Date:         Mon, 27 Aug 2012 03:42:55 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Poor Hot Start Discovery - midway through solution
Comments: To: George Laubach <skiplaubach@COMCAST.NET>
In-Reply-To:  <500F6DD9-0782-4111-A7C0-72387FF6E269@comcast.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 05:16 PM 8/26/2012, George Laubach wrote:
>2. I'll check the charcoal filter valve. I've not ventured into that
>realm yet.

I'll pay you a dollar if that has anything to do with the case.

>3. I still have not read a crystal clear explanation of what the
>Temp II sensor does. I mean, what does the varying ohm signal from
>the Temp II sensor "cause and affect"?  For example, coolant hot,
>ohm signal low, this measure travels to the ECU via the connector,
>resulting in a signal pathway to what(s)?  And then what(s)? And for
>why(s)?  That sort of thing.  Please. Thanks.

The ECU is a computer that on the 2.1l engines handles fuel injection
and ignition including timing advance.  On the 1.9l it only does the
fuel injection; ignition drive is handled by a separate ignition
module and the distributor has conventional centrifugal and vacuum
advance/retard mechanisms.

In its fuel injection capacity it calculates the mass of air passing
through the engine and injects the correct amount of fuel to burn
with that amount of air, and it modifies that amount based on certain
conditions such as cold engine, wide-open throttle, decelerating with
closed throttle (modifies it down to nothing in that case), cold
idle, warm idle.  T-II is simply the thermometer that tells it about
engine temperature.  T-I is electrically identical (located inside
the AFM) and informs it about intake air temp, which it needs to
calculate air mass from measured air volume.  AFM is a spring loaded
vane-operated potentiometer that measures the volume of air passing
through.  All these operate by taking a five-volt signal supplied
through a resistor inside the ECU and grounding it through varying
amounts of resistance, causing it to vary.  The ECU reads the voltage
on each sensor line and interprets it appropriately, then uses it as
input for the calculations it's making about how long to hold the
injectors open.

Yrs,
d