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EFI engines. When operating normally, does the regulator allow a consistent stream of fuel back to the tank or does it spit & spurt based on how much pressure its necessary to apply (hold back) in the rail?
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The outlet of the injector is exposed to manifold vacuum/pressure which varies depending on throttle movement, but the flow of fuel from the fuel pump is constant, the valve needs a reference to continuously change the amount of fuel bled to maintain constant fuel pressure to the injectors. The spring force in the regulator closes the valve when there is no vacuum in the intake manifold. When you start the engine the difference in the ambient air pressure and the vacuum pressure caused by the piston suction is present in the intake manifold and that vacuum pressure that is carried from it to the pressure regulator increases the pull on the regulator valve opening it up. The vacuum is greatest at engine idle and least at wide open throttle. So what the regulator is trying to do is to maintain a constant pressure difference between the inlet and outlet of the injector.
So to answer your question... Yes the volume of fuel return to the tank is constantly changing based on the constantly changing manifold vacuum.
This is just one of multiple reasons why it is so important that you detect and stop any vacuum leaks that you may have before you try to troubleshoot other problems. -
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