Quote:
Originally Posted by MartinClan
I had thought about a vapour lock. But I recently put a pressure gauge in the hp fuel line which indicates all is well on that side.
Robin
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I don't properly understand the 'Vapour Lock' phenomenon but unless the vapour lock is in the pump, I would expect the test pressure to be OK, but for some reason the injection mechanism (or carburettor) seems unable to function properly to feed vaporised fuel into the induction side of the engine.
I need to read up/research this because it seems pretty fundamental. I am in correspondence with somebody who seems to have some experience of temperature control in IC engines.
I know my carbs are being supplied with cool (liquid) petrol but the engine refuses to fire, when a few seconds before, it was running well. I know this isn't exactly your problem but it's similar, it seems to me that as soon as the engine stops and induction ceases, the carb venturi heats up, or to put it another way, ceases to be cooled by the passage of air in depression, which cools the air
and the carb venturi. The latent heat in the carb body then immediately warms the venturi and the vaporises the fuel in the jet, apparently preventing the venturi from sucking liquid fuel from the jets.
Allowing the engine mass to cool below a critical temperature, allows the engine to start, because the liquid fuel is no longer vapour, the main jets which are not designed to pass vapour therefore the mixture isn't rich enough to start the engine.
That's the rough bones of my theory but it needs some meat, in the form of accurate temperature monitoring at the critical points. Some research as to what temperature ethanol bearing fuel vaporises, also what effect atmospheric depression has on all this, the boiling point of liquids varies with atmospheric pressure, therefore the depression in the venturi may affect the boiling point therefore the formation of vapour which seems to stop the show. Wish I was a chemist! LOL
Hope some of that makes sense.