1.7 2006 Astravan very difficult to start

Hi all,

I'm having an extremely hard time trying to start my 2006 1.7l diesel astravan. There may be a few reasons for this;

- before Christmas, I accidentally put around 4 liters of petrol into it when it was empty, topped it up with diesel and drove on - seemed fine.

- secondly, I had the timing belt changed. I can't see any reason why that would affect the starting.

- After that, I gave it a full service including a new fuel filter which was extremely hard to prime and required a lot of cranking to start it but once started it was fine.

All this happened over a period of about one week including the petrol accident.

After putting the petrol into it and after giving it a service it began to get slower to start and then it just got worse and worse. Now a few months on, it takes about 10 -15 secs cranking but it always starts.

I'm hearing very very strange sounds coming from the fuel tank like a gurgling sound when I'm sitting in traffic or just ticking over - hot or cold. It sounds like someone blowing with a straw into a glass of water (if you know what I mean....) I find that it's slightly easier to start if I park it facing down a hill.

I've had the injectors checked and they're fine. I've had a fuel pressure sensor changed with no difference. I also dropped the fuel tank and had it cleaned out still with no difference.

I changed all the glow plugs and the relay but they're all working properly.

If anyone has an idea what might be causing I would really appreciate your suggestions.

Thank you.