Date: Thu, 15 Nov 2007 21:01:25 -0800
Reply-To: Mark Drillock <mdrillock@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Drillock <mdrillock@COX.NET>
Subject: Re: Fuel pump relay cutout switch
In-Reply-To: <011101c82802$5c81df80$6501a8c0@TOSHIBALAP>
Content-Type: text/plain; charset=us-ascii; format=flowed
With my wiring suggestion, any time the driver wanted to check if the
kill switch worked all he would have to do is flip it off when parking
but while the engine was still running.
Also, don't you see that your suggestion uses a switched ground like
mine does and thus could fail the same way you worry mine could but even
worse? A short to chassis in the wire to the switch would allow the pump
relay to trigger on and run the pump whether the ECU wants it to or not,
defeating the theft security of the system as well as defeating the
role of the ECU in protecting the vehicle from major fuel leaks. An
accident that ruptured a fuel line while your method was employed could
be spectacular. Not likely to happen but my method avoids this
possibility since it does not interfere with the ECU control over the pump.
Since my suggested approach switches ground to a relay coil like yours
it likewise needs only a small wire and tiny switch but without the
small but real risk yours entails.
Mark
Scott Daniel - Shazam wrote:
> Yes, great layout - one small problem, were the wire to short to ground so
> it would always revert to 'will run safe mode' ...if the wire ever did
> short, the operator of the van would have a false sense of security since
> the switch he/she was turning off and on wouldn't really be doing anything.
>
> Personally, were I to want to employ this strategy as anti-theft
> ....disabling the fuel pump relay or fuel pump, I'd put a switch in the wire
> between the ecu and the fuel pump relay...the wire that supplies ground to
> the relay to energize it. Barely any current in that wire, so not a bad
> signal to go messin' with, and you could use a really tiny switch.
>
>
>
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Mark Drillock
> Sent: Thursday, November 15, 2007 3:25 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Fuel pump relay cutout switch
>
> The 3 wire options mentioned are all at the VW ECU wiring relay box
> which he may no longer have or which may have been modified. Of course
> he could do something under the van close to the pump like you point
> out. It all depends on how tricky you want it to be for someone to
> bypass the anti-theft system. Much easier to bypass one detectable
> outside under the van. Not so easy to bypass in the engine compartment.
> I would interrupt the fuel pump main ground wire with a relay contact
> added to the compartment in a visible location, controlled by a single
> wire run to a switch up by the driver. The single wire would in turn
> provide a switched ground for the relay coil.
>
> Running a single wire that provides only relay ground is safe since if
> it were to get rubbed through and short to the chassis the effect would
> only be to always allow the engine to run.
>
> Mark
>
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