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MG Midget and Sprite Technical - Fuelling query

Hi All,
1972 midget Mk 3 1275 engine.
I have recently made a conscious change to using Tesco Premium 0 or < 5% ethanol fuel, from the usual Tesco > 5% ethanol fuel but my car seems to be running rich ( from looking at the plugs and the exhaust )
I checked the carbs and they do all the right sounds when I lift the pins but it still " feels" rich and the blue exhaust which I couldn't previously
Could the " better" fuel cause this ?
Any ideas of how to sort this?
cheers all
colin
colin frowen

Colin,
yes the ethanol does burn differently but driving style and distance and the heat will also influence plugs and exhaust but not enough for blue smoke (unless on heavy choke).

Lots of short journeys of say less than 15-20 miles in one go at sunny Sunday afternoon pace to the local village show can clog things up especially if choke is in prolonged use and/or mixture is rich or a bit rich. You could try driving in a more spirited way for longer on longer journeys as they could blow the plugs cleaner.

You could adjust the mixture during cooler weather without the engine getting too warm too.

Blue smoke could be oil burning so stick you finger in the exhaust to check.

Also if your valve clearance aren't right or have changed then this can have effect, check and if required set up tappets, points/plugs, timing and mixture in that order, mixture last.

Also check your air filters are truly clean before any adjustments.

That's me out of ideas.

Nigel Atkins

I get what feels like a rich running condition when the ambient temperature is high. The alcohol in the fuel has a low boiling point and this seems to be the cause. I have heard it boiling in the tank when the car is parked over hot pavement.

Low or no alcohol fuel is best for extreme heat driving conditions.
Glenn Mallory

At the risk of being Mr Obvious is it possible that your "choke" cable is smidge tight? I ask because that's exactly what happened to my car a while ago.
Nigel made some worthwhile points, especially that slightly retarded ignition timing might contribute. Modern fuels seem especially sensitive to this.
Greybeard

This thread was discussed between 28/07/2022 and 07/08/2022

MG Midget and Sprite Technical index

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