LM not reading O2 correctly- looking for ideas.

[86Shelby]

This weekend I had some time on my hands and installed an old Dawes Device O2 gauge in the Omni. I was alarmed to see that it was reading red & yellow the vast majority of the time; even while cruising in closed loop. Hook up the OTC and see that the O2 signal is only showing .6V at the max, normally around .3-.5V occasionally dropping down to 0V. I back probed the O2 connector with a DVOM and it also showed .8-.95V regularly, sometimes dipping down to .5. I used the Neg. battery post as the ground for the DD and the DVOM.

Am I on the right track to think that I have an issue with excessive resistance in the O2 signal wire? Or perhaps a LM ground with a little too much resistance which could raise the voltage threshhold for the O2 to read correctly?

Being that the engine is constantly running rich would explain my sudden drop in fuel mileage after the engine & tranny swap, I did use a brand new O2 3 wire sensor. I went from 24-25 MPG in town down to 15-16 MPG. It was a 2.5, +40s, GLHS LM, A-555. Now it's a 2.2, stock injectors, GLHS LM, lockup A413 with a TBI 2200 RPM stall converter(it was boxed wrong ).

[turbovanman²]

Whats your fuel pressure?

Use this to check/verify the sensor-

http://www.turbo-mopar.com/forums/vb...e&articleid=22

[86Shelby]

56 psi static using a stock regulator.

[86Shelby]

Turns out that most of the problem ended up being a filthy connector at the injector harness .7 ohm resistance between the LM and neg terminal on the battery; .6 ohm from the LM to the fuel rail bolt where it grounds. Cleaned it up the best I could with a towel and electrical cleaner and now it's reading the full range, 0-.9V. It's also cycling MUCH quicker and I'm down to .1 ohm resistance to the fuel rail bolt. I need to rebuild that injector harness since the wire insulation is cracking on several of the wires.

[turbovanman²]

Awesome, glad you found it,