[Diy_efi] Re: Diy_efi digest, Vol 1 #327 - Dying Porsche

[Bill Washington]

Mike,
    Check your tachometric relay and the inputs to it - it supplies 
power to your fuel pump.
At startup it suplies power to the pump but then relies on regular 
pulses (ignition I think) to keep it energised. It's purpose is to stop 
the fuel pump in the event of an accident.
Regards
Bill

>--__--__--
>
>Message: 7
>Date: Sat, 26 Oct 2002 17:33:31 -0700
From: Mike Sharp <Mike_Sharp at pacbell.net>
>To: diy_efi at diy-efi.org
>Subject: [Diy_efi] Bosch DME trouble...
>Reply-To: diy_efi at diy-efi.org
>
>Hi,
>
>In case you missed my last email...
>
>Porsche 924S, Bosch L-Jetronic w/Lamba control, Motronic
>The car starts and runs reliably (its drivable) for the 15-20 seconds it 
>takes to switch from
>cold-start to warm-up mode.
>
>Per the Porsche shop manual:
>  . grounding all around the system has been verified
>  . Power to the DME control unit is correct
>  . Fuel pump runs
>  . The speed and reference mark transmitters have been verified via 
>'scope and have sufficient signal strength
>  . Temperature sensors I & II have been verified via resistance checks
>  . The throttle switches (both throttle closed & wide open switches) are OK
>
>What does look out of spec are the voltage readings on the air flow 
>sensor.  The shop manual says >8V across pins 9 & 6 (with the flow 
>sensor & motronic connected) on the Motronic.  I've got 5.5V.  I swapped 
>out both the flow sensor and the computer for other good units and the 
>resutls are the same.  I verified that the harness between the Motronic 
>and the air flow sensor aren't shorted or corroded.  With the hardness 
>disconnected at both the airflow sensor and the Motronic the resistance 
>plug-to-plug is minimal (a couple of ohms) and resistance between pins 
>is infinite so I can't account for the voltage difference relative to 
>what the shop manual says.
>
>So what am I missing?  
>
>    --Mike
>
>  
>



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