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Old 24-01-2020, 01:07 AM   #1
ShepWoofWoof
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Default Fuel in Oil! How do I check for damage?

Hi all

Running a 1978 bay with a 2L CU engine in it.

Was on a trip up to West Coast of Scotland and noticed it running bad, drop in power and horrendous fuel consumption. Finally worked out that it had fuel in the oil (oil stick level far too high and smells or petrol.) Got it recovered back home, but more than likely did several hundred miles with petrol in the oil.

My question is, what damage am I likely to have done, and how can I check for that?

Have searched but most posts seem to simply state dire warnings if you run like this, without stating what. Any help appreciated.
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Old 24-01-2020, 01:42 AM   #2
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Worst case scenario is washed cylinders walls and possibly crank / cam journal and bearing damage. Did you get the oil pressure warning light on at all?

Either way, drop the oil because you're going to be changing it anyway. Have a look at the oil and see if there's any evidence of metal particles in the oil (i'm assuming you're not running an external filter). You'll need to find the culprit for the fuel getting in the oil in the first place which is likely due to a leaking fuel pump diaphragm. If the oil you dropped looks ok (look for a shimmery or glittery like look to the oil) and after fixing the culprit for the fuel getting into the oil in the first place, fill it with fresh oil and fire it up. Check for the oil pressure warning light operation to be normal after startup and then monitor how it behaves on a run etc and whether or not the pressure light comes on at all - outside of what would have been normal for the motor previously. You MAY have got lucky and get away with no damage.

Last edited by callookoval; 24-01-2020 at 02:09 AM..
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Old 24-01-2020, 08:21 AM   #3
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As above

But would recommend you find the issue as it is likely to happen again.

What fuel pump are you running ? I had issues with a electrical fuel pump with too high pressure pushing fuel through the carbs into the engine

Michael from wayoutwestie really explains it well and is a really helpful guy


https://www.wayoutwestie.com/aircooled-tech/


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Old 24-01-2020, 10:01 AM   #4
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Do you have ICT carbs? The float valves wear too quickly on these carbs, 9/10 buses with fuel in the oil seem to have them fitted which is a pity as they're simple effective carbs otherwise.

You have an oil filter which is a good thing as it should have caught any "bits", but you may not see much evidence in the oil itself so if the oil is clean, cut the filter open and examine that too.

Loss of power and the miles you suspect drove with fuel in the oil are bad signs obviously but if it starts after you have replaced the oil and stopped fuel getting in you'll have to judge for yourself from oil pressure and the noise(s) it makes compared to how it was. Or...

Strip it right down and rebuild it before any possible damage gets worse because the more worn an engine is, the quicker it wears. E.G. big ends - a bit of slop allows the conrods to literally hammer on the bearings.

Last edited by Zed999; 24-01-2020 at 10:38 AM..
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Old 24-01-2020, 10:39 AM   #5
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Also, if you have ICTs you can get fuel syphoning. This happened to me, fuel was trickling through the carbs and ending up in the sump. I replaced the needle valves and fitted a solenoid shut off valve in the fuel line, so fuel can only flow when the ignition is on. Really cheap to buy and easy to fit.

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Old 24-01-2020, 10:16 PM   #6
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Quote:
Originally Posted by callookoval View Post
Worst case scenario is washed cylinders walls and possibly crank / cam journal and bearing damage. Did you get the oil pressure warning light on at all?
Nope, no oil pressure warning light, which I presume is good?
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Old 24-01-2020, 10:19 PM   #7
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Quote:
Originally Posted by starsky2727 View Post
What fuel pump are you running ? I had issues with a electrical fuel pump with too high pressure pushing fuel through the carbs into the engine.
Stock fuel pump, which I presume is manual. Someone mentioned that it was most likely a fault here, and specifically with the gasket/seal so I'm thinking of replacing that anyhow.
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Old 24-01-2020, 10:25 PM   #8
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Quote:
Originally Posted by Zed999 View Post
Do you have ICT carbs? The float valves wear too quickly on these carbs, 9/10 buses with fuel in the oil seem to have them fitted which is a pity as they're simple effective carbs otherwise.

You have an oil filter which is a good thing as it should have caught any "bits", but you may not see much evidence in the oil itself so if the oil is clean, cut the filter open and examine that too.

Loss of power and the miles you suspect drove with fuel in the oil are bad signs obviously but if it starts after you have replaced the oil and stopped fuel getting in you'll have to judge for yourself from oil pressure and the noise(s) it makes compared to how it was. Or...

Strip it right down and rebuild it before any possible damage gets worse because the more worn an engine is, the quicker it wears. E.G. big ends - a bit of slop allows the conrods to literally hammer on the bearings.
It has what I presume are the original 32/36 and 34/36 PICT dual carburetors.

Thanks for the tip on the oil filter, good shout.

I'm tempted to take out and strip anyhow, as last time I did that I didn't have the money to do it properly/invest it better kit. However, not clear if we're just talking heads or actually a full engine strip.
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Old 25-01-2020, 01:23 AM   #9
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Quote:
Originally Posted by ShepWoofWoof View Post
Nope, no oil pressure warning light, which I presume is good?
It's certainly not a bad thing. In the 2276 I ran before the motor I have now now, i got about a litre of fuel in the oil due to an issue with carbs floats in 48 IDA's. I had no choice but to drive about 50 miles with the fuel in the oil - which I did, at low revs and trying not to put the motor under load. Later, I changed the oil out, new external filter, fresh oil etc and fired it up, it was fine. When torn down a few months later for a refresh, everything was perfect internally. Little bit different in this case as the fuel basically went straight into the cylinder bores whereas in your case it's gone straight into the case but - the point I'm making is, you CAN get lucky and no damage be done in either case. Or you could be unlucky and your motor is ruined. By fitting

It was me that mentioned the fuel pump diaphragm. In stock pumps, they are known to fail and when they do, it just dumps raw fuel straight into the case. That would be my first port of call for the culprit. By fitting a new fuel pump, fresh oil etc and trying it, you're not going to worsen the situation if the motor is already damaged - if you know what I mean.

And the guy talking about a strip, he is talking about a full strip - bottom end, the lot. Which obviously is the best advice but not always reasonably practicable .

Last edited by callookoval; 25-01-2020 at 09:48 AM..
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Old 25-01-2020, 11:08 AM   #10
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Type-1 fuel pump sat on top leaks into the case, but does type-4 which is on the bottom corner? I have to admit I don't know but maybe not.
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