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Re: Easy Staring with Fuel Pump Prep Run
>Many 80s non-turbo Audis work the way you describe.
>The fuel pump relay is supposed to supply power to the fuel
>pump only run when it gets ignition pulse signals from
>the ignition coil, signifying that the engine is running.
>This is so that in the event the car stalls the fuel pump will
>automatically stop too. When turning the ignition key to
>the on position, the fuel pump relay receives power and it
>is designed to briefly run the pump to pressurize the system.
>However, I have also noted on my 4000 that this doesn't
>always happen. Probably a flakey FP relay. It is an aftermarket
>replacement. The original relay always reliably ran the pump
>after turning the key to on, but I replaced the relay thinking
>it was defective, only to find that it was only a loose connection
>at the relay pin. I threw away the good old relay though :-(.
I have experinced this "flakey" behavior on all BMWs and Audis with CIS--
sometimes FP runs on turned key, sometimes it doesn't... I always imagined
that it has a pressure sensor, and if the accumulator is already up to
press., then it doesn't bother turning the pump on again... Try this by
turning your key to run, then off, then run and off, and so on, usually it
only does it the first time (charges up accumulator?) but maybe a time
delay in the relay???.. Don't know where pressure sensor would be though,
just checked bentley and couldn't find it...