vacumn
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Re: vacumn (david90)
When the engine's sucking air in thru the intake manifold, that makes a partial vacuum in the manifold. Especially if you don't have the throttle wide-open.
You don't want air leaking into the manifold everywhere, only the air coming in through the throttle. The ECU 'knows' about that air, so it injects the right amout of fuel...
You don't want air leaking into the manifold everywhere, only the air coming in through the throttle. The ECU 'knows' about that air, so it injects the right amout of fuel...
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From: Cincinnati,, Oh
Re: (david90)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by david90 »</TD></TR><TR><TD CLASS="quote">right on. How does emission controls work off of vacuum?</TD></TR></TABLE>
The MAP sensor monitors vacuum. The ECU makes adjustments based on the reading of the MAP sensor.
The MAP sensor monitors vacuum. The ECU makes adjustments based on the reading of the MAP sensor.
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From: san francisco, ca, usa
Re: (david90)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by david90 »</TD></TR><TR><TD CLASS="quote">right on. How does emission controls work off of vacuum?</TD></TR></TABLE>
your fuel pressure regulator works off of manifold vacuum... the evap system checks for leaks by monitoring pressure and vacuum within the evap system... some egr valve uses ported vacuum and some uses a vacuum in the exhaust stream...
your fuel pressure regulator works off of manifold vacuum... the evap system checks for leaks by monitoring pressure and vacuum within the evap system... some egr valve uses ported vacuum and some uses a vacuum in the exhaust stream...
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Joined: Feb 2001
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From: san francisco, ca, usa
Re: (david90)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by david90 »</TD></TR><TR><TD CLASS="quote">what are the methods of tracking down leaks?</TD></TR></TABLE>
there are usually 3 solenoids in the evap system. the ecu will open and close these in certain configurations. i.e., the purge solenoid will be open and the vent and anti drain-back (or something like that... the one that prevents vapor from reentering the gas tank...) will be closed. when the fuel vapor is purged from the system, it creates a small vacuum in the system. the purge solenoid will close and the system will/should hold the vacuum. there is a pressure differential sensor within the system that'll detect whether the vacuum is remaining steady.
unfortunately, if there is a leak, a code will be set, but it will not tell where the leak is.
there are usually 3 solenoids in the evap system. the ecu will open and close these in certain configurations. i.e., the purge solenoid will be open and the vent and anti drain-back (or something like that... the one that prevents vapor from reentering the gas tank...) will be closed. when the fuel vapor is purged from the system, it creates a small vacuum in the system. the purge solenoid will close and the system will/should hold the vacuum. there is a pressure differential sensor within the system that'll detect whether the vacuum is remaining steady.
unfortunately, if there is a leak, a code will be set, but it will not tell where the leak is.
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