Petrol fumes from THP engine

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Re: Petrol fumes from THP engine

Post by white exec »

Could you get yours pressure tested?

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

The A/C system has been ruled-out as the culprit as the fumes do not appear in the cabin when the A/C is set to recirculation mode. It is also fairly clear that the fumes are petrol, not A/C gas/oil.

It appears that the leak is getting steadily worse, so at some point the location must become obvious.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

I had another look at this today, and noticed (the bleedin obvious) that the low pressure fuel line is damaged:
308-fuel_line.jpg
I can't actually detect any fuel coming from the visible split, but it is in the general area, and I can't find a leak anywhere else...

I don't know whether this is a single or double wall pipe, and I don't know if it is practical to fit a new length of hose to the fittings, or whether to take a deep breath and find a proper replacement.

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Re: Petrol fumes from THP engine

Post by RichardW »

If in doubt always look for the obvious!

Appears to come as a pair, not clear from your pic whether it's the short bit across the engine, or the long bit from the tank, neither are too expensive (well, in the UK anyway!)
fuelpipes.JPG
fuelprices.JPG

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

It is the short pair that run behind the engine.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

I have again had the manifold off to find the fuel leak, and I am fairly sure that the low pressure pipe, although visibly damaged is not the source of the leak.

Firstly I wrapped the damaged section of pipe with some wide plastic conformal tape, not because I expected it to hold in 5 bar of pressure, but because any leak would find a way around the tape and make itself more obvious. It hasn't.

Secondly, I repeatedly find that the petrol fumes can only be detected after the engine has been cranked (not just by switching on the ignition), which points to the high pressure fuel pump or high pressure feed pipe, or the injection rail or injector seals.

Ordinarily I would just pull the injectors and throw on a new set of seals at this point, but it is not a cheap or easy excercise on this engine. Fistly if the injectors are disturbed, you need to fit a hew high pressure feed pipe and a new set of seals (and they are expensive for a set of 4). Then you need a special mandril and a sizing tool to fit the new Teflon seals to the injectors and injectors into the head. It looks like about £400 of parts and tools as soon as you touch it.

Backtracking a little, the PSA procedure for finding leaks around the high pressure fuel system involves the use of a leak detector product that is sprayed onto the various sels and unions. Does anyone know the commercial name of this product?

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Re: Petrol fumes from THP engine

Post by white exec »

Nothing listed under Products for Professionals on servicebox, except AC and radiator items.

LiquiMoly #3350, Leak Detector Spray, maybe?

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

white exec wrote:
17 Feb 2020, 12:23
Nothing listed under Products for Professionals on servicebox, except AC and radiator items.

LiquiMoly #3350, Leak Detector Spray, maybe?
I don't think that that is the stuff. Liqui Moly 3350 is a detergent spray that creates bubbles at gas leaks, I don't think that it would work for petrol.

PSA don't even seem to give a part number to the stuff they recommend. Maybe it is vapourware?

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Re: Petrol fumes from THP engine

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Re: Petrol fumes from THP engine

Post by white exec »

Looks more like it. Says the 25ml bottle treats 8-10 lit of petrol, so a near-empty tank needed.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

No, the PSA procedure clearly shows an aerosol spray product being used, and does not mention a UV light. I have not found any BMW reference to leak detection procedure for these.

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

RichardW wrote:
17 Feb 2020, 19:39
Somehing like this? https://www.amazon.co.uk/Torch-Detectio ... B00TU9BHN6
I have ordered one of those kits anyway, but it will take a couple of weeks to arrive here.

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Re: Petrol fumes from THP engine

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Message Wheeler - he might know as he is a PSA tech.

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Re: Petrol fumes from THP engine

Post by GiveMeABreak »

This isn't an aerosol but is for the job:

https://www.amazon.co.uk/Torch-Detectio ... B00TU9BHN6

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Re: Petrol fumes from THP engine

Post by xantia_v6 »

The florescent dye arrived, and when the tank was almost empty, I put a small dose into the fuel tank and ran the car for about 10km.

The result is somewhat inconclusive. There is no sign of the dye on any part of the fuel system that can be seen from above (even with the air ducting and inlet manifold removed). I have not yet looked from underneath.

There do however seem to be traces of dye on the inside of the intake air ducting and tracing back, it is coming via the PCV system from the engine oil. I did not check for the presence of florescent dye in the engine oil before I added to the fuel tank, but can't think of a reason that the engine oil would have dye of the same (orange) colour.

If we assume that the dye came from the petrol, then I can only think of 2 plausible paths:
1. From the high pressure fuel pump through a leaking shaft seal.
2. Direct from the combustion chambers past the piston rings.

I don't like the expense of the first option, but I don't really believe the second, given that the engine is still running perfectly*.

* Last night when I wasn't in the car, it apparently flashed up an error code on the dashboard for a pressure fault. Diagbox however could not find any fault which would seem to correspond to this (the car does not have tyre pressure monitoring fitted). The only engine fault codes present were for "superknock" about 100 km earlier, which I noticed at the time.