Call for Carb/HAC Diagnostics

[jwest]

These are results from two emissions tests. The first shows a rich condition (high CO which then kicked up the HC). The bottom test shows a very clean pass. Note the extremely low .02 CO%. Also note, however, that the low CO% is a direct result of a pulled circuit shown by the bottom most jpeg.

This is a new HAC valve. Motor is healthy, well-tuned and all other systems check. The carb was rebuilt 2 years ago.

The pulled circuit creates a leaner condition, but what's causing the problem?

Also, is the circled circuit on the illustration below, the primary high speed or the secondary high speed circuit?

** As long as we're on the subject, I'm curious as to whether "max" allowable emissions figures are the same nationwide. These figuers are California which I have a hunch are tighter. Anyone from other states care to look up their "max" allowables?

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[dallen341]

I just went through this on my 60 here in California. The emissions standards have gotten more strict as the years go by. Seems that the goal is to get the older vehicles off the road. I assume that when you pulled the HAC circuit you left the port on the carb open causing a lean condition. A few years back I had to rejet the carb and lean it way out to get it to pass the CO part of the test. Catch is too lean causes NO to go up if I recall.

Don

 

[60wag]

The tubes you pulled are the aux air bleeds for the HAC system. Over 4000 ft the HAC should open those up to add extra air. Below 4k they are closed. What altitude are you at? The CO2 and O2 went up in the second test, that makes sense with the bleeds open. I don't know why you engine would run that rich with them capped except that I've heard that 2Fs run rather rich on cyls 3 and 4 to keep cyls 1 and 6 from running too lean - uneven intake manifold distribution. You could try running with the air bleeds open for a while and then check the plugs in 1 and 6 to see if they are too lean. If so the I'll bet you carb is fine and the appearance of a rich running condition is due to a weak air injection system not oxydizing enough of the CO.

 

[NocalFJ60]

Your timing set with both lines disconnected from dizzy? You could put a vacuum guage on the line going to the outer diaphram on the diizzy and make sure it does not get vacuum while reving up the engine.Maybe something is wrong with the new HAC valve and it is opening some to change the timing.

But I guess that would not change why it runs leaner with more air to the carb. Maybe some other system in carb is not getting enough air.

 

[jwest]

The port was left open during the test. Don, aren't you running hot with the lean jets?

60wag, we're at 865 ft., sea level basically.

Let's say that air/fuel is fine but air injection isn't cleaning it up. Yet, with everything connected properly, performance and mileage decrease.

In other words, how is it that the new HAC and running with those 2 circuits plugged (not connected, nor open ...but plugged), improved performance and gas mileage? HAC shouldn't be feeding air at sea level anyway, yet what accounts for the improvement with the circuits closed off? Any harm in running this way? Seems like the 2F likes running on the rich side.

Something isn't right.

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[dallen341]

The port was left open during the test. Don, aren't you running hot with the lean jets?

I reversed the re-ject after getting it smogged. It now has stock mains in it.

Don

 

[jwest]

ttt

 

[60wag]

I'm a bit confused. Do I have this right?
You have three different conditions:
1. Both air bleed tubes properly connected resulting in poor emissions, decreased performance and milage.
2. Both, or at least the primary tube disconnected at the carb resulting in big drop in emissions.
3. Both air bleeds physically plugged off, capped or otherwise totally blocked resulting in better performance and milage.

I'm stumped. At you're altitude, the HAC should keep those two ports capped off as if you had stuffed BBs in the hoses. With the engine running, try sucking on one of the bleed hoses headed for the HAC. Is it closed, or open to atmosphere? It should be closed. Either way, the emit test results with the hoses connected don't indicate a leak. Did you change the HAC after the first test?

A lean running condition can develop more power but is hard on the engine. Do you get any knocking under heavey load? Also check out the NO numbers between the two tests. The lean condition made the NO jump up.

Its the difference in milage between 1 and 3 that has me puzzled. You might want to check the hose routing one more time, especially the ones at the carb base near the valve cover.