Date: Mon, 23 Jul 2007 22:19:31 -0700
Reply-To: David Kao <dtkao0205@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Kao <dtkao0205@YAHOO.COM>
Subject: Re: Is ECU involved in getting power to fuel pump when turning
ignition switch on?
In-Reply-To: <010e01c7cdaf$26977720$6401a8c0@TOSHIBALAP>
Content-Type: text/plain; charset=iso-8859-1
--- Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM> wrote:
> See SDF below -
Yes, I agree. It's just a magnet and a coil inside. It seldom gives
problems. But the external connection wire could go bad. That's somehat
a little more likely than the Hall unit inside the distributor. But still
very likely comparing to other things.
David
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> David Kao
> Sent: Monday, July 23, 2007 9:42 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Is ECU involved in getting power to fuel pump when turning
> ignition switch on?
>
> If you look at the fuel pump relay circuit you may wonder why the fuel
> pump relay gets power from the #15 terminal of the ignition coil.
> This terminal does not have +12V there. The #1 and #15 terminals are
> the two leads of the primary winding of the ignition coil. The #1 pin
> is connexted to ECU.
>
> I believe the ECU feeds the #1 terminal with the pulsation current, which
> makes the high voltage winding to generate high voltage for the spark plugs.
> This pulsation current then comes out of terminal #15 to feed to the fuel
> pump relay as the power source for the relay.
>
> If for any reason the engine stops (misfires permanently) wheile you are
> driving the van, the Hall sending unit will stop generating the Hall signal.
> The ECU will stop feeding the pulsation current as a result. Consequently
> the fuel pump relay will lose its power from the #15 terminal. As a result
> the relay deactivates and the fuel pump stops. This is indeed a safty
> feature.
> You don't want the fuel pump continues to pump causing fuel line to burst.
>
> As an example, if your van is rear ended by someone, which knocks out the
> ignition distributor and the engine stops. Let's say you pass out from the
> impact from the rear. So the ighition key is still in the on position.
> The fuel pump will stop pumping gas, which may prevent a fire or an
> explosion
> as a result. Basically if the engine stops the fuel pump will not pump.
> When the engine is being cranked the fuel pump will pump because the engine
> is turning.
>
> SDF - no, the fuel pump runs during cranking because of the 'start signal'
> from the key. It's a black/red wire in the black junction box. After
> 'start' ..when the engine is running....yes, then it gets the 'keep the fuel
> pump relay energized' information from the ignition system.
> I believe this to be correct.
>
> If you have a bad ignition coil the fuel pump will not pump. If you have a
> bad
> Hall sending unit the pump will not pump either. If the ECU is bad of course
> the pump may not pump either. I would check the Hall sending unit first.
> Usually
> the only way it will break down is bad connection. I would check the
> ignition
> coil's primary winding. ECU is possible so it would be nice if you have a
> spare.
>
> SDF - for whatever it's worth......in thousands of vanagons I worked on, I
> have never ONCE found a bad hall sensor. I know everybody goes checking for
> that cause it's in the Bentley ....I never even think about it, never find a
> bad one etc. I have all these parts for sale, good used, of course.
>
> Hope this makes some sense to you.
>
> David
>
>
>
>
>
>
>
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