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Date:         Tue, 19 Jul 94 15:57:23 PDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         David.Kao@eng.sun.com (David Kao)
Subject:      Re: Failing Fuel Pump?

I looked at the schematic of my bently manual. If the ECU wants to turn on the fuel pump it grounds the terminal #3, which is connected to 85 of the relay, and therefore the relay is activated. The pump should be buzzing.

Also, this terminal #3 also grounds all 4 injectors together with the pump relay. If the ECU can not ground the #3 terminal, not only the pump won't buzz, all injectors won't feed engin gas either.

Check the big ECU connector for dirty/oxidized contacts, especially the #3 pin. In case the ECU is indeed not activating the pump relay and all 4 injectors then you have a real problem now. You may want to open up the ECU box and trace the #3 pin wire into the box. If the wire is driven by a transistor, instead of an IC, then it's likely the transistor has been over loaded/heated and determined to quit. If true then replacing the transistor is likely to fix all.

There should be a 1 - 2 second buzz from the fuel pump after turning on the ignition switch (to the 1st stop, not cranking engine yet). This is a quick check of the fuel pump operation.

David

----- Begin Included Message -----

- check terminal 86 of fuel pump relay for battery voltage; check terminal 30 for battery voltage. - remove fuel pump relay and check terminal 85 (in socket) for ground from 3 of ECU while cranking. if not: check continuity of wire from terminal 85 of fuel pump relay holder to terminal 3 of ECU. if continuity is ok, replace ECU.

hope it helps. joel

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