Date: Fri, 31 Oct 2014 17:02:46 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Single wire Oxygen sensor: Substitution report..
In-Reply-To: <02aa01cff534$06cff430$146fdc90$@gmail.com>
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The sensor does need a return path and it is done through the exhaust and
engine. There has to be a complete circuit. The ECU sensor input can also be
tested with a battery. Ground the input and the engine should go rich,
connect the battery positive terminal to the lead and ground the negative
and the engine should go lean.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Stuart MacMillan
Sent: Friday, October 31, 2014 1:57 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Single wire Oxygen sensor: Substitution report..
The 02 sensor does not need to be grounded, but the ECU reading it does. The
millivolt current is generated chemically between two internal electrodes,
only one of which is connected to the ECU (the electrode the electrons have
left for the other one, creating a + voltage), and the ECU measures that
voltage to its internal ground. Note that the heater has two wires, ground
and hot, it's the only part of the sensor that does need grounding, and it's
not done through the exhaust for the reasons you mentioned. The heater wires
are shielded to prevent inducing a current in the signal wire.
I've installed single wire sensors on my MGBs for voltmeter carburetor
tuning, and here is a good method for bench testing an 02 sensor that has
saved me money over the years (from
http://www.gnttype.org/techarea/ecmsensors/O2sensors.html):
"Testing O2 sensors on the workbench:
Use a high impedance DC voltmeter. Clamp the sensor in a vice, or use a
plier or vice-grip to hold it. Clamp your negative voltmeter lead to the
case, and the positive to the output wire. Use a propane torch set to high
and the inner blue flame tip to heat the fluted or perforated area of the
sensor. You should see a DC voltage of at least 0.6 within 20 seconds. If
not, most likely cause is open circuit internally or lead fouling. If OK so
far, remove from flame. You should see a drop to under 0.1 volt within 4
seconds. If not it's likely silicone fouled. If still OK, heat for two full
minutes and watch for drops in voltage. Sometimes, the internal connections
will open up under heat. This is the same a loose wire and is a failure. If
the sensor is OK at this point, and will switch from high to low quickly as
you move the flame, the sensor is good. Bear in mind that good or bad is
relative, with port fuel injection needing faster information than
carbureted systems.
ANY O2 sensor that will generate 0.9 volts or more when heated, show 0.1
volts or less within one second of flame removal, AND pass the two minute
heat test is good regardless of age. When replacing a sensor, don't miss the
opportunity to use the test above on the replacement. This will calibrate
your evaluation skills and save you money in the future. There is almost
always *no* benefit in replacing an oxygen sensor that will pass this test."
Stuart
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
OlRivrRat
Sent: Friday, October 31, 2014 10:05 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Single wire Oxygen sensor: Substitution report..
Don
How did you end up dealing with the Ground ~ It should, I believe,
be taken
care of through the Body of the O2Snsr being in contact with the
ExhaustSystem ~
But I choose not to trust that as the Joints&Bolts in that Path tend to get
Crudded
over time, so I ScrewClamp a wire to the O2SnsrBody & attach the other end
to a
Good BodyGroundPoint ~
ORR ~ DeanB
On 30 Oct , 2014, at 10:34 AM, Don Hanson wrote:
> I run digifant engine management for my inline VW ABA Jetta motored
> vanagon...same as the stock Vanagons but with the inline motor
> providing the go..A few weeks ago I had some problems with my engine
management
> system and traced it to a dysfunctional Oxygen sensor. I'm almost
> positive the problems were a result of bad wiring between the O2
> sensor and the ECU, but I have no actual confirmation of that.
>
> Anyhow, I was unhappy with the cost of replacing the Bosch 3-wire
> heated Oxygen sensor in my rig...the best I could find was about $70
> for another Bosch heated sensor, and that one didn't even have the
> proper plug for my wiring harness...So I did some research, called
> around a bit and asked...and the general response was that I could
> replace that 3 wire heated oxygen sensor with the single wire Bosch
> sensor and save myself about $50 without any real downside to engine
performance. But......No one
> would actually come right out and tell me that. Lotta "Oh, that should
be
> OKs"...and "I don't see any reason why that wouldn't work
> fine"s....There was also some nebulous opinion as to how to properly
> connect the sensor...Should the shielded wire loom carry a grounding
> connection or not...etc...
>
> Anyhow I bought a single wire Bosch from Van Cafe and installed it.
> The results are quite satisfactory. The only downside has been that
after
> sustained highway driving if you shut off the motor for a short while
> the idle speed is a little low...low enough to stall sometimes...for
> just a couple of seconds, until the O2 sensor gathers enough heat to
> resume proper function, I guess.
>
> I have regained my fuel economy...back up to 24.xx mpg after 3000
> miles with the new sensor. the O2 sensor i again modulating the fuel
> mix properly....When running with the O2 sensor disconnected from the
> ECU, I was seeing around 4-6mpg less gas mileage but the motor felt
> quite happy and strong..
>
> So, in my case, I successfully saved some money on that part and gained
> back my good gas mileage. Here's a handy app to help you track your
> fuel...there's one for the smart phones, too....
> http://www.fuelly.com/dashboard