Engine Maintenance and Modification Bradley Artigue

FIAT 124 Spider
Engine Maintenance + Modification
9. Ignition
The ignition system in your FIAT is one of four types, all of which operate according to
similar principles. For the vast majority of Spiders, a distributor is mounted on the rear of
the cylinder head. Some early Spiders were fitted with distributors that run off of the oil
pump gearing. In both cases a shaft inside the distributor body spins in time with the
engine camshafts. The drive shaft turns a metal-tipped rotor that strikes connectors
inside of the distributor cap. When contact is made an electrical connection between
the spark plug and the distributor coil is made, sending a current from a high energy coil
and generating a spark that ignites the fuel mixture in the combustion chamber. As the
distributor rotates through its cycle the electrical pulse is sent to the tachometer,
resulting in a reading of engine speed in revolutions per minute (RPM).
The 1967-1972 Spider had a simple “single point” distributor, where a single set of
points was activated by the movement of the distributor shaft. From 1973 (on the
1592cc engine) through 1978 FIAT used a “dual point” distributor, where one set of
points was used for starting and another for running. The first set (the starting set)
created additional advance during starting. After 1978 an electronic system was used.
The points used in prior models were replaced with devices that electronically controlled
the spark and vacuum controlled the advance. A fourth system was made available by
FIAT for a brief period of time, and is coveted by many Spider owners. The Marelliplex is
a mechanically-advanced electronic distributor. To a Spider owner it eliminated the
dependence on the throttle-controlled vacuum pulse of the stock electronic unit, yet
used all stock components otherwise. All four systems are extremely reliable when
properly maintained.
9.1 Ignition Components
For our purposes, the major components of the ignition system are the coil, distributor,
spark plugs, and wires. Depending on the type of system (electronic or mechanical)
there are other pieces and parts, such as points, condensers, magnetic pickups, and
control modules. We’ll cover the important pieces that you need to understand in
getting to know your Spider.
The Coil stores electrical energy. It is a cylinder bolted to the firewall and is easy to spot
as it has one big wire coming from the top and smaller wires from either side. On
Spiders made from 1979 to the end of production the coil was part of a pack that
included a finned housing and control module.
The Distributor is an electrical switch, using engine rotation to propel a rotor against a
series of contacts. As the distributor shaft turns an electrode on the rotor makes the
connection between the coil and each of the spark plug wires. A set of points (1967-
1978) or a magnetic pickup (1979-1985) releases energy from the coil into the wires.
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