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MG MGB Technical - 78 MGB cuts out when it gets to temperature

My 78B runs great until it gets between the middle to top of the temperature range. It will also not restart until it cools down. I have checked the venting os the fuel tank and condition of the coil. I had a similar problem with a TD which was a coil breakdown. Engine is getting spark on the MGB.Could the fuel shutoff be causing the problem? I can however smell fuel. Any suggestions?

Thanks, Bill
G Ballard

Carry an extra spark plug, when it dies pull any plug wire, connect it to the spare plug, lay it on the block and see if you get a spark when cranking. If you have a nice blue spark, it may be fuel related, if not it is most likely the electronic ignition or the coil.
John H

If it cuts out when driving look at the tach while the forward momentum of the car is still spinning the engine. If the tach is not registering it is a problem in the coil LT circuit, which could well be the coil, they do have a known failure mode whereby they go open-circuit when hot. If the tach is still registering it is HT (which could still be coil) or fuel.

But if you say there is still a spark when it won't start, then it sounds like fuel, although you should check the timing of the spark on plugs 1 and 4 while cranking, and make sure the light is flashing on all four plug leads.

Checking fuel is a little difficult on a hot engine, but if you remove the air filters and blow gently in the float chamber vent pipes you should see fuel bubbling up out of the jets. If not, it sounds like the float chamber are empty, which could be the pump. If, when it cools down and does start, turning the ignition on is accompanied by lots of chattering from the fuel pump, then indeed the float chambers were empty.
Paul Hunt 2

This thread was discussed between 16/05/2007 and 17/05/2007

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