Carb help one barrel clean, one dirty

[WestSlopeCruiser]

My 72 fj40 has been running rich.... sooty exhaust pipe, gassy smelling exhaust, grey smoke when starting with warm/hot engine, hard to start hot (gotta pump a lot of gas to it), easy starting cold, poor performance under load/acceleration, some backfiring when at highway speeds, fuel economy is bad...around 12mpg. It idles and runs fine at slow speeds. I've regapped points, installed new fuel filter and new plug wires, new distributor 5K ago, have not rechecked timing since the new dizzy was added. Could the coil be bad? Vacumn leak?

When I look into the carb, one barrel is clean as a whistle, the other is black, sooty and oily at the bottom. What could cause this?

I've done some searches and it appears it might be the secondary diaghram. Can this be fixed without doing a entire carb rebuild? I have no desire to try a complete carb rebuild and am considering sending it out or trying the Trollhole import carb, if indeed the carb is the culprit.

I have the stock Aisin carb on an unaltered F engine and to my knowledge the carb has never been rebuilt. The truck has 130K on it.

I'd appreciate any advice. I'd like to make sure it's the carb before I rebuild or replace it. Related question... would desmogging help? I'm in western Colorado at about 6000 ft elevation and take trips regularly up to 8-9000 ft.

 

[Pin_Head]

Gas mileage is normal.
Sooty primary is normal.
Never pump the carb on a hot engine to start; it will flood.
Coils rarely fail and if they do, they don't run.
Manifold vacuum leak usually means a bad idle.


What do you mean by "poor performance"? More details about the symptoms and circumstances would help.

Is it backfiring out the exhaust or the carb?

 

[FJforty]

I would get a timing light and verify timing and the advance.

 

[IDave]

Are you using ethanol gas?

 

[kurtnkegger]

It's easy to check your spark from the coil, if it's weak, coils are cheap, and and simple replacement. Did you replace the plugs when you did the wires? Also did you replace the high tension wire from the coil to the dizzy?

 

[WestSlopeCruiser]

Gas mileage is normal.
Sooty primary is normal.
Never pump the carb on a hot engine to start; it will flood.
Coils rarely fail and if they do, they don't run.
Manifold vacuum leak usually means a bad idle.


What do you mean by "poor performance"? More details about the symptoms and circumstances would help.

Is it backfiring out the exhaust or the carb?

It's backfiring out of the exhaust. By poor performance I mean it doesn't have the power on acceleration or hills that it once did. I did notice that the points were closed and I adjusted them to 0.14. It hasn't backfired or stumbled since.

If I don't pump the gas pedal when it's hot, it wont start. Plugs are only 5K old. I pulled 1,3,6 and they were white. I do use ethanol gas as it's the only choice here. I haven't checked the timing, I guess that's next.

 

[Pin_Head]

1. Backfiring on engine braking may be due to the throttle positioner on the carb not functioning.
2. Poor performance. Do a complete tune up according to the FSM. Make sure that the centrifugal advance is working and verify the operation of the mechanical secondary in the carb.
3. Pumping on a hot engine is counter productive for hot starts. Instead hold the pedal down all the way, but do not pump it until the engine starts.

 

[WestSlopeCruiser]

How do I verify if the secondary is working?

thanks pinhead!!

 

[primer7]

I had similar issue with my 1bb on my 69. Sooty exhaust, rich gas smell, sent carb to Mark he found it was warped. The rebuild did the trick and I passed smog on the first try. Bottom line - vacuum leak.

 

[WestSlopeCruiser]

How long did it take Mark to get the carb back to you?

 

[Pin_Head]

How do I verify if the secondary is working?

1. Use your hand to rotate the shaft and make sure that the linkage isn't binding.

2. Remove hood so you can see the carb base and observe the opening of the secondary while the pedal is to the metal going up hill. Alternatively, you could duct tape a video camera to record this area.

 

[WestSlopeCruiser]

If it is the secondary, can I fix it w/o doing an entire carb rebuild? I mean, is it easy to get at or buried in the bowels of the carb?

 

[WestSlopeCruiser]

I just took it up a hill and floored it. It coughed and sputtered like crazy. Seems like the secondary. I'm gonna try to clean/lube the linkage and see if that helps.

 

[WestSlopeCruiser]

In the process of lubing the mechanical actuator and manually depressing the linkage, the throttle cable came off. I finally got it back on, but now the slow idle set speed is really fast. I can't get the idle speed to come back down.

I ran it back up the hill, and no sputtering, but now I'm racing the engine at idle. Could the secondary have gotten stuck open?

I'm a carb newbie and know I really know it!!! Any ideas on why I'm racing at idle and how to fix it?

 

[Pin_Head]

It coughed and sputtered like crazy.

This sounds more like a fuel delivery problem and not a secondary that isnot opening.