Date:         Mon, 29 Oct 2007 21:23:17 -0700
Reply-To:     Michael Elliott <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Michael Elliott <camping.elliott@GMAIL.COM>
Subject:      Re: Why doesn't fuel shut off?
Comments: To: Dennis Haynes <d23haynes57@hotmail.com>
In-Reply-To:  <BAY125-DAV1768C9F8146232F54D8FF7A0920@phx.gbl>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

My foot off pedal full enrichment going down hill occurs at far slower
engine speeds than 5,800 rpm -- it occurs as low as 1,800 rpm.

--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR



On 10/29/2007 9:19 PM Dennis Haynes wrote:

> Actually Digi-jet does the fuel cut off at ~1,300 rpm. That is why they
> will sometimes get that idle surge. Too close. The only way the ECU knows
> if you are at close throttle or full throttle is AFM and engine speed. If
> you are running down a hill at 5,000 rpm, the combination will make the
> ECU think you are at full throttle and go to enrichment. This combined
> with high manifold vacuum will pull extra fuel through the injectors. They
> used to use throttle dash pots or the air cooled even used a decal valve
> to control throttle vacuum when the engine is excessively over run.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Michael Elliott
> Sent: Monday, October 29, 2007 7:06 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Why doesn't fuel shut off?
>
> According to Bentley's and the VW Digijet Protraining manual for the
> 1.9l engine, if the Throttle Idle Position Switch is closed (foot off
> gas) AND if the engine is at more than 1500 rpm, fuel to the engine will
> be cut off.
>
> I know the switch is working and that it is connected to the ECU because
> I have an LED which I can see while driving temporarily wired it. The
> LED goes dark when my size 10 is off the pedal, indicating that the
> switch is shorting ECU pin 4 to ground, and since that voltage comes
> from the ECU, the ECU "sees" the switch.
>
> I know the ECU is seeing engine rpms because it would just shut off fuel
> if it didn't think the engine was running.
>
> So it appears that the ECU is getting all the input it needs: throttle
> idle position switch and rpm.
>
> But when going downhill in gear, foot off gas as indicated by dark LED,
> and with the transmission revving the engine above 1500 rpm, the O2
> sensor goes full off-scale rich.
>
> The O2 sensor is new, and I'm monitoring it on my Ken Lewis-0-Matic O2
> meter. During normal driving and idling, it bounces around in quite a
> lively fashion.
>
> Based on this, it appears that the engine is NOT cutting off fuel as the
> manual says, and I am puzzled. I've tried a second ECU with the same
> result. What, oh what, could I be overlooking?
>
> --
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> KG6RCR
>