RE: [alfa] Dead GTV-6, stymied mechanics

["Peter Webb" <webb.p@xxxxxxxxxxx>]

> JEFF AND ALL See answers below, but one question--does the timing
> control unit affect the injector pulses??--we do have spark back now.

Yes, all batch type EFI systems require tach signal to know when and how
much fuel to inject.

Tach arrives on pin 1 of the ECU.   It's hard to tell if you're getting
signal there without an o-scope.   If you mechanic has access to one, it
will show you RPM.

The AFM wiper arrives on pin 7 of the ECU and leaves from pin 7 on the AFM
connector.   You should see varying 0-5v on those pins.   IAT leaves on pin
27 of the AFM connector and arrives on pin 27 of the ECU connector.  You
should see about 13k resistance at 70degF so you can scale from there.

The actual IAT sensor is in the AFM right before the door in a little white
nub.

The hall sensor works on a negative field effect cross current of the
sensor.  IOW, there's a constant 5-12v current across one field where a 5v
field is generated perpeducular to the constant field on each pulse,
disrupting the constant field causing the 'hall effect'   This is sent to
the spark ECU which in turn grounds the coil and forces it to discharge.
The Hall trigger is sent to the fuel ECU to tell it when to fire, and how
fast the engine is turning.

The fuel pump is activated from a microswitch inside the AFM that has a
brass tab that bends away from its connector when the door is fully closed.
It sends a signal to the ECU and de-energizes pin 88a, 88b and 88c of the
combi-relay for the injector 12v and 86b for the fuel pump through pins 36
(fuel pump) and 39 (injectors) of the AFM connector.   The ECU energizes the
combi relay with ignition on through pin 28 of the ECU to pin 85 of the
combi-relay.

Hope this gives you a few things to test.  Email me off-list I can send you
the L-Jet wiring diagram and other handy documentation I have on it.

-Peter
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