FIAT 124 Spider
Engine Maintenance + Modification
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The air flow meter also activates the fuel pump. Unlike the 3-5psi pumps of carbureted
engines, fuel injection pumps must produce the high pressure that forces fuel into a mist
while passing through the injector bodies. The pump fitted to the FIAT 2000 engine
produces between 50 and 80psi, which is controlled to between 36 and 43psi by the fuel
pressure regulator. As air passes through the air flow meter a chrome rod closes a
circuit that activates the fuel pump. So long as air is passing through the meter the
pump will run; once the vehicle stops drawing air the pump will shut off.
5.3 Cold Starting Components
Let’s discuss the fuel injection components that are used during cold-starting of an
engine. When a cold engine is started it requires substantially more fuel than a warm
engine. This is due to condensation of the fuel in the air/fuel mixture. A device called a
thermo-time switch (see Figure 34) is located directly under the Spider intake manifold.
This switch determines the length of time the cold start valve, remains on. The cold
start valve is a fifth injector, inserted into the side of the plenum. This injector sprays
fuel directly into the air entering the plenum. This rich mixture remains until the engine
reaches a temperature sufficient to eliminate condensation of fuel and keep the engine
running. This process takes from 2 to 8 seconds depending on the coolant temperature.
Figure 34: Cold Start Operation in the Bosch L-Jetronic System
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