HS6 piddling petrol

[PaulAA]

Chaps

I have twin HS6s on an ex-US TR6, which have performed faultlessly for two years.

This morning, they did not. Although the engine started and ran smoothly enough, a strong smell of petrol revealed that fuel was evidently being pushed down the overflow into the carbon cannister and flooding quite lavishly onto the garage floor.

To help me target the cause, would this be symptomatic of a broken float, a contaminated jet or something else that hasn't crossed my mind?

Advice much appreciated.

Paul

[JohnD]

Both carbs flooding would point to excessive fuel pressure.

Just one - take off the float chamber and inspect.   Dirt in the valve?  Yes, float not floating, perforated, but that would be unusual, IMHO.

I'm not familiar with the Carbon canister system, so cannot say more.

John

[Nick Jones]

Probably just one carb and probably a lump of crude in the needle valve. A sharp smack on the side of the float chamber is sometimes enough to resolve it.

A slightly less probable concern is that ethanol has eaten your float and its sunk.

Do you have an inline filter?

Nick

[PaulAA]

Thank you, both.

Yes, I have an in-line fuel filter, but common wisdom has it that petrol in Poland has a higher ethanol content than in the West.

Being a lowly carb car, it has a mechanical fuel pump, but the quantity of the stuff piddling off the front valance was impressive. Not.

I will do some float chamber thumping when I return to the ranch tomorrow and report.

John, the carbon cannister is merely a capture device at the end of the overflow pipework, so no more than an obstruction to identifying the source of the streaming fuel.

Cheers

Paul

[Nick Jones]

54 minutes ago, PaulAA said:

John, the carbon cannister is merely a capture device at the end of the overflow pipework, so no more than an obstruction to identifying the source of the streaming fuel.

Exactly this....... a US feature for reducing "fugitive emissions" from the float chambers.

Nick

[PaulAA]

Looks like it's resolved - when I took off the lids, the rear carb float chamber was noticeably fuller (and overflowing when I loosened the cover).  Nothing to see (and nothing fell out when I manipulated the float / needle).  All parts appeared to be moving freely.

I wonder whether the c. half litre of fuel that went through the carbon cannister was enough to do a proper flushing job on the active particles inside it...

Thanks again.

Paul

[PaulAA]

Dang... not cured.  Repeated today, quite some distance from home.  But the cause was a shard of black rubber, probably a piece of fuel pipe barely more than eyelash size, lodged in the needle valve opening.  A lesson in cleanliness and diligence - it was undoubtedly something I left behind when I was replacing the supply and overflow pipework...

Still, stripping down the bowls provided a good half hour's entertainment for the diners on the terrace of the restaurant we were (involuntarily) parked outside.  Slightly disappointed that we didn't get a round of applause when the job was done, though.

Paul

[Nick Jones]

Ah, quite a common cause. The pipe stubs can be quite sharp and really good at shaving slivers off the inside of hoses as you slide them on. Sometimes the slivers stick inside the needle valves with the results you've experienced. Sometimes they get further and partially and intermittently block the jet tubes.

Can relate to the restaurant story. Once spent a good hour fettling Dad's elderly Peugeot in the car park of a posh hotel somewhere in the Blyde River canyon area of South Africa. The manager was most unimpressed. Probably even less impressed by the state of his car park after we left hue to a certain amount of err, haemorrhaging.........

Glad you were able to sort it and get home!

Nick

[PaulAA]

Good call, Nick.  Probably time to do a more general carb knock down and clean up...

My own haemorrhaging experience was when I replaced the oil pressure gauge pipe and omitted to use the leather washer.  I only became aware of how lavishly it had widdled oil over the communal garage floor on my second 'test drive' circuit.  An object lesson in how far c.500cm3 of warm oil will disperse over an epoxy-finished concrete floor.

Neighbourly wrath unequivocally incurred.

Paul