47silver wrote:
Quote:
Some CIS cars have a switch located on the air sensor. This switch starts the fuel pump when the sensor is raised. Since My 75 fuel pump starts when the key is on the pressure is always high. If yours has the switch on the air sensor then
jumper the fuel pump to on and then test the valve again. If you have spray then your cold start valve is ok.
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On the cars equipped with the safety switch ('76 and later CIS cars), the fuel pump, as well as the cold start valve, operates during the entire time the starter is operated and so provides fuel pressure to the CSV. This operation is provided by the fuel pump relay. The CSV doesn't need to rely on residual fuel pressure to operate during startup.
I have never seen any evidence that any fuel is provided by the injectors during startup, as a certain amount of airflow is necessary to raise the airflow sensor. I'll be the first to admit that I don't know if the engine, just powered by the starter, provides enough airflow to raise the sensor plate. However, the first few "power spins" of the engine doubtless provide enough airflow, and fuel to the injectors, to keep the engine going after the starter is released.