roger1918
+1y
I put my old O2 sensor back in, and it is now running in closed loop with no problems. I was able to adjust the mixture at idle to give dwells in the mid-40's. So the system seems to be working OK. I never disconnected the old O2 sensor while adjusting the valves, so I don't know how it got fried.
Next questions: When I am driving at a steady speed (i.e., load) the dwell stays at zero. It moves off zero when decelerating. Does this mean it is running lean at a steady load??
The e-check guy said a lean mixture could cause NOX problems and mine seems to be running lean to him according to the CO numbers (CO=0). Should the dwell be something other than zero at a steady cruise?? Should I maybe change to a richer jet and let the mixture solonoid adjust things??
Deep questions, I know.
Post was last edited on May 13, 2009 05:05. This post has been edited 1
times.
roger1918
+1y
Dawg: Still working on it, but making some progress.
MT: Since there is only one vacuum operated switch that I can see in the system, I guess this is the one you mean (it is teed in with the vacuum sensor to a line from the manifold). I blocked off the vacuum line to the switch and the result was that the dwell is fixed at zero no matter what I do - idling, cruising, accelerating, decelerating. All this is with a warm engine of course. BTW, I had checked the vacuum switch according to the manual and it is opening and closing at the specified vacuum.
Also, (with vacuum switch hooked up) I am having some trouble with closed loop operation again. At idle it sometimes goes to 27 degrees. If this happens and I blip the throttle it comes out but soon goes back to 27. However, if I speed the engine up to 3000 rpm or so and hold it there for 15 seconds then it will stay in closed loop. Seems like something is affecting the O2 sensor and the high speed is cleaning it again. Does this make sense? I don't know much about O2 sensors.
I'm still wondering if its running at zero degrees dwell at cruise is an indication that it is too lean.
Post was last edited on May 13, 2009 05:05. This post has been edited 1
times.
Post was last edited on May 13, 2009 05:05. This post has been edited 1
times.
roger1918
+1y
MT: I am at sea level here. I have never had the truck in the mountains, but my son was using it for the better part of a year and may have had it up to 3 thousand feet in the local hills. Prior to my owning it I have no idea where the prior owner may have gone with it.
When I opened up the carb I changed the gasket under the heater plate. I hadn't ment to, but it came up with the carb when I pulled it, and tore the old gasket.
My truck idles very smoothly now. I have sprayed cleaner around the carb and haven't found a leak, but I can do it again. I can check more carefully all around the manifold too.
Actually it isn't losing closed loop at higher rpms, it just stays at zero dwell. It's still alive because if I goose it a bit to squirt some fuel in with the accelerator pump the dwell comes up off of zero.
I'll start reading about the altitude compensator (if I can find any info).
Post was last edited on May 13, 2009 05:05. This post has been edited 1
times.
Post was last edited on May 13, 2009 05:05. This post has been edited 1
times.
roger1918
+1y
MT: I'm a little behind you at the moment.
This morning I checked for vacuum leaks. Nothing around the carb, but I found a leak at the manifold/head joint back near the fuel pump.
Since I was going to have to pull the manifold I decided to pull the head too and clean out any deposits. I have completed this project, but haven't run the engine yet. It is late and dark here, and I want to check the routing of all the lines in the light. So it will have to wait until morning.
There was some carbon build up, but it wasn't really bad. Then again, I don't know exactly what "really bad" would be from the point of making NOX.