Date: Fri, 26 Sep 2008 14:27:14 -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: Question about testing O2 sensor with digital meter
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response
there is no Cold Start injector on a waterboxer vanagon of course.
I sure say 'ditto !' on Mark and everyone's suggestion to ........
check fuel pressures,
and ...........check the basics !
When you get lost........back up and start over.
That notion about 'getting it in your mind that something is OK or a certain
way' ...........as Mark says.......that can be a real trap.
When you're just kinda lost................Always go back and start from
square one..........
just like someone brought you this van and you have *no idea* what they may
have done to it ..........etc.....- naturally you'd likely start by removing
and inspecting the spark plugs, and checking compression just to start
diagnosing.
And .........while I rarely find fuel pressure incorrect............if you
have a fuel pressure gauge it's real easy to check. I often just leave the
fuel pressure gauge connected while I troubleshoot things, test run it
between trying this or that etc. So convenient they have that test port
right there on the engine. They sure got that right !
I'm sure grounds have been mentioned, but you always need to keep those in
mind.
And for sure.........the only real resistance checks that you can really
count on must be measured at the ecu plug.
I would always look at the plugs too, that's your best visual indication of
what's going on in the cylinders.
Always remember to consider clogged or restricted cat or muffler.
Doesn't happen too often..........but it's something that always needs to be
considered.
And the IR temp gun on each exhaust pipe .........that can really find a
weirdly functioning cylinder in a few seconds even.
"it's just a blockage or leakage of fluids or electrons."
just keep after it until you get it !
----- Original Message -----
From: "Mike S" <mikes@FLATSURFACE.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, September 26, 2008 2:03 PM
Subject: Re: Question about testing O2 sensor with digital meter
> At 01:40 PM 9/26/2008, Jim Felder wrote...
>>David, as I just wrote to Larry A., it climbs to around .843 and stays
>>there as it runs rougher and rougher.
>
> If the closed loop adjustment is working, the voltage should move back
> and forth across ~0.45V. They are extremely sensitive, a tiny bit lean
> and it will be well below 0.45V, a tiny bit rich and it will be quite a
> bit higher. If it sits at one reading without moving much, then the
> fuel control probably isn't working right.
>
> If your's is steady at ~0.8 volts, AND the engine is running rich, it's
> not the sensor, it's something else. If the sensor were bad and putting
> out that voltage, the ECU would be make the fuel mixture leaner (and
> it's probably trying to do so now).
>
> Have you checked the fuel pressure? If the regulator is bad and the
> pressure too high, that might cause an uncorrectable rich condition.
>
> You might also try unplugging the cold start valve (aka "fifth
> injector"). If that's always on for some reason, it would make the
> engine run rich. It could also be leaking, in which case unplugging it
> wouldn't change anything.
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