Petrol in the air filter housing?

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Chief
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Petrol in the air filter housing?

Post by Chief »

Hi,
I decided to give my air filter housing a new lick of paint.

On dismantling the housing I discovered the air filter was seriously filthy, and quite black. There was also petrol (based on the smell) pooled in the housing.

I don't recall this ever happening before, so is this normal or an occasional thing that can happen?

I haven't driven the car much at all in a while, but the last time I admit I accidentally flooded the engine, could excess petrol have got into the housing that way?

Thanks,
Chief :)
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Re: Petrol in the air filter housing?

Post by Boomlander »

I don't think that neat petrol would find it's way into the filter housing unless the flooding was severe.
Is there a breather pipe from the rocker cover to the air filter?
This usually channels excess fumes from the engine via the air filter back to the cylinders.
When was the air filter last changed?

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Chief
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Re: Petrol in the air filter housing?

Post by Chief »

Yes the breather pipe was all connected.

In truth, due to family circumstances and then all the lockdowns the filter likely hasn't been changed in 7 years, and the car not driven much since - so yes it does need a replacing, though the fuel in the housing still came as a surprise.
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Re: Petrol in the air filter housing?

Post by ManyMinors »

I'm not sure how fuel can get into the air cleaner but the most common reason for a black air filter is probably a blowing exhaust manifold joint.
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Re: Petrol in the air filter housing?

Post by oliver90owner »

ManyMinors wrote: Tue Sep 28, 2021 11:30 am I'm not sure how fuel can get into the air cleaner but the most common reason for a black air filter is probably a blowing exhaust manifold joint.
Doubtful. I would expect the most common reason is the air cleaner gobbling up blow-by from gases passing the pistons into the crankcase, coating the filter with oily deposits. This could likely smell of petrol, particularly if the engine has been run on choke, with a far too-rich mixture, or with a misfire.

I would have expected petrol to have evaporated ‘in a while’.
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Chief
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Re: Petrol in the air filter housing?

Post by Chief »

oliver90owner wrote: Tue Sep 28, 2021 1:03 pm particularly if the engine has been run on choke, with a far too-rich mixture
Yes, this is how I flooded it. I used to live in a much colder area of the country where more choke was required to begin with and old habits die hard if you're forgetful through not driving much.
oliver90owner wrote: Tue Sep 28, 2021 1:03 pm or with a misfire
I did at one point get a loud bang, so whether that was a back fire or a misfire I couldn't say - it was certainly louder than the *pop* I associate with such things.
oliver90owner wrote: Tue Sep 28, 2021 1:03 pm I would have expected petrol to have evaporated ‘in a while’.
I've been surprised myself at how long petrol can hang around for ages without evaporating.

The last time the engine was started was likely last year, since it's been as easy to just push the car round as required and save on fuel.
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Re: Petrol in the air filter housing?

Post by pgp001 »

If your car has been stood a long time the fuel has probably "gone off".
It loses volatility after a relatively short time and does not evaporate as quickly as far as I am aware.

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Re: Petrol in the air filter housing?

Post by oliver90owner »

A misfire is generally considered as one, or more, cylinders not firing - either continuously or intermittently.

The last time our mini was started was around ten years ago. Tank was left about 1/3-1/2 full (according to the gauge). I expected it would need fresh fuel but we started it on that fuel.

Initially there was no fuel to the carb, but it fired and ran when fed with a ‘dash’ of easy start. Later the same day my step-son-in-law got it running by fitting an electric fuel pump in the line. It was subsequently running happily on the old fuel.

I expect the fuel pump was either dry or gummed up until the electric pump filled the lines/washed out any gum.

Where are you located to need ‘extra choke’? Not in the UK?
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Re: Petrol in the air filter housing?

Post by Chief »

oliver90owner wrote: Wed Sep 29, 2021 7:31 am Not in the UK?
I used to live in Western Scotland close to the sea. It used to be that you'd quite often need 3/4- full choke then after a few minutes you could reduce down to a small amount and then nothing.

Now I'm in the more temperate Midlands where I find you only need a small amount of choke (since the car hasn't been used much) and soon you can put it in and putter away.

Forgetfulness however had me on two occasions flood the car through having the choke fully out.

As to the fuel it's probably 50/50 old (2016~) and new~ish (this year) in the tank.

I'll likely get a full service kit etc. but I was curious about how the petrol got into the housing.
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