While trying to track down the cause of a rough idle/vibration recently, I was checking the vaccuum lines and connections. I noticed that when I pilled the vaccuum line between the resonator and the fuel press. reg. there was no change in the engine's idle. I then discovered that there was no, zero, zilch suction on this line whatsoever. Is this correct?
Coach Steve
There will not be a vacuum from the resonator. That will be at atmospheric pressure, minus any slight drop from the air filter which should be zero drop if the filter is reasonably clean. That connection from the fuel pressure regulator to the resonator supplies filtered air to the regulator.
It would be positive in relation to the manifold vacuum. The resonator is at atmospheric pressure.
It also supplies filtered air for the engine PCV system to breathe in through the other larger hose connected to it.
It also supplies filtered air for the engine PCV system to breathe in through the other larger hose connected to it.
The only way there would be vacuum at that port on the resonator would be if the filter is clogged, or you have your hand over the air inlet and you are choking off the air! Manifold vacuum may run 18-22 in-hg at idle, but there won't be any significant vacuum on the atmosphere-side of the throttle plate. Just whatever drop across the filter element there is, which should be close to none. I doubt you could measure the pressure drop across a filter with a typical vacuum gauge.
The PCV system draws air through the engine from the filtered air source in the resonator, and through a PCV tube into the intake manifold to be burned.
The PCV system draws air through the engine from the filtered air source in the resonator, and through a PCV tube into the intake manifold to be burned.
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