Something Died

[mwb0205]

Hiya

I was driving my 200k mile, but pretty well-maintained, mk2 8v hard-ish, when the power started to ease off. So, I eased off, felt the power stop easing off, gave it some more power, then almost straight after heard what sounded like a couple of bolts bounce down the underside and lost all power. Pulled over and had a fire in the engine bay, but put that out fairly quickly.

I haven't tried to swap the battery and see what happens - it's totally dead at the moment

Where do I start looking for the cause / answer!?

/I've got a mk3, so I can take me time with the mk2 (and would quite like to learn a bit about the car and engine by working on it)

[mk2_abf]

where was the fire coming from in the engine

[mwb0205]

the fire was behind the engine. i don't know if just slamming the lid down put it out and / or it burned itself out

[mk2_abf]

seems like a leaky fuel line could of caught a light off you exaust maifold

[Khare]

seems like a leaky fuel line could of caught a light off you exaust maifold

Impossible. Petrol needs a spark or a naked flame to ignite. If you drop petrol on a red hot manifold it will just evaporate off.

Could possibly be oil, or an electrical fire.

[AudiA8Quattro]

Even so it would only take the smallest of sparks from any of the surrounding electrical circuits to start a fire.
Anyway petrol is supposed to ignite at 246 degrees C.

[danny_p]

no spark needed,   the 10/40 engine oil that got sprayed over my exhaust when arod liberated itself was more than happy to ignite

[AudiA8Quattro]

All oils and fuels will have a flash point, when they will spontaneously combust.
Petrol is 246 degrees C.
How hot is an exhaust manifold?

[Khare]

no spark needed,   the 10/40 engine oil that got sprayed over my exhaust when arod liberated itself was more than happy to ignite

in that case the internet is WRONG! i read somewhere that it needs a naked flame or spark to ignite. Mind you that is petrol, as you said your oil lit up, but thats oil, its different to petrol...

[JC]

no spark needed,   the 10/40 engine oil that got sprayed over my exhaust when arod liberated itself was more than happy to ignite

in that case the internet is WRONG! i read somewhere that it needs a naked flame or spark to ignite. Mind you that is petrol, as you said your oil lit up, but thats oil, its different to petrol...

so this post was pointless then, yes 

and yes fuel CAN ignite off a VERY hot exhaust, no naked flame or spark required - just heat - i know these things from my bike days 

The Fire Triangle
The Fire Triangle is a simple way of understanding the factors of fire. Each side of the triangle represents one of the three ingredients needed to have a fire – oxygen, heat, and fuel – demonstrating the interdependence of these ingredients in creating and sustaining fire. When there is not enough heat generated to sustain the process, when the fuel is exhausted, removed, or isolated, or when oxygen supply is limited, then a side of the triangle is broken and the fire will die.

 

Heat

A heat source is responsible for the initial ignition of fire, and heat is also needed to maintain the fire and permit it to spread. Heat allows fire to spread by removing the moisture from nearby fuel, warming surrounding air, and preheating the fuel in its path, enabling it to travel with greater ease.

Fuel

Fuel is any kind of combustible material, and is characterized by its moisture content (how wet the fuel is), size and shape, quantity, and the arrangement in which it is spread over the landscape. The moisture content determines how easily that fuel will burn.

Oxygen

Air contains about 21% oxygen, and most fires require at least 16% oxygen content to burn. Oxygen supports the chemical processes that occur during a wildland fire. When fuel burns, it reacts with oxygen from the surrounding air releasing heat and generating combustion products (i.e. gases, smoke,embers). This process is known as oxidation.