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Hi Folks,

had a little problem today. Cruising along the A3 approaching the M25 the 4A turned into a 2 cylinder. Pulled over and sure enough the rear two pots were not working.

Checked plugs, changed C/B module, changed coil. No joy.

Limped to a nearby petrol station and had a squint into the rear carb float chamber. Not a lot of fuel sitting there.

had a blow into the fuel pipe in the chamber cap and not a lot of blow going on.

The Grose jet ball had seized solid in to its brass housing. Apprx 5 years old.

 

Fitted a new replacement and all was well. But why did it seize. Most jets are held open by muck etc but never seized.

 

Roger

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Hi Roger

 

Just had a look on the search engine about Grose jets and there are many complaints about them on the British car forum.com!

Sorry can't cut and paste website as I'm not on my proper PC!

Edited by Damson6
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They did have bad patch for a while, cant remember how long ago but I thought it was longer ago than that and they had then fixed the the problem.Never used them personally so cant comment on their worth.

Stuart.

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Hi Roger

 

I bought a couple about 4 years ago and fitted them to the TR3B recently. They had the same problem you had with the balls kept getting stuck especially if they dried out. I have chucked them and returned to the SU ones. :unsure:

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Tinker ye not & stick to original type !

Sorry you had an interrupted journey back from the meeting, lucky you had a spare.

I use the SU type with the rubber cone end - never had any trouble.

 

Bob.

Edited by Lebro
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My guess is galvanic corrosion - ethanol makes fuel elctrically conducting. Stainless steel can then corrode the brass.

Although homebrewers don't see a big problem there's a useful hint for passivating brass in an oven here:

http://byo.com/stories/projects-and-equipment/item/1144-metallurgy-for-homebrewers

"To encourage a passive film on aluminum, copper and brass, wash the item thoroughly, dry it thoroughly, and then put it in your oven (dry) at 350 °F (177 °C) for about 10 minutes. This will help the anhydrous oxide layer to thicken."

 

Peter

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Galvanic corrosion could occur I suppose, if it did then I think the mechanism is more likely to be something like this:

1) ethanol sucks in water from humidity in air.

2) now we have water in ethanol petrol mix.

3)That will hydrolyse to acid.

4) Acid is now an electrolyte for dissimilar metals.

If that were going on though I would expect to see evidence of corrosion elsewhere and probably starting first, eg on the soldering of brass floats.

 

Your problem could be a combo of gunk corrosion cold welding, bit of flotsam getting in the way etc caused by just being left for a while and just a Sod's Law one off.

FWIW My experience of Grose jets is all positive, I had big problems with flooding and solved them with the Grose, no problems since. Of course its entirely possible that new SU jets, being new, would also have solved the problem. I think I read that there is a newer design of valve from SU which is claimed jam free. Probably I would order those now if I needed new valves, just now I don't.

 

MIke

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Hi Folks,

had a little problem today. Cruising along the A3 approaching the M25 the 4A turned into a 2 cylinder. Pulled over and sure enough the rear two pots were not working.

Checked plugs, changed C/B module, changed coil. No joy.

Limped to a nearby petrol station and had a squint into the rear carb float chamber. Not a lot of fuel sitting there.

had a blow into the fuel pipe in the chamber cap and not a lot of blow going on.

The Grose jet ball had seized solid in to its brass housing. Apprx 5 years old.

 

Fitted a new replacement and all was well. But why did it seize. Most jets are held open by muck etc but never seized.

 

Roger

 

Hi roger

 

Hope things are good with you apart from breaking down

 

I read this article yo might find it interesting seems that a minute piece of metall that can pass through the fuel filter

Can jam the ball open or shut ?

 

http://mgaguru.com/mgtech/carbs/cb112.htm

 

Hope this helps

 

Pink

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Thanks for your replies. I couldn't see any corrosion with the naked eye.

Sadly I dropped the valve which dislodged the balls so I never had chance to see if any muck was in there.

 

I'll keep it as a spare as it looks/feels like new.

 

Roger

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