Re: CIS perceptions

["Frank J. Bauer" <frankbauer@thevine.net>]

At 03:35 PM 4/3/99 -0600, Dave wrote:
>>Yes, in CIS systems -- that's what the C stands for, continuous.
>
>Not quite correct.  The "C" does mean continuous, but it really means
>continuous pressure to the injectors.  As anybody who's done an injector
>test can tell you, the injectors used by the Bosch CIS only allow fuel
>to flow if there's a sufficient pressure difference from the fuel side
>to the manifold (engine) side.  In fact, that's one of the things you
>test for.  If they open with too low a pressure, you may have one
>cylinder running too rich compared to the others.  No fuel regulator
>changes can compensate for that.  If one requires too much pressure,
>you'll have a lean-running cylinder and woe unto you when you inspect
>that piston.
>
>In normal operation, a (relatively) steady pressure is applied to the
>fuel supply side of the injector.  As the piston drops during the intake
>stroke, the pressure on the manifold side drops.  Thanks to time delays,
>the pressure appears lowest to the injector physically closest to that
>cylinder.  At some point, the injector opens.

not quite correct.  as anyone who has read probst can tell you, the fuel
pressure is enough to overcome the spring pressure within the injector and
it subsequently continually injects fuel.  as anyone who has replaced
injectors or just the seats and seals can tell you, the injector is not in
the intake manifold, but rather in the head itself.
the CI in CIS stands for continuous injection, and that is exactly what it
does the entire time the engine is running...

frank