Re: [elec] fuel pump relay/ignition woes '81 16v

["Jonas K." <jkarlsso@metabolex.com>]

Dave Novak wrote:

> So the deal is.. the fuel pump relay doesn't activate (prime the fuel pump)
> when I turn the ignition on. Therefore (?), the ignition control unit
> doesn't get the signal to start sparking when I activate the starter.

Well, kinda. I know we've talked about this before so I won't talk too much
about it, but I just want to make sure that the causal relationship is
understood.  The chain of events goes like this:

The hall sender in the distributor sends a signal to the ICU. (basically there
is a "cylinder" with 4 windows in it (inside the distributor). One window per
spark plug wire. As the distributor turns so does the cylinder, and a the hall
sender picks up the changes in magnetic field caused by the windows.)

This signal causes the ICU (which is basically a big whopping transistor) to
ground terminal 1 of the coil.

This in turn causes the electric field that has been built up in the coil to
collapse, and as it does so, it generates many thousands of volts, enough to
make a spark.

The FPR plays no role in this chain of events. VW decided that it would be bad
to have an electric fuel pump that was always pumping fuel when the ignition
was in the on position. You only need fuel if the engine is turning, and if the
engine is turning, then the hall sender is sending a signal, and the ICU is
grounding terminal 1. They decided to use Terminal 1 to control a Relay.


> I bought a new fuel pump relay from the Pottermeister, and that
> unfortunatley didn't help.

It's always good to have a new one.


>
>
> I know the wire from coil terminal 1 to the fuel pump relay has continuity.
> Every wire going into the relay is doing what it should be. The relay socket
> proves to have hot (30) power, switched (15) power, ground (31), and the
> red/yellow wire has
> continuity to the fuel pump itself.
>
> Never does the fuel pump relay click. the Load Reduction Relay does click
> when I turn the key to "on".

I forget, but what happens when you try to bypass the relay, i.e. remove the
relay and connect terminal 30 to the "red/yellow wire" that goes to the fuel
pump? The fuel pump should run.


Looking at old emails, I see that you said that when you disconnect terminal 15
at the coil (which also powered the CIS-E computer), and turn the ignition on,
the pump runs. But not otherwise.

Let's probe this some more. Try to power just the coil, directly from the
battery if you want, and see if the pump runs, repeat for the CIS-E computer.
See if anything interesting happens.

HTH

Jonas
85 Scirocco 2.0






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