[Mgs] Intermittent miss

[Henri Lefebvre]

Peter,

My Triumph TR8 was acting in a similar fashion: it would quit
momentarily, or totally, but it started very easily then ran well.

It turned out to be the loose ignition switch unit. The wire harness
plug on the back side of the key switch was loose and following some
slight movement/rattle of the key chain in the switch the power would
turn off. In my case I re-tightened to harness plug to the switch and
all is good.

Henri
1971 MGB GT
1975 TR6
1980 TR8

On Mon, Jul 30, 2012 at 4:49 PM, Peter Schauss <rpschauss at gmail.com> wrote:
> My 1980 MGB has developed and intermittent miss.  This morning it started
> and ran fine until I had gone about 5 miles on the parkway.  When it began
> to cut out, the tachometer needle took a nose dive toward zero.  At one
> point it cut out so badly that the engine stopped completely and I had to
> pull off of the road.  It started immediately, however.
>
> Given the behavior of the tach I believe that the problem is on the primary
> side of the ignition possibly the following components:
> - the connections at the fuse block.
> - the ignition relay
> - the primary side of the
> - the electronic ignition amplifier (I have the CEI system with the
> amplifier mounted on the fender.)
>
> I have tentatively eliminated the fuse block connections and the relay
> because the gas and fuel gauges both continued to work when the engine
> started to miss and they are on a circuit which is fed by the ignition
> relay.
>
> That leaves the coil and the amplifier both of which are original.  So my
> questions:
>
> - When the coil fails when it gets hot is it the primary or secondary
> winding which fails?
> - Would a failing electronic ignition amplifier cause symptoms like this?
>
> Keep in mind that this car has a ballast resistor in series with the coil
> for normal running and that when the starter is energized the coil gets the
> full 12 volts.
>
> If the problem is in the amplifier I have three options:
> - replace it with a stock amplifier
> - get the Petronix insert for my distributor
> - replace the distributor with a Petronix
>
> Which do you suggest?
>
> Thanks,
> Peter Schauss
> 1980 MGB
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