Sure you can.

I'd use the Capture mode of the CCP modules using Timer1, for the ON time.

Timer 2 can be the timebase used to count the speedometer pulses on the INT (external interrupt) pin.

And the same signal from the Injector can be fed to T0CKI, so Timer 0 can count the RPM's too.

Speed, Distance, Consumption and Tachometer.
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