I'm an idiot.... help needed

alexander555

New Member
Arriving home earlier today in the A8 TDI (D3) and it was almost like it started misfiring.

After scratching my head for a while and making a couple of tea I just realised I've gone and put petrol in it! My excuse is I didn't sleep well plus I have a few classics and my brain was on an automatic car = petrol, truck = diesel mode. But yeah this is very embarassing and has dented my ability to troll other people that do this.

I'm pretty capable of fixing my classics, but not very clued up on these more modern TDI engines. I'm guessing my biggest issue is that the petrol won't have been lubricating the fuel pump etc. and associated risk of crap getting into the injectors. I am hoping that if I get the petrol out and put a load of diesel in it will clean itself out.

I have a siphon so emptying the tank shouldn't be too hard. I was thinking I should order a new fuel filter too. Am I right in thinking the fuel filter is under the vehicle towards the front? I can disconnect that older filter and blow some compressed air into the tank to clean out that end? What about from the the fuel filter into the engine, can I do anything? I'm a bit lost on this engine and I don't have a technical manual. So basically questions are:

- Siphoning the tank should be okay, any watchouts?
- Remove and replace fuel filter, any suggestions?
- How to deal with the petrol that's between the filter and the injectors, can I do anything?

How worried should I be? The car was the low fuel warning with diesel and I put 40 quid worth of petrol in, it only started misfiring about 1km before I stopped driving.

Appreciate any help.
 

NHN

Retrofitter - Audi - VW - Skoda - Seat
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VCDS Map User
Oops, well fuel filter, pop the rear seats up & siphon from the tanks each side, pull the pumps out & drain them, maybe blow air down the fuel lines from the bay to make sure they're empty, guess then take the risk it's not damaged anything internally, upto you how far you go.
 

alexander555

New Member
Oops, well fuel filter, pop the rear seats up & siphon from the tanks each side, pull the pumps out & drain them, maybe blow air down the fuel lines from the bay to make sure they're empty, guess then take the risk it's not damaged anything internally, upto you how far you go.
So I went ahead and did it yesterday and the car was running fine again immediately. What I did was siphon the tank. I used VCDS and the fuel pump to get it properly empty, I think it’s the only way as I realised it’s a saddle tank. I then disconnected the return and feed under the bonnet and used my compressor to empty all the lines. After all that put fresh diesel in and it started after just 5 seconds or so. So definitely hasn’t been as bad as I worried about. I hope and doubt the petrol was in long enough to degrade any rubbers or seals and I’m trying to be positive thinking it’s given the system a good clean hahaha
 
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