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MG MGB Technical - Engine cuts out at high speeds

Hi Guys and Girls,

I have a 1977 MGB. It has been running very well for the last couple of years. Recently it has begun cutting out after driving for a while (maybe 15 minutes). At low RPM this doesn't seem to be a problem. I had the carb re-built about a year ago, I have replaced the fuel pump about two years ago, I have recently replaced the Electronic module for the distibutor, the cap and the rotor. I have also replaced the fuel filter. I am not sure what else to look at. I had one fellow suggest that maybe the diaphram in the carb was bad (ripped or perforated) I have checked it and it seems to be just fine. I have ordered and new carbon canister for it. Any Suggestions?

Thanks Dean

Dean Banta

Dean: You didn't mention if you had replaced the ignition coil or not. If you are still running the 6V coil that was standard with the Opus Ignition that your MGB came with and have replaced the Opus with a pertronix or Crane ignition, then you need to get a 12V coil to match the rest of the ignition. Also, in my years of repairing MGs, I've come across a number of folks running ATF in their Strombergs which does cause the diaphragm to go bad. Personally, I would only use the Stromberg for target practice with a large hammer - The SU HIF44 or HIF6 replacements are much better for a single carb MGB.
John Perkins

Dean - See my Fuel Delivery Troubleshooting Guide at:
I would be suspicious of a clogged fuel tank vent (only because I have had it happen on our MGB). Cheers - Dave
David DuBois

Thanks for the suggestions guys. I will check the coil. I have not replaced it and I am not sure what vintage it might be. It does kinda act like a clogged fuel tank vent. I will check that as well.

Dean Banta

This thread was discussed on 09/07/2007

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