Date: Fri, 27 Jul 2012 21:04:07 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Fuel Injector (or wiring) Question: Deceleration,
Fuel Shutoff Mode
In-Reply-To: <CAB2Rwfi2egNqEg+guigVA_LFRbg6PRPxxk7TQ2_T_ODb_BeW+w@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
hi neil,
there are waterboxer vans running around without their electronically
controlled valve even working or connected..
not that I recommend that.
my point is ..carefully investigate everything you can ...
and I don't see the control unit or valve causing uneven deceleration..
Be nice to read what the exact symptom is again.
I can not emphacize enough about air and vacuum ..those all have to be
pretty right,
including exhaust.
One van 2.1 van I fixed ..
I found 3 things bascially wrong ..
idle switch, timing too advanced, and an exhaust leak very close to the
oxygen sensor.
The guy didn't think those 3 things would fix his van ..
I think it did though. He said he'd let me know if it acted up again.
mechanically ..everything has to be pretty right about intake air, air
leaks, vaccum, exhasut , compression etc. ..
though low compression is usually a consistent vague weakness..
like a waterboxer engine can run perfectly with say only 80 psi in one
cylinder..
and it's good to know what that is too- compression or leak down.
'after' everything that is mechanical and 'air' related ...upstream or
downstream of the cylinders ..
then you think about the elctronics ..AFM, Temp sensor, throttle switch
etc.
and make sure fuel delivery is good.
When I do start checking injectors , I can go through a dozen to find 4
pretty nice ones.
On 7/27/2012 3:57 PM, neil n wrote:
> 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
>
> 65 kb image Myford Ready For Assembly http://tinyurl.com/64sx4rp
>
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>
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>
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>
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