Engine Maintenance and Modification Bradley Artigue

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FIAT 124 Spider Engine Maintenance + Modification barrel type mounted to the inside of the driver’s side fender on the early models and the passenger side on the late models. The electronic ignition system of the 1979-1985 Spiders can be identified by the large coil pack mounted on the passenger side fender wall. If stock it will have an enclosure of aluminum fins to each side and a control module on the bottom back. Most electronic distributors will be stock, with a vacuum canister mounted on the side. Two wires wrapped in a small diameter tube run from the distributor pickup to the coil pack. The now rare FIAT replacement part known as the Marelliplex system looks identical except that it has no vacuum canister on the side of the distributor (and no way to install one; a sure way to identify a fake Marelliplex is to see if the base has the opening and fitting for the vacuum dashpot). Table 9: Ignition System Components Series Seal Cap Rotor Condenser Breaker Points or Pickup Unit Coil Unit AS 9915908 9925467 9924654 9913848 9913862 BS1 9921512 9925467 9924394 9922454 7111161 CS1 9921512 9925467 9924394 9926424 (74-77) 7111161 9929180 (73) CS2 9921512 46340 56290 859818 9937730 4386220 CS0 9921512 46340 56290 859818 9937730 4386220 DS0 9921512 46340 56290 859818 9937730 4386220 9.3 Ignition Advance In your Spider the basic ignition timing is set to either 5 degrees (1438cc), 0 degrees (1592cc, 1608cc 1756cc) or 10 degrees (1978 1756cc and all 2000cc) behind top dead center (BTDC). This means that the spark plugs “fire” when the crankshaft angle is almost at the absolute top of travel. This is called ignition advance. Advance is a term applied to timing an engine in such a way that the spark is delivered just before the piston reaches top dead center. This is necessary because there is a time lag between 68
FIAT 124 Spider Engine Maintenance + Modification when the spark is delivered and the fuel/air mixture and cylinder pressures are optimal. If the spark occurs at top dead center then the piston is already moving down when these optimal conditions are possible. Therefore the spark is forced to occur just prior to top dead center; the fuel/air ignition begins and reaches its maximum at the appropriate time. A variation in ignition advance is required to maintain optimal efficiency. Beyond the “hard” setting of 0 or 10 degrees BTDC the ignition distributor has a metal plate that moves according to engine speed. This movement, governed by either centrifugal or a combination of centrifugal and pneumatic force, varies the advance so that the spark is delivered at the optimal point, up to 32 degrees BTDC (depending on series, some were limited to 28 degrees). Spiders manufactured prior to 1978 have centrifugal advance plates, the movement of which is driven by the spinning of the distributor shaft. As the shaft increases in speed the centrifugal force moves the advance plates outward, increasing the advance. On Spiders manufactured after 1978 (the CS2, CS0, and all Pininfarina Spiders) the vehicles were fitted with a Marelli electronic ignition with a pneumatically-operated advance mechanism. It has often been misidentified as a pollution control – it certainly is not. The diaphragm in the distributor varies the amount of advance when it is pulled by the drop in air pressure that occurs when the throttle opens. As the throttle opens and more air enters the engine the amount of advance increases. This design makes the ignition advance dependent on the actual load of the engine rather than the speed of the engine; arguably a more efficient design. 9.4 Firing Order and Initial Timing All FIAT Spiders fire in the order 1-3-4-2. The initial timing is set so that the camshafts and crankshaft are in the initial position, with camshafts aligned with pointer holes and crankshaft aligned to the block mounted pointer. When this initial position is met the engine is set to fire on the #4 cylinder (figure 43). Crankshaft Camshaft Distributor Rotor Position PULLEY TIMING MARK IS AT 0° BTDC Figure 42: Initial Ignition Setting 69
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