Actually, turning on the ignition only starts the ECU. The ECU then runs
the pump for a few seconds to bring up the fuel pressure in anticipation
of engine starting. From that point on the ECU runs the pump whenever it
see pulses from the hall unit in the distributor.

The ECU does not run the pump directly as that would be a large current
load on it. Instead it controls the fuel pump relay and that relay
provides the current for the pump.

On 1.9 models turning on the ignition also directly provides power to
the fuel pump relay coil but this does not turn on the relay. The other
leg of that relay coil is connected to the ECU and the ECU uses this leg
to enable or disable the relay.

On 2.1 models turning on the ignition turns on the ECU relay which
powers up the ECU and provides power to the fuel pump relay coil. As on
the 1.9, the other leg of that relay coil is connected to the ECU and
the ECU uses this leg to enable or disable the relay.

As no year was referenced in the prior posts I am assuming waterboxer
FI.

Mark

Doug Alcock wrote:
>
> Hi Dave,
>
>         Turning on your ignition starts the fuel pump --- nothing to do
> with the ECU (which, incidentally is Electronic Control Unit --- not
> "Emission" ---- it's the computer that controls the Fuel Injection
> system). Here's a link to the Bosch Fuel Injection Manual if you're
> interested. http://www.conservatory.com/vw/manuals_nyx/L-JetronicWithLambda.html
>
> Cheers,
> Doug
> (Just down the road from you in Mississauga ON)
>
> >Does the ECU control the fuel pump? as in .. does it
> >tell it to turn on when the key is turned to on? ..if
> >it dosnt what does.. ?
> >
> >=====
> >Dave Vieira
> >Hamilton, Ontario
> >Canada