On Fri, Jul 27, 2012 at 2:34 PM, Scott Daniel - Turbovans
<scottdaniel@turbovans.com> wrote:

Hey Scott. Thanks for the reply.

> in a waterboxer Dififant or Digijet EFI system .
> the ECU fires all injectors at once.  Sometimes called 'batch fire'.

Huh. Well That's what I thought. Not sure what mechanic was thinking.
Maybe he and I were talking of 2 different things.

> so if it's cutting off one, it has to be cutting all of them off. it would
> be relatively impossible for just one to be shut off.
> The way the circuit works..
> power from the main relay is present at each injector.
> The ecu supplies ground to all of them at once....holding them all open for
> however many milliseconds the ECU determines is correct given the various
> inputs ....rpm, temperature, and whether throttle is at closed position, in
> between, or at WOT.

Right. This is what I had read and understood.

> I suppose an injector could be sticking open or leaking ..
> they are normally closed by spring pressure, and it takes grnd supplied by
> the ecu to open an injector, or all of them.

> I do like the idea of wondering if an injector is faulty , as in worn or
> leaking. That makes good sense.

Residual fuel pressure test showed system held pressure for at least
10 minutes. Almost 20 IIRC. Drop after that maybe 2 PSI ?

Even if an injector had a weak spring, I guess since the intake or
exhaust valve opens on downstroke, there wouldn't be enough vacuum
being pulled on a given cylinder to pull fuel through an injector with
a weak spring.

> I suppose the ecu could screw up and allow some injector open time during
> deceleration ...
> but it would do it to all of them as the ECU just sees the injector as one
> big four-part injector.

Good to know.

> My hunch is 'this path' about the ecu and decel operation being wonky
> .........is not it .

Ya it's a long shot I know. I just can't figure what is causing the surging.

I need to put more study into the relationship and wiring between the
idle stabilization module, ECU,  throttle switch etc. Something must
be hinky there.

Neil.

> On 7/27/2012 1:35 PM, neil n wrote:
>

>... Am still tracking
> down a surging issue. .....
> (Throttle switch test showed a nice square wave btw). He also kindly gave me a
> brief tutorial on the Vantage. FWIW, this Vantage (4.0) has a
> "Vanagon" section in it.
>
>...  he connected the Vantage
> to an injector wire, revved engine to 3K RPM, dropped the throttle.
> Meter graphed brief no voltage to that fuel injector wire, then
> voltage resumed. So that's good. ECU obviously stopped the FI pulse,
> then started it back up at idle. But that was one injector.
>
> In deceleration mode, is there one controller (my term) in ECU that
> turns off fuel to ALL injectors at the same time? Or, is there
> separate controller for each injector?
>
> On the 2.1, do all FI's pulse open at same time? (batch?) or in pairs?
> e.g.  1, 4     3, 2
>
> In other words, was this test of one injector sufficient?
>
> I have to wonder if there's a fault in the wiring or ECU that allows a
> fuel injector to pulse open in deceleration mode.

--
Neil n

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