Date:         Thu, 6 Jun 2002 11:25:52 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Throttle switches
Comments: To: "joe@cedar.net" <joe@CEDAR.NET>
In-Reply-To:  <Pine.OSX.4.33.0206061005520.1362-100000@silver.cedarnetllc .com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 11:14 AM 6/6/2002, joe@cedar.net wrote:
>What do these switches actually do to the fuel system when
>activated?

The switches are in parallel (actually only one switch starting in '85
sometime).  They/it close at both closed throttle and WOT (Wide Open
Throttle); otherwise open.


>The throttle closed idle switch on mine is essentially out of
>the circuit. It appears that it is intended to be
>activated/closed when the throttle is closed,

correct.

>however at idle
>with this switch closed I get surging--back the adjuster screw
>out so the switch is no activated and it idles OK.

It would seem that your idle is set too high?  The action of this switch is
to shut off the fuel injectors whenever the rpm rises above 1500.  If you
were to coast down a long mountain with your foot off the gas, the engine
would be cold at the bottom...

The other end -- WOT -- causes the ECU to go into open-loop mode and enrich
the mixture for full-throttle operation.

>  This seems
>backwards to me as in order for the engine to idle the switch is
>noit activated, nor is it activated when accelerating.

Acceleration enrichment is actually taken care of by the over-swing of the
AFM vane.  Another small point -- this switch provides information, not
power control.  You gain the same amount of information by opening the
switch as by closing it, IOW the VW engineers chose the operation mode for
mechanical convenience and fail-safe -- no drastic problem if it fails
open, but hard to run the motor if it fails short, which is much less likely.

david


--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"