05 Passat TDI (AVB) - Strange noise after starting & leaking fuel after petrol purge

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Thu 24 Jan 2013 00:04
05 Passat TDI (AVB) - Strange noise after starting & leaking fuel after petrol purge - brianthnach

Hey guys,

Two weeks ago someone using my passat inadvertently put 20 litres of petrol into the tank. The car was not started. A mechanic was called who attempted to empty the tank of petrol.

However, his methods of doing this have left me somewhat baffled. I know that he disconnected both the supply and return fuel lines leaving the diesel filter going to the tandem pump and whether he attempted to draw fuel through the filter or back from the tandem pump I don't know. However he did say he was finding it difficult to suck the fuel through. Following this the pipes were mistakenly reconnected in the reverse order (tandem pump return line & tandem pump supply line swapped) and it was tried to start the car a couple of times. However they were then swapped back correctly and the car is going pretty ok now apart from some problems. The car was fully topped up with diesel to dilute any petrol remaining.

Ever since this happened there have been two issues.

1. Just when the engine is started there is a sort of grunting/dragging noise that lasts for about 3 seconds.It seems to come from the engine compartment.

2. When I return to the car in the morning I notice that it has leaked a noticable amount of diesel onto the pavement overnight. I have checked the filter area and it is dry of any fuel so I haven't been able to find where it is leaking the fuel yet.

I have ran VAG-COM diagnostics and no engine faults are showing. There also has been no noticable loss in power while driving.

I'd really like to get to the bottom of this and am really hoping that one of you more knowledgeable guys here can help me out with this.

Many thanks,

Jim

Edited by brianthnach on 24/01/2013 at 00:07

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Thu 24 Jan 2013 15:55
05 Passat TDI (AVB) - Strange noise after starting & leaking fuel after petrol purge - 659FBE

Jim, assistance in cases of mechanical abuse is always difficult - but a few suggestions.

The mis-connection of the fuel lines is potentially more damaging than the misfuelling. These engines are completely intolerant of poor maintenance or mis-handling.

You must as a first priority find the fuel leak. I would suggest taking a long hard look at the tandem pump which is driven from the free end of the camshaft. Access is difficult on the NS engine installations. Any leak here will also damage the coolant hoses below it, so prompt attention pays dividends.

This pump feeds the PD injectors with fuel at about 100 PSI. It would be a candidate for damage if the lines were interchanged. There is a pressure test point on the pump body which can be used to assess its condition. The pump may be responsible for the noises you have experienced.

There is further an electric lift pump in the tank. This could also be affected by the plumbing misadventure as there is a delivery valve fitted. The performance of the lift pump can be checked at the main fuel filter but diagnostic software will be needed to run the lift pump continuously without the engine running. You could, however hard wire the pump to make a check - access through a hatch in the boot floor.

Find the leak first - there may be a motorcylist following.

659.

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Thu 24 Jan 2013 17:06
05 Passat TDI (AVB) - Strange noise after starting & leaking fuel after petrol purge - Peter D

The noise may be air in the fuel system as you clearly have a leak. Contact the guy that drained the tank and find out where he disconnect the fuel lines. Regards Peter

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Thu 24 Jan 2013 17:08
05 Passat TDI (AVB) - Strange noise after starting & leaking fuel after petrol purge - jc2

And get him to fix it!!!!

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Fri 25 Jan 2013 03:16
05 Passat TDI (AVB) - Strange noise after starting & leaking fuel after petrol purge - brianthnach

hey guys,

Thanks very much for the sound advice 659, Peter & jc2. Its greatly appreciated. To be quiet honest I would go back to him with the car if I had indeed any faith in him to be able to repair it. Not being smart or fool hardy, but just the truth unfortunately. He would not have been on my call list in such a situation.

He disconnected both lines at the fuel filter (flow/return to tandem pump). The very fact that this was his method in light of the fact that the ignition wasn't even switched on with petrol in the tank sums up why I wouldn't have him repair the car.

I have put it in and removed the under tray to try and isolate the leak. So I will check first thing in the morning. However, first indication is that it is coming from close to the right front well.

Checked lift pump pressure at filter and it comes at 9-10psi. I also changed the fuel filter and did notice something unusual. There was a slight rattle coming from the control valve (Tee connection on top of filter). I took this out and at room temperature I could not blow air (in direction of arrow) to either the filter or the return pipe to the tank. Would this suggest a fault here?

I am hoping that it is indeed air in the system. I'll post back when I have a closer look tomorrow.

I appreciate all the help and advice,

Jim

Edited by brianthnach on 25/01/2013 at 03:17

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