Air/Fuel Gauge

I have had trouble making my air fuel gage work from day one. I went through 3 gauges with each having the same problem. The Sunpro CP8210 gauge would light the far right green LED solid and the far left red LEDs would flash. I double checked the point that I tied into the Oxygen sensor and replaced the Oxygen sensor. Same problem. Today, I welded in a new bung and installed a Bosch single wire Oxygen sensor (BCH11027), ran all new wire inside split loom, installed my 4th air fuel gauge and started the truck. It took a few seconds for the truck to heat up and now I have lights. My question is, what should I see? While idling, the gauge is mostly green and when I rev the motor, the gauge swings back and forth. All of this testing is with gasoline. All input would be appreciated. Thanks Pat

The above is the reaction on all the gauges I have used . The gauge swings back and forth on gasoline .

Out the door and back to the hay field to burn some more wood .



Thanks for explaining how the air/fuel gauge worked.


Thanks for the information about the moisture meter. I picked one up at harbor freight for under $15 and it works great.


Hey DanielH
On an OBD duel bed catalytic gasoline system to rich/lean/rich/lean force is intentional. They could only go to this level of sophistication with high speed feedback precise computor fuel control.
This exhaust surplus oxygen loads the one stage of the cat for better oxidization. Then the rich swing gives it the surplus intentional HC fuel to burn for heat and to keep the endothermic reduction section heated and maximum functioning.
These swings are called “crosscounts”. Need to cycle, and detect success at a minimum of 3 cycles per second to show the computer that it IS in fuel control.
Woodgassed; in continuous fuel feed expect to trigger “Check Engine” light and codes directly, and indirectly for overriding the computer’s expected rich/lean fuel cycling control.
OBD I and early OBD II’s up into ~2004 on Chrysler/Dodge/Jeep - just keep driving. Post 2003-07 depending on the model expect the computer to be programmed to Freak! and start going into an emissions fail-safe engine rolling cylinder deactivation “limp-in” mode to force you to crawl in to a shop.
Steve Unruh

Thanks for the info