Date: Thu, 7 Aug 2014 06:37:05 -0700
Reply-To: Don Hanson <dhanson928@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Don Hanson <dhanson928@GMAIL.COM>
Subject: Re: Digifant II O2 sensor....My questions answered...
In-Reply-To: <1407386426.27413.YahooMailNeo@web164601.mail.gq1.yahoo.com>
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I don't know exactly what O2 sensor WAS in the system, but the wires and
the plug, those were from the Digifant Cabriolet, 92 model year, I think.
The wiring from the O2 sensor, that had your gray wire and that wire was
connected directly to the head of the motor. The other side of the plug,
from the harness back to the ecu, that had a blank space where that gray
wire would have gone. So I think...I think ...the black wire (Ground?)
simply ended at that long flat four prong plug...and the old O2 sensor was
grounded at the engine, not the ecu.
That is what caused me a bit of confusion...Which I ultimately solved
with cave-man diagnostics..."drive it and see what happens"
Both of the techs I spoke to were right..
.The fellow at Van Cafe said..."We sell lots of these single wire Bosch O2
sensors to Vanagon owners...just disregard all the wires except the signal
wire, they are inconsequential now"
Randy at Techtonics Tuning told me "I can't be 100% sure, advising on the
wiring, because there were a few different versions of that particular
vehicle shown in my books." Digifant II is Rest of the world and Digifant
I is California Only, by the way. Randy told me that Digifant is more
dependent on the signal from the o2 sensor for mixture control than the
Motornic. This seems to match what I saw when running without the O2
sensor connected..I lost almost 8 miles per gallon when running in the full
rich default mode without an O2 sensor..That implies that once it was
re-installed correctly it really helps the fueling..
I can not detect any difference between the way it runs now with how it
ran with that 4 wire O2 sensor...other than perhaps I am getting very
slightly better gas mileage now...We shall see after a few more tankfulls.
On Wed, Aug 6, 2014 at 9:40 PM, Robert Keezer <warmerwagen@yahoo.com> wrote:
> Were you using the 4-wire O2 sensor that came with the ABA?
> The Motronic Mk3 O2 sensor is different from the Digifant O2 in that it
> has an extra wire(gray).
> The Motronic O2 sensor grounds internally through the gray wire. The
> internal ground for the O2 is connected to the ECU, not the vehicle frame
> ground.
> Unlike the Digifant O2, The Motronic O2 is not externally grounded.
>
> The Motronic 4-wire O2 will not function with the gray wire ungrounded.
>
> When I upgraded my 82 Westfalia with the ABA and Digifant 2, I didn't
> understand the purpose of the 4th gray wire, so I left it disconnected.
> I failed the emissions test. I scanned the fault code memory of the ECU
> and "no O2 sensor" was displayed.
> After studying the Mk3 Bentley, I saw the diagram showing the gray O2 wire
> connected to the ECU.
> Robert
> 1982 Westfalia
>
> ------------------------------
> *From:* Don Hanson <dhanson928@GMAIL.COM>
> *To:* vanagon@GERRY.VANAGON.COM
> *Sent:* Wednesday, August 6, 2014 8:58 PM
> *Subject:* Digifant II O2 sensor....My questions answered...
>
> The vehicle and motor..84 Vanagon with Inline VW...a 92 cabriolet 1.8 liter
> head and everything else mounted on a 93 2.0 liter ABA block. I kept the
> digifant engine management and used the 1.8 liter head because it fits into
> the vanagon using VW diesel engine mounting system and no bumps or raised
> rear deck..A lot of the parts are directly from a vanagon digifant
> system...
>
> So my O2 sensor failed...perhaps because the wiring is/was aged and
> brittle and maybe shorting out....I had another spare one. the same 4 wires
> but not the VW plug. "We" deduced that the plug I had been running matched
> the 92 Cabriolet wiring diagrams...so anyhow I wired in the other 4 wire O2
> sensor and that worked fine for a few days, then IT failed also, or the
> wires shorted out again, or perhaps the wires shorted out and caused the
> second O2 sensor to fail also...I don't know for sure, but that seems
> likely.
>
> I looked for that particular O2 sensor with the proper plug, briefly,
> but after seeing them priced way up there ($75+) and considering the state
> of the wiring from my engine harness out to the existing plug...I decided
> to simplify with a less expensive single wire Bosch.(<$30) I got one
> from our Van Cafe California Vanagon supplier, who's tech told me it would
> work just fine...and so it did/does. I had a question on whether to
> attach the old ground wire from my computer to something...nobody really
> seemed to know, for sure..so I capped it off, along with the two wires to
> the heating element, which the single wire Bosch does without, also.
>
> So I eliminated that sketchy plug and 3 rotten wires and simply spliced
> to the signal wire, after cutting back that shielding a little to get to
> wires in decent condition. The van ran just fine without any O2 sensor
> connected, but very rich and my fuel mileage dropped to just 18mpg.. In
> order to know if the O2 sensor I installed, rather than trying to test pin
> outs or millivolts with a meter, I figured I'd just run a tank of fuel
> through and see how far I got, thereby knowing if the sensor was working,
> and if there was any decline in function using a single wire one rather
> than the expensive heated one that cost about 4 times more. Happy to
> report that I am back to my previous long time confirmed fuel consumption
> with this tank giving me 25mpg driving some city but mostly rural..
>
> I do not have a cat convertor in my system and the O2 sensor is right
> near the exhaust manifold, so it heats up quickly, I guess, judging by no
> decline in fuel economy...
>
> Thanks to all who tried to help me with this...electronics in the engine
> are not my forte... and I have to say any time I can eliminate 3 wires
> and two plugs without any downside...I am all for that.
>
>
>
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