california 60 smog, high CO% low NO no O2 (1 Viewer)

[salvage60]

Thanks much for the encouraging words. This has gone way beyond rational but owning one of these already qualifies that. This truck was my daily driver 15 years ago and now it just does dirty weekend duty and home depot runs. I guess you are right Output Shaft, its just a big boy puzzle and there is the challenge. Big picture is I hope to keep it going long enough to take my 5 year old son on many trips to the desert.

The actual numbers for the last 5 fails are:

I agree about the charcoal canister although I have wondered if somehow it could not be venting the carb bowl, giving pressure and therefore extra fuel.

The big "what if" in my mind is the "computer" but not sure how it would send so much extra fuel. The very close rpm but different speed makes me wonder if some system is being triggered although I would assume the rollers have more resistance at 25 mph.

I did the lean drop per the FSM with the air cleaner off and the HIC plugged, I may see if I can lean it out more with everything assembled. leaning out the idle is the only significant thing I did between the last two tests although I had discounted this due to the off idle test.

I do feel like I am winning the war as I have sealed, tightened, repaired many little things to get it running nice even with the EGR hooked up. the frustrating part is knowing it could be one simple adjustment that makes the difference and there is no way to test the emissions at home.

Thanks again to everyone for all the help.

 

[Pin_Head]

Those are very pretty numbers but without any labels showing what the rows and columns mean, they aren't very interpretable.

 

[salvage60]

Sorry about that, I have a spreadsheet with all the results since I have owned it and had just clipped the current #s off. Here is one with titles, it matches the format of the California smog document.

 

[Pin_Head]

OK, that is better. It is pretty clear that it is just the CO. It seems strange that it just squeaked under the bar at 15 mph but was over at 25. The other thing noteworthy is that at 2%, it is high. There is something way off in the air fuel ratio that the AI/catalyst cannot compensate for because it is so high. You need to fix the primary cause: It is either delivering too much fuel (clogged air holes in the emulsion tubes, high float level, wrong main jet) or not enough air (clogged air cleaner, choke stuck on). The air side is easy enough to check.

Try the "Oklahoma" carb rebuild by spraying carb cleaner all over inside, wait a couple of minutes, start the engine, rev up to 3,000 RPM and then hand choke it (yes, you put your hand over the air horn) until it almost stalls. This pulls a high vacuum high up in the carb, pulling fuel out of the nozzles and air metering holes. Repeat as necessary.

If the Okie rebuild doesn't do the trick, it may be time for a more complete carb rebuild.

 

[cruiserfj45]

I just read through everything and the other thing that is still jumping out is the lac of O2. I would try bypassing the computer and see if that works. You could also have plugged AI injectors in the exhaust manifold due to having a bad check valve this whole time. I think what is needed is more O2 to add to the CO to make CO2.

My last numbers. I haven't hardly touched it for 2 years and just filled it with premium and some fuel additive and drove it down there. The other thing is I only have the 2 speed test, no dino.

RPM %CO2 %o2 HC CO%
877 12.28 3.2 26 .01
2403 13.38 1.7 27 .06



Good explanation of cat operation.


Better pictures of cat operation, cheesy music.

 

[salvage60]

Pin Head, I am pretty sure you are right. The carb has less than 30k on it but it sat for a few years in the garage with a broken transfer case so I would assume it is gummed up. I have tried the Okie rebuild but maybe that's not enough. What is odd is it has passed since it was brought back to life although that was with a brand new cat. The tank has been replace since the last passing test so maybe something was stirred up or maybe just pulling it off and on moved some dirt around to the wrong passages. I was suspecting the cat as it is aftermarket but I ran it hot yesterday and could see by the in / out temp difference that it is working, I think there is just more fuel than it can correct for. Temp diff = burning cat = AI working. I think a carb kit is next.

Pin Head, nice you tube rebuild videos. Those should make it a lot easier.

 

[Spike Strip]

That test from 12/27 shows the AI is still not functioning properly... Should be above 0.5 at a min. Throw a gallon of denatured Alcohol in it next time and get it over with. You'll break out in shingles trying to figger it out...

 

[salvage60]

Well it passed. Not just passed but extremely clean. To close the loop on this I think I finally understand what I was doing wrong. Since the last test I decided to rebuild the carb, I am not sure there was anything wrong with it bu since it had sat a few years in the garage I just wanted to be sure. After I got it all back together I did a little more reading on the "lean drop" idle mix. I am pretty sure I was missing the last step of dropping the idle speed with the mixture screw. Due to the low rpm of the test the idle mix does seem to matter a lot. I had not put much thought in this as I assumed the 15 / 25 mph tests would not notice this. Lessons learned and hopefully some of my troubles can save others some time.

On the freeway it does feel a little asthmatic but still has plenty of power. I also noticed with everything operational and tuned per spec the EGR does not have the usual stumble upon acceleration.

I did consider adding alcohol but prefer that for drinking and whats the point in doing a puzzle if you just cheat.

Thanks again for all who have helped and this board for being a wealth of knowledge.

 

[Output Shaft]

You did it! Congratulations. Those numbers are really low. That's great.

 

[Pin_Head]

Congratulations! It is blowing very clean. The moral to the story is fix the primary cause and don't look for a band aid. Carbureted engines don't like sitting for long. This didn't have anything to do with the idle setting because the tests are at around 1600 RPM where the idle circuit is no longer in play.

 

[nfranco]

Congratulations! Feels good doesn't it!

 

[salvage60]

The lesson I feel I have learned is the idle circuit does come into play if the parameters of the test require a very low RPM. The second to last test where I passed the 15 MPH all I had adjusted was the idle mix leaner and it passed at the higher RPM (lower speed). Doing the carb rebuild I did not see anything really wrong but I at least ruled out a clogged circuit. My theory on this is that at a low RPM the idle circuit represents a much larger percentage of the fuel and therefore the mixture is important. For some reason due to old age, OCD, and ADD I was not doing the final lean out of the idle mix with the mixture screw and am now convinced this was the real problem. The bonus on all of this is it is running better than ever even fully smogged.

 

[Output Shaft]

My theory on this is that at a low RPM the idle circuit represents a much larger percentage of the fuel and therefore the mixture is important

Very correct. The influence of the idle mixture never "goes away". It only diminishes proportionately as the throttle plate opens up. Thanks for following up. Good stuff.

 

[Pin_Head]

Allthough the idle circuit always provides fuel, the idle mixture screw is out of play as soon as the throttle opens a few degrees and starts pulling fuel out of the transition slot, which sits just above the idle screw. At that point, there is no more fuel at the screw.
However, at 1,600 RPM, it is the main jet that is providing the vast majority of the fuel.