1978 MGB leaks gas from 1 of the 2 SU carbs, runs rough and will not hold idle. car has not be started for 1 month.

Asked by Nov 08, 2015 at 02:04 PM about the 1978 MG MGB Roadster

Question type: Maintenance & Repair

SU leaks gas, is the float on one of the SU cards stuck

6 Answers

9,770

You probably have the float level set too high or the carb float has a hole in it

69,285

Get a set of Grose jets to replace the old style needle and seat. Replace the floats while you are at it. http://www.northwestimportparts.com/MGB-Carburetor-Parts- i58.aspx

69,285

Moss Motors -- http://www.mossmotors.com/Shop/SearchResults.aspx? SearchText=grose&WebCatalogID=0

69,285

Leaving an older car sitting for a month without starting it will cause problems with the carbs getting gummed up. Run a good fuel system cleaner like Seafoam and drive the car more often. My car with 3 SU's does not like sitting but a drive of a few miles will usually clear up a rough idle. I installed Grose jets 20 years ago and have never had a problem with fuel overflow! If your car sits a lot be sure and use Sta-bil in your gas as well. Good luck!

5,245

The leak is probably the small cork gasket on the lower jet housing. If it has not been driven in awhile, they dry out and can leak. Before you spend a lot of money, remove the lower jet and check the gasket.

9,770

Those carbs should be easy to get apart ... my guess is if it sat for a while the float may be stuck or the needle is not closing the feed

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