com, which doesn't work with the CAN bus anymore. I should probably get something new.

However, this problem is already somewhat annoying. The starter motor, flywheel, and battery are unnecessarily stressed when the engine has to "crank" for a longer time before starting. And if the problem can be easily fixed, I would fix it.

"I was thinking it might be similar to some of the "pump-injector" systems where the injectors don't inject enough fuel during startup, which makes them difficult to start. This can often be solved with a software update. Alternatively, it could be a sensor or a component that's causing the injectors to inject too little fuel."
Perhaps someone is familiar with this problem?

Hi Martin!

Quote:

Or it could be a sensor or a transducer that is causing the injectors to inject too little fuel.

You could use VCDS or KOBD2Check to check if the engine control unit is seeing a plausible coolant temperature reading.

Okay, thanks. I'll see if I can find anything out using VCDS, and I'll let you know if I have any success.

Hi Martin!