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MG MGB Technical - Won't restart for 5 mins

Hi, Has anyone experienced this. 1972 MGB which runs and drives well, tickover a little lumpy but if it stalls it refuses to restart, not a hint of firing, until you have waited 5 mins then it is running sweetly again. I suspect fuel evaporation or mixture or fuel pump, but although the exhaust smells a bit rich, pulling the choke seems to help a restart.

Where to start? Carbs were stripped and rebuilt 1000 miles ago. Pump replaced at same time.

Thanks, Andrew
Andrew Walton

What colour are the plugs when it refuses to restart? Are they wet with fuel?
Chris at Octarine Services

You say it's running sweetly, but tick over is "lumpy". The lumpy idle could just be carbs out of balance on the idle stops. If it's a hot start problem, 5 mins would not be long enough for things to cool down. Presumably you are "on" HS4's. The next time it happens, switch off and take the top off there float chambers and look at the fuel levels. You will be able to tell if they are starved or flooding.
It could also be a coil problem, when it stalls, note the rev counter and feel the coil, or, if on points, a failing condenser. If it is an ignition problem the rev counter will fall to nil as the car is stalling, if it's fuel it will continue to hop around until the engine has stalled.
Allan Reeling

Thks for ideas. Will check out and reply. Chris, plugs are dry but fuel filter has fuel. Cheers Andrew
Andrew Walton

Sounds like you need to go through a full set-up of valve clearances, points gap/dwell and timing, and carb air and mixture balance. Maybe replacing service items unless they are known to be recent. However that can be a double-edged sword as replacement components particularly for the ignition can fail very quickly due to poor quality.

It's never going to be evaporation at this time of year, especially in the UK.

You say stalls, do you mean it cuts out when driving or you stall it with not enough revs when pulling away, for example? If it cuts out when driving then as said you must look at the tach before doing anything else and see if that has dropped to zero or is still registering. If it's dropped to zero it is an ignition LT problem i.e. ignition supply, coil, points, distributor, or any of the interconnections. Also look at the ignition warning light, and assuming that works normally if that is glowing it is loss of ignition supply from the ignition switch. If the tach is still registering normally it is HT or fuel, or possibly condenser.
Paul Hunt

This thread was discussed between 06/02/2014 and 08/02/2014

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