QuestionHave car for two years, Fully rebuilt, Everything! Yesterday for the first time having driven 25 miles, stopped for ten mins. then the car refused to start. Plenty of fuel, plugs nice and clean(brown) Came back ten mins later and it started fine! Stopped for 10 mins on a call, and just got it started with a struggle. This never happened before. It is inclined to run on when switched off! Could this be fuel vapor? Have electronic ignition. Coil hot after 25 miles but cool today after 3 miles.
Am a member of the MG car club. Peter
AnswerHi Peter. This sounds like a classic case of fuel vapourisation.
Do you still have the original heat shield fitted between the carbs and the engine? On later cars they were made from a pressed material that eventually crumbles and falls apart. I see that someone is selling stainless steel replacements on eBay. They look good to me.
All MGBs (except low compression versions made for the USA) were designed to use high octane fuel, so if you are using 3-star then a change to BP Ultimate or Shell Optimax might help.
The running-on is not a good sign. It could be that your ignition timing needs adjustment or the tickover has been set too fast.
As an experiment, next time you stop to buy petrol, open the bonnet before you fill up. This will allow a lot of hot air to escape and might solve the problem. At least it will confirm my thoughts that it is vapourisation.
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ps - I gather that you also have a 1954 TF.
If you get the same problem on your TF please contact me,
because I make heat shields for the TF to solve this very problem.
