Date: Sat, 28 Jul 2012 01:43:29 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Fuel Injector (or wiring) Question: Deceleration,
Fuel Shutoff Mode
In-Reply-To: <CAB2Rwfj3quJ1x99=kPH02nAn7Hwbsv5GiaXaXpdkREiTSP2EAA@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"
Unless your battery-starter cranks very slow or you compression gauge is off
120 is not good compression for a water boxer. Time for a leak down test and
measure valve lift. Bad valves/guides can cause all sorts of funky stuff.
Except for the O2 sensor system being difficult to diagnose the rest of the
FI system usually works or it doesn't. It is often blamed for something else
being wrong.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
neil n
Sent: Saturday, July 28, 2012 12:54 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Fuel Injector (or wiring) Question: Deceleration, Fuel Shutoff
Mode
the issues are a surge decelerating from 2500 and surge accelerating from
lower rpm.
compression ranges from 120 - 140 so that's good. engine power is good.
i get what you mean about even a few things ( or one ) causing the engine to
run poorly.
at this point I'm grasping at straws. I've run almost all the Bentley
digifant checks and have replaced the muffler o2 cat temp sensor all tune up
parts except hall ( wires to it are fine) At this point all i can see as an
issue is the ECU and or a wiring issue.
Frustrating! :)
On 7/27/12, Scott Daniel - Turbovans <scottdaniel@turbovans.com> wrote:
> 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
>>
>> '88 Slate Blue Westy to be named.
>>
>> '81 VanaJetta 2.0 "Jaco" http://tubaneil.googlepages.com/
>>
>> Vanagon VAG Gas I4/VR Swap Google Group:
>>
>> http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas
>> -engines
>>
>
>
--
Neil n
65 kb image Myford Ready For Assembly http://tinyurl.com/64sx4rp
'88 Slate Blue Westy to be named.
'81 VanaJetta 2.0 "Jaco" http://tubaneil.googlepages.com/
Vanagon VAG Gas I4/VR Swap Google Group:
http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engine
s
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