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Date:         Mon, 23 Jul 2007 19:54:20 -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?
Comments: To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
In-Reply-To:  <002001c7cd88$275c5f80$0301a8c0@MASTERPC>
Content-Type: text/plain; charset="us-ascii"

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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