Quote:
Originally Posted by Senna-F1
Since my 41 psi was with vacuum line connected and engine running, would the gauge have registered more had I unplugged it? Wondering what effect it has with line connected vs not connected.
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Yes. Your engine operates at a vacuum normally.
There is a piece inside the fuel pressure regulator that moves with changes in intake manifold pressure.
When you set it initially, it has to be a atmospheric pressure to give a good baseline for fuel pressure.
When idling (engine operating at vacuum), the regulator will send less fuel (pressure) to the engine since it does not need as much fuel to idle as compared to driving.
When you really get on it, that piece moves to allow less flow back (more resistance to flow), increasing fuel pressure proportional to intake manifold pressure, ensuring that the engine is getting the correct amount of fuel as pressure increases.