Date:         Wed, 12 Nov 2003 11:58:49 -0800
Reply-To:     mark drillock <drillock@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         mark drillock <drillock@EARTHLINK.NET>
Subject:      Re: can a locked fuel pump kill an ECU?
Comments: To: Austin <austins@IX.NETCOM.COM>
Content-Type: text/plain; charset=us-ascii

Don't blame the ECU yet. The ECU only runs the pump for a few seconds
when the key is first turned on. You have to measure the voltage during
that few seconds. Otherwise, the ECU turns the pump back on only when it
knows the engine is turning. It knows it is turning when it see hall
pulses from the distributor.

It is for safety reasons that the ECU turns the pump off when the engine
is stopped.

Mark

Austin wrote:
>
>   I go out to start the bus ('87) & after running for ~10 seconds it
> dies.  Finally trace that the fuel pump is locked, won't turn at all (yeah
> I shoulda installed a filter between the tank & the pump long ago).  But
> now the weird thing is that there is no 12v to the pump!  Disconnecting the
> ECU & bridging contacts 3 & 13 of the connector to the ECU (per Bentley)
> there is solid voltage to the pump leads - & obviously the 2 relays in the
> black box over the coil work fine.  Re-connect the ECU & no voltage to the
> fuel pump relay, or of course to the pump itself.  Not being an EE the
> limit of my electrical trouble shooting abilities is to open the ECU & the
> idle stabilizer unit (the box behind the right taillight) and checking for
> cold solder joints. NADA.  Is it possible that the locked pump burned out a
> transistor or something else in the ECU that should be switching voltage to
> the pump?
>
> Austin