[MV] Re: M151A2 problems

Stephen Somers (stephen.somers@virgin.net)
Tue, 15 Dec 1998 10:58:21 -0800

Further to my last, I have just been reminded of one other fault which we
discovered on the way and which was not the main cause but did make a
significant contribution to the overall effect of erratic running and
misfiring: The ceramic voltage dropping resistor which is (in our case)
bolted to the side of the engine compartment was found to have fractured.

This resistor is in series with the ignition coil primary winding but is
shunted by the start contacts of the ignition switch, to give maximum
spark during turnover. Once started, the coil energy is reduced to a more
sustainable level.

Because the resistor was fractured, once the engine was running the
supply to the coil would be interrupted at a rate of once per 'beat' of
the engine. The harder the engine was working, the more pronounced its
throb, the greater the interruption of the spark. This has the
dual effect of reducing the spark energy available and of delaying its
delivery to the plugs. It sounds just like a distributor problem.

Moral: It's worth checking the things you _know_ must be OK because they
are so rugged!

-- 
Steve Somers (Project Leader)

'75 Land Rover 101" Forward Control, 1-Tonne, General Service (62FL50 - Royal Artillery/2 Commando)

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