Ethanol fuel residue?

[RichardMc]

I'm looking for views on here regarding residue inside the carb bowl. Not specifically Jupiter related except that the carbs we are running are the Dellorto 32 FRD that are used on the Jup. We have a pair of these on a Javelin that was running rough, very rough. Everything was tried to solve the problem, new ignition, dizzy, coil, plugs, timing (you get the idea). The car has an inline fuel filter before the punp and a filter king after the pump and there is no residue or anything showing in the fuel. As a final throw of the dice we removed the carbs, not an easy task on the Javelin with the FRD fitted. Many skinned knuckles later we had then on the bench, when opened up the float bowls were full of aluminium / grey coloured mud. Lots of this stuff, once the fuel evaporates away it turns to a grey chalky powder like polyfiller. It's amazing the car ran at all.
Now the big question, where did it come from? Has anyone else seen this? It can't be from dissolving the aluminium of the carb bowl because it was everywhere and there was so much of it, if that much aluminium has dissolved we would have had a big hole but the bowls looked Ok when cleaned.
Could it be dissolving something in the tank, it was cleaned and seal coated many years ago, but it doesn't show up in the filters. If this mud was suspended in the fuel why would it drop out of suspension in the carb and not the filter king glass bowl?
Would love to hear the collective wisdom on this, pictures enclosed.

https://ibb.co/4NhjVQ6
https://ibb.co/GJGZJrG
https://ibb.co/7GnRcr2

[Keith Clements]

You need to look into the history of those carbs, that residue may have been there since 1990.

I have seen various types of residue on carb bowls, some like sand, some like treacle, some like your grey stuff.

Clean out and try again.

[RichardMc]

We cleaned it all out, could be build-up over the years. Geoff has the same carbs on the Jupiter so I'll have a look inside these too. Much easier to do on the Jup.

[AmilcarJohn]

Hmmm good tip. I'm also experiencing rough running/poor tickover on the Jupiter fitted with these carbs. I'll check too.

[AmilcarJohn]

Finally had chance to check my Dellortos: clean as a whistle. Turns out my car's poor running was caused by the Filter King, as I had changed the diaphragm and it messed up the pressure setting.

Could your fine debris be from a slosh tank sealant? I've had that problem on a previous car.

John