IIRC, the fuel injector looks just like a solenoid to the car computer.
 You should be able to see a nice, clean 12v pulse (with perhaps voltage
spikes when tunred off) on the wire.  I'd use the optocoupler circuit
anyway, though, for a number of reasons.

Are you going to publish the circuit bits for others to use?  I've been
interested in making a fuel usage guage for years...

-Adam

Impakt242@AOL.COM wrote:

>Hello everyone,
>Now that i have decided on a PIC for my dashboard/logger circuit, i would
>like to ask if anyone out there has a circuit which can interface a fuel
>injector pulse signal to a PIC input?
>
>I have found the circuit to interface it to the points, or coil output of the
>car, but nothing so far for the injectors.
>
>Can the same circuit for the points be used for the injectors? I have seen
>one example on diy-efi using optocouplers, there has to be another way
>though.
>
>Te circuit would connect the injector pulses to a PWM Capture pin on the 877
>to measure time high and low and show the pulse width in milliseconds, and
>also show duty cycle.
>
>
>Daren
>
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