Date: Mon, 23 Jul 2007 20:52:06 -0700
Reply-To: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Subject: Re: Is ECU involved in getting power to fuel pump when turning
ignition switch on?
In-Reply-To: <12f2979f0707232024y6f2833cbu33caee137bd56901@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"
Hi. Thanks for mentioning a specific page this time.
You're offering that as a trouble shooting chart for the guy's no-start
condition, I take it.
That page paints with a pretty broad brush stroke, I must say.
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Billy Hirt
Sent: Monday, July 23, 2007 8:24 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Is ECU involved in getting power to fuel pump when turning
ignition switch on?
I believe the answer(s) are on page 4
http://www.loam.org/vw/Vanagon/VanagonProTraining/DigiFant/
Billy
On 7/23/07, Scott Daniel - Shazam <scottdaniel@turbovans.com> wrote:
>
> A few corrections.....
> Any one is free to comment of course.
>
> The fuel pump comes on three ways ....one is the 'pre-run' .....when you
> go
> to start any vanagon with this system, you 'should' or could/should turn
> the
> key to 'on' and listen for it to run a few seconds and shut off.
> If it doesn't' do that, I'd say it is 'a failure' technically. That by
> itself won't keep the engine from starting or running if the pump is able
> to
> run during the second way it's made to run....
> Which is during starter cranking. Interesting Dennis that you've
> identified
> that the 'cranking signal that energizes the fuel pump relay does so even
> if
> it's in say, Drive, and the starter won't then of course be
> cranking......not sure if I ever noticed that. Interesting.
>
> The third way the fuel pump keeps running is after the engine is fired up,
> something tells the ecu that the engine is actually running ( as opposed
> to
> just the ignition is on ) .....this is for crash safety. If the engine
> stalls, but the key left is on, you want the fuel pump to be
> stopped. That
> it gets that from the ignition....i believe you. Thanks for that.
>
> This is the part that seems strange to me ;
> "Note that power
> for the pump is also the feed for the injectors."
>
> What are you saying ? . The power for the fuel pump, which comes from the
> fuel pump relay...is also the power that's on one side of the injectors ?
> Or
> the power source for the Main relay ?
>
> The injectors get their power from the Main Relay, right next to the fuel
> pump relay in the small black box above the ignition coil , I believe.
> I'm
> not looking at diagrams, just sharing from how I understand the system.
> The ECU fires the injectors by supplying ground to all of them
> simultaneously......like one big injector in 4 parts.
> The fuel pump relay and the main relay are kinda not related.
> When you turn on the key, ....i believe that's when the main relay gets
> energized.......and power is available then to the ecu, to the injectors,
> and for oxygen sensor heat on 2.1's.
>
> Additionally, when you turn on the ignition, that's when the ecu does it's
> 10 second thing to pre-pressure the fuel system by running the fuel pump.
> (
> you can do this 10 times in a row on an new or empty fuel rail, btw, to
> get
> fuel where it belongs. )
>
> When you turn to 'start' ....the fuel pump is run again, this time by the
> start signal from the key, the injectors are already powered up, ready to
> let fuel under pressure be released by being held open so many
> milliseconds
> by the ecu, the distributor is turning and making ignition and sending it
> to
> the right places, all conditions to run are met, and it fires up ! Once
> running the fuel pump is kept running by the ecu supplying ground to the
> fuel pump relay, which it does because it knows the engine is running,
> since
> it gets that info from the ignition system, as you pointed out .
>
> But in no way can I agree that ""Note that power for the pump is also the
> feed for the injectors." ...........is an accurate statement, unless you
> actually meant something a little different.
>
> Correct me if that is not the case.
> Scott
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Dennis Haynes
> Sent: Monday, July 23, 2007 5:18 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Is ECU involved in getting power to fuel pump when turning
> ignition switch on?
>
> Take another look. Pin 3 on the ECU operates the fuel pump relay by
> completing the chassis ground. Pin #1 takes a signal from the start
> circuit and the ECU should also operate the fuel pump while the engine is
> cranking. On automatics, this signal is before the neutral safety switch
> so the fuel pump while run when the key is turned to start even if the
> selector in not in neutral or park. Yes, the pump will run without the
> engine actually cranking over.
>
> The pump not turning on when the ignition is switched on is not always a
> failure. It is an ignition pulse that operates it for the short time. The
> pump must run while cranking though. After start, it is the ignition
> pulses that keep the pump on to keep the engine running. Note that power
> for the pump is also the feed for the injectors. A bad hall sensor or coil
> can keep the pump from running along with no spark.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Benny boy
> Sent: Monday, July 23, 2007 7:26 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Is ECU involved in getting power to fuel pump when turning
> ignition switch on?
>
> No
>
> http://www.loam.org/vw/Vanagon/VanagonProTraining/DigiFant/
> (page 42-43)
>
> I hope the ignition switch was check/replace!
>
> Ben
>
>
>
> On Mon, 23 Jul 2007 14:45:52 -0700, most david <dmost@YAHOO.COM> wrote:
>
> >It's been one month, and I've made no real progress in solving my
> "intermittent power at fuel pump when turning key on" problem in my '87.
>
> At least one person has suggested the ECU (I've ruled out fuel pump relay
> and ignition switch).
>
> For those of you who are good at reading the circuit diagrams in the
> Bentley, can anyone tell me with certainty if the ECU is involved in
> getting
> power to the fuel pump when the key is turned to the on (not start)
> position?
>
> Since I can't use the vanagon now due to not being able to count on it
> starting, I appreciate any help that anyone can offer.
>
> Thanks,
> David
>
>
>
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