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Thread: Petrol in oil - next steps?

  1. #1
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    Petrol in oil - next steps?

    I upgraded my HPFP with an Autotech kit about a month ago. Last week I started to get a strong smell of petrol in the cabin; checked the dipstick and it smells more like petrol than oil. A bit of Googling suggests I probably damaged the internal seals in the HPFP when I put the Autotech bits in, and the pump's been leaking petrol into the crankcase.

    I've already got a new HPFP on order, and I've parked the car until I can replace the pump and the cam follower. My question is what to do about the oil that's in the car? Should I run an engine flush (some of the Liqui-Moly stuff) using the oil/fuel mix that's in there now, or just drain it and refill? My thinking at the moment is to just drain it straight away and refill it, then change the oil again in about 1000kms. I don't think I've done any lasting damage to the engine - it runs fine, and I think it had only been leaking for a few days before I caught it - but want to make sure I don't make it worse if I can avoid it... all advice appreciated.

    Bonus question: for anyone who's got experience with HPFPs, is the upgraded pump meant to be more a preventative maintenance/safety thing or a performance thing? I'm running a Superchips stage 3 tune, and Superchips have told me I shouldn't need an upgraded pump (the tune requires a K04 and Golf R injectors, but doesn't say anything about an upgraded HPFP). I bought the upgrade kit because I'd misdiagnosed another problem as a fuel delivery issue, and the car always seemed to run fine with the standard pump - kind of hesitant about going down the upgrade route again after this experience.

  2. #2
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    The upgraded HPFP includes a larger piston so that it can flow more fuel - so its an upgrade as such. From memory i believe it allows the HPFP to flow around 40% more fuel. I installed the Autotech HPFP upgrade on my Golf R (and did a comprehensive DIY) and never had an issue, so either your pump was worn or perhaps you have pinched one of the o rings and this is causing the leak.

    Autotech HPFP Upgrade full DIY guide with pics

    As for the fuel in your sump, personally i would drain it and refill with just some cheapish oil and run that for a day or two. Then flush again and refill with your normal oil. The engine flush products that you add to the oil, and let the engine run for 10-15 mins before draining are designed to remove sludge and gum/varnish from oil galleries etc - personally i think a flush product would be useless in this situation.
    Last edited by Lucas_R; 27-05-2019 at 03:20 PM.
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  3. #3
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    Thanks for the advice - actually followed your DIY when I installed it! I think the pump I rebuilt might have been worn - it came off a Golf R with ~30,000kms - but I'll try running a stock pump for a while anyway and see how well it works. I assume the rebuild kit is still fine even if the pump is wrecked, so might get someone with a bit more skill to install it in another HPFP one day...

    That makes sense re the oil change - will get this done ASAP and report back

  4. #4
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    Vw Kombis while not as high tech as the golf could suffer fuel in oil if a fuel pump was installed with out a a check valve. Totally different scenario to yours but the end result was the same.
    If the Kombi was parked on a slope (nose up) the fuel would not only fill the sump but the cylinders and exhaust system.

    Draining the oil and replace the oil filter will be sufficient the residual fuel will evaporate out pretty quickly - while your waiting for the new pump leave the oil filler cap of to allow the fuel vapor out. Anything that’s left when the engine warms up will evaporate out and be sucked back in through the PCV system and burnt.

  5. #5
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    Cheers for the advice! Quick update: I've replaced the HPFP with a stock one and drained/refilled with cheap 10w40 and a new oil filter. I've run it for about 30kms and I can definitely still smell petrol on the dipstick and through the air vents (but less than before) - will drain and refill with better oil in a couple of days, and hope that the smell goes away after that. I've replaced the PCV valve with a catch can - I guess that makes it less likely that all the petrol residue will get burnt off?

    I did notice a *lot* of crud in my catch can when changing my oil, so will probably run an engine flush just to be safe - not sure if it'll do anything about the petrol residue, but I figure it can't hurt. FWIW, I think the smell coming through the air vents is stronger at idle? I'm 90% sure the problem was with the HPFP, but is there any other obvious reason I'm missing why I might be getting fuel in my oil (other than damaged piston rings)?

  6. #6
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    An injector that's stuck open is the only other possible source really - but if you had recently played with the HPFP then its likely the HPFP is the issue.
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  7. #7
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    Is your catch can vented to atmosphere or still a closed circuit like OEM? If its vent to atmosphere, or if not and has a leak anywhere in that system then that could account for the smell. If the catch can represent a big flow restriction then the pre turbo intake vacuum may not be pulling blowby like it should. That coupled with a PCV system leak could cause the stink.
    I'm just thinking along the lines of is it a petrol smell or is it a blowby smell? Was there actual petrol in the oil ie was it really thin?

  8. #8
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    The catch can isn't vented - but something in this system was also my first thought when I first caught the smell, along with lines from the carbon canister. The oil I drained doesn't seem too thin; the thing that leads me to assume there's petrol in the oil (aside from the fact that I've just been messing with my HPFP) is that the dipstick smells more like petrol than oil.

    Also - in trying to trace the source of the smell last night, I took the dipstick out and stuck my nose in the dipstick hole, and there was a really strong petrol smell coming out of the sump. I couldn't smell it anywhere else in the engine bay, including out of the catch can hoses or fittings (I sat there in a parking lot for about 10 minutes sniffing around my engine bay - probably looked a bit odd...)

    I did just replace a couple of PCV hoses, though (including the one from the valve cover to the intake area - see the one circled below - not sure what this does?), and I know the outlet fitting on my catch can is a bit small - I'll check whether there are any blockages in there when I drain the oil again tonight. I don't see how that would cause the smell to come out of the dipstick hole? My main concerns at this point are a) I haven't been able to get all the residual petrol out of the crankcase/sump or b) my new HPFP is also faulty... hoping things improve after my second oil change.

    Petrol in oil - next steps?-4uryutm-jpg

  9. #9
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    Update: after another oil change, the smell is definitely still there - at least as bad as before. Either I've bought a dud fuel pump or there's something else going on? I'm assuming a stuck injector would throw a code or affect performance (the car still runs beautifully and there are no new codes). I've ordered an OEM replacement hose to swap out for the crankcase-to-intake pipe circled above, since it's the only other thing I changed when I put the new fuel pump in, and I'll have a close look at all the catch can fittings at the same time. Any other ideas for bits I should be looking at? (I'm wondering about the charcoal canister, too?)

    The real mystery is how fuel might be getting into the oil, or whether it's just fuel vapours contaminating the oil and making it smell like fuel; it doesn't look like it's over-full, which I figure ought to suggest there isn't any more petrol getting into the crankcase. If a new hose and a couple of new catch can fittings doesn't sort it I'll probably throw in the towel and take it to my mechanic

  10. #10
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    I'd bin the catch can until you fix it. Fuel would evaporate quickly and be ingested by the engine.
    Have you looked at the fuel trims with vcds. Block 032, this highlights what's going on. It would remove lots of fuel at idle, as the breather fumes would be causing a 'rich' output from the lambda probe. Clearing the codes would zero the trims and they would adjust rapidly if there is still an issue. The engine needs to be at temp and it takes 3 minutes to commence from memory. I don't believe a bad injector would give the same symptoms. Especially As you have said that you recently fitted the hpfp upgrade.
    Fuel in the oil would also cause the engine to sound rattley when warm. Due to low viscosity.
    The car i saw with a bad hpfp seal also had massive over run pops even though it wasn't in the tune at all.
    Last edited by h100vw; 16-06-2019 at 11:01 AM.

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