Low Voltage in Injector Circuit

[Jandrix]

Hey Folks,

I've been attempting to correct some high fuel trims on my '97 RT/10 that only occur at idle and very light partial throttle (+15-20% trims).

I have found that I've consistently got about 1V less at the injectors than what the battery / generator are outputting, whether running or not.

The lower voltage is present in the entire circuit which is fed by the output of the Automatic Shutdown Relay. If I disconnect plugs C107 and C111, which provide power to the upstream and downstream O2 sensor heaters, then the voltage in the circuit returns to the same as the battery / generator. The upstream O2 sensors are brand new, the downstream sensors may be quite old, I don't know their age.

Is this normal behaviour? I'm not sure as I'm not the best with electrical issues. The oxygen sensor heaters are certainly drawing current, is the voltage drop of 1V in the circuit reasonable when it is powering the heaters or could this indicate a problem that needs to be further investigated?

Thanks for your help, let me know if there's more info that you need. If I'm content that this is not an issue I'm going to be sending the injectors for cleaning as my next action to attempt to correct the fuel trims.

Cheers

[Viper Specialty]

Normal.

Very long wire run. With 4 O2 heaters dragging on that circuit, it is totally normal to see a voltage drop.

Make sure you are using OE sensors. The heaters in G1/G2 sensors are designed for constant duty as the circuit is not PWM controlled like G3+.