| While working at European Sports cars, I
would like to share a problem I would often come across with engine misfires on MGs. Of
course, I had the luxury of a Sun 2000 engine scope, to show me where the bad spark
pattern was occurring. On a few occasions, I found that the tachometer, as it was wired
into the ignition, was causing a disruption in the spark pattern and causing an engine
misfire.. Just pull the black and
white wire off the back of the tachometer to see if there is any improvement in the
spark pattern The black and white wire are routed into the ignition
system.
Of course on the very old MGs you will not have this problem as the tachometers are cable driven, and have nothing
to do with the ignition system.
One major component that can cause a bad spark pattern is
the old-style points distributor. Many things inside the distributor can cause an engine
misfire, a worn points plate, bad condenser, or worn or pitted points. I had very little
success fitting "rebuilt" distributors, as most of the rebuilding consisted of
sandblasting the distributor body. The 100% cure to repair an old distributor I found was
to convert it to electronic ignition. This is very simple to do and is smog legal. I put
an Allison electronic ignition on my MG in 1982, I fitted it, set it in 1982, and have not
touched it since.
Paul Lewis
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