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post #1 of (permalink) Old 10-07-1999, 09:58 AM
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Hey dorfs again!

Firstly, thanks to xyj173 for the suggestion. All air cleaner related attachments have been checked and are operating properly, except for the faulty air injection tube.
Now dorfs - curb idle and fast idle have been set to specs. I tested the pull off by disconnecting the hose and after gently pushing the diaphram to it's seat with my finger, I placed another finger over its vac inlet hole. The acid test here is if the diaphram holds, then it is still in working order, which it is.
Now - with the engine cold in the morning, I took the air cleaner off and watched the choke plate. I hit the throttle once and the plate closed as designed. The idle screw was on the second step of the cam. I then started the engine and immediately the pull-off went to work and backed the plate off to specs as designed. Then the "event" began again. The engine began struggling, almost as if smothering itself. I tried moving the plate to see what would happen, but that didn't help. Then it killed as I knew it would. It seems reasonable that if the check valve on the exhaust side is not working, that exhaust gas would back up into the carb, but I can place my finger over the hole and there is almost no movement of air at all. But I'll replace that right away anyway. I might get lucky. -- Wait a minute, it just occurred to me that the problem still occurred, even with the air cleaner off, hence, the air injection tubes were not in contact with the carb, and not subjecting the carb to exhaust gas. What now?

By the way, you mentioned my Oxy sensor forcing the carb rich, but I did the Nutter computer by-pass last week, so it should be having no effect on the rich/lean mix, right? Also, even though I don't want to polute the air, emission inspections have not made it to Louisiana yet. The stupid emissions system is what's causing my pipes to billow black smoke in the first place.

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post #2 of (permalink) Old 10-07-1999, 11:24 AM
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Re: Hey dorfs again!

You never know when Dorfs is going to swing on by, so I'll chime in. I missed the earlier posts, but it sounds like you are
running rich. I assume you already verified the idle tubes were not pour fuel out, so have you looked at spark? How
do the spark pulugs look? Any wires arching out? Strong spark?

Terry L. Howe http://www.off-road.com/~txh3202
post #3 of (permalink) Old 10-07-1999, 04:38 PM
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Re: Hey dorfs again!

You may well be on the right track with this problem being exhaust gas related but not from the air injection tube. Maybe it is the EGR valve. It could be stuck open. The valve is not supposed to be open when the engine is idling cold. Check it out and Good Luck!

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post #4 of (permalink) Old 10-07-1999, 08:59 PM
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Re: Hey dorfs again!

Let me see if I get this straight, cold in the morning with the air cleaner off, you set the choke. Then started the motor on high idle. The pull-off opened the choke, then it began to flood and billow black smoke. As this was happening, did you take your finger, and open the choke a little more? If it is still billowing black smoke, try standing the choke plate almost straight up, as no choke, and see if it still dies.

The only other thing that I can think of is a grossly mis-adjusted float level, but kind of ruled that out, as you said it runs good warm. The Nutter bypass shouldn't effect the cold drivability that much, as the feedback circuit in this carb is only about 10% of the mains.

The choke pull-off demination for these carbs were given with "drill guages" measured from the choke plate to the air horn. The Carter BBD2"s have a bad tendency to warp, or egg shape the air horn if the wing nut that holds the air filter housing was over tightened. This changed the measurement of the choke angles. Newer methods are to use a level guage set to zero degrees with the choke totally closed. The new spes is something like 22 degrees open for the pull-off, and 32 degrees for the unloader. I live at high altitude, 7500 feet, and found it mecessary to add almost 10 more degrees.

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