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MG MGB Technical - Temporary loss of power..

I have a 1968 B fitted with two SU-caburetters.

Just recently the following problem began to occur: sometimes (while driving) the engine suddenly looses power for a second or three, the gas pedal feels numb, and the needle on the tachometer starts to bounce up and down. Then, all of a sudden, everything is back to normal again. A few times the engine have completely gone out(leaving it a bit hard to start again) but usually i runs OK again after a few seconds. I have experienced this phenomena both at high and low speed. I have subsequently checked the fuel pump(new), the batteries, and the caburetters which have been adjusted recently. Normally, I use fuel with an octane rating 98, but have occasionally used ´95 with a lead-additive, which my mechanic says should be ok.......can anyone shed some light on this problem.

Thanks for a nice site
Lars Andersen, Copenhagen-Denmark
LA Lars

Check the ignition, things like coil, points, condenser, low and high tension leads.
Cecil Kimber

The most likely culprits would be your ignition switch or ignition relay, if so equipt.
George B.

Check the brown lead wire down at the starter soleniod.

It's held on by a push-on tab connector and it sometimes
gets loose. When this happens, the engine sputters,
the tach bounces, etc.

Disconnect the battery, squeeze the tab connector
gently with pliers and push it back on. Re-connect
the battery - and go.
Daniel Wong

Tach bouncing indicates an ignition LT problem i.e. white feed to coil, coil, points, condenser and connections between them as per Kimber. But if the ignition warning light flickers on as well (assuming it works in the first place) the problem is probably in the ignition switch, the brown to it or the white from it as per George. If other circuits e.g. the lights flicker as well then check the conenctions at the solenoid as per Daniel.
Paul Hunt

Thank you very much. /Lars
Lars Andersen

When a similar problem occurred on my 71 bgt, it turned out to be a bad fuel filter. I assume you checked this already?
Sam C

I haven´t been able to locate the fuel filter yet(!) - does the ´68B have a fuel filter?

Thanks again, Lars
Lars Andersen

I had same symptons on my V8 Factory GT, traced fault to a bad coil
HTH,
Nigel
n.griffiths

Problem solved! - I changed the coil today and now everything runs smoothly. Went for a long ride this aftenoon.....

Lars
Lars Andersen

This thread was discussed between 04/07/2002 and 06/07/2002

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