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No Power Off Idle; engine troubleshooting
Topic Started: Sep 16 2009, 07:12 PM (1,068 Views)
Paul
Member
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My 1959 3B (71k miles) has been sitting for about 2 years with only occasional starting. I can start it easily and it idles well with about 19 inches of vacuum but on acceleration it stumbles and surges, and after a few pedal pumps catches, but will not run up smoothly and occasionally backfires through the carb. When I tried to drive it had so little power that I had a difficult time getting it to move - I had to keep pumpiing the pedal to get it to rev up so it could move.

Compression is uniform but maybe a bit on the low side. Timing and dwell are set correctly. I could screw in the mixture screw with little change, if any, until it was completely in when the motor threatened to stop. The carb is a Carter YF OEM replacement about 15 years ago. I had overhauled the carb last spring but was not too sure if the kit was appropriate (from one of the jeep suppliers, not a local parts store) as the idle jet was different-sized than the original. I opted for the original after I had problems with the running and it got me back to a reasonably decent idle.

I wondering if I got the carb completely clean. My only tools are the spray can of carb cleaner and a small air compressor. I had the fuel pump diaphram self-destruct prior to the overhaul and wonder if some fragments migrated into the carb. I tried to reverse-purge the passages but the poor performance is making me think I missed something - some of the passages in the throat are difficult to access.

Am I looking in the right areas or is there something else I need to check?


Thanks, Paul
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COPPERSWILLY
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Copperswilly
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I would say you might need to rebuild your carb possibly a new fuel pump and maybe a new fuel filter...I had that type of problem after I pulled my 54 out of an 5 year down time. Also if your charging system isn't putting out enough voltage you may have a week spark which can cause loss of power. It will be fine at idle but when you try to rev up it will bog down, good luck
Chris .... MD
54 cj3b OIIIIIO
62 cj3b OIIIIIO
74 cj5. OllllllO
49 Bantam TC3
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jyotin
Member
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If the jeep has been sitting, try adding some Lucas fuel treatment/injector cleaner. It'll clear out any water and also compensate for old fuel. Now I know the jeep doesn't have injectors, but this stuff works wonders on both diesel and gasoline engines, with or without injectors.

I use it in my jeeps as well as my truck and tractor.

It doesn't hurt to add more than what they call for, so I usually add at least half again to what they call for.

I'd try this before I even picked up a wrench.
It's just my luck that something good is going to happen to me today.
54 - 3B - down on the farm
67 - cj6 - former state of Alabama vehicle
?? - cj5 T98a - made from spare parts - Ford tractor blue
?? - cj5 T98a - made from spare parts - Jeep green
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dos equis
Member
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try fresh gas this gas we get now looses i octain quikly causes poor running in my small engines and motorcycles
1953 willys cj3b,1998 4.3 chev vortec v6 fuel injected,1965 sm 420 trans,11.5 gm clutch, 538 diffs,11x2 brakes,950x33x15 super swampers on 15x8 rims with 2 inch backspace,saginaw power steering,
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HOGHEAD
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Old Jeep Fart
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I had a V8 in a cj-5 once that did a nose dive when you came off the line ,, then it would explode & run,,, I replaced the accelerator pump in the Holley & it was back to just over 3 seconds in 300 ft,, :rolleyes:
Dargan Md...
Death Before 2 Wheel Drive...
"On a Steel Horse I ride"
AMC Rules.
"Journey" not the Destination...
59 Cj3-b (married to a 74 Cj-5 frame & AMC running gear)
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Willys Overland,,

My Build http://z4.invisionfree.com/CJ3B_Bulletin_B...?showtopic=2892
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oldtime
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MODERATOR
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Can you pull the spark plugs and describe what you see via visual obsevation.
Describe coloration, texture and condition of electrode.
Is the ceramiic sooted or clean and white ? And so on.....
I'll go look for my thinking cap ..........
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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Paul
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Thanks for the replies so far. I did try the gas drier today and while it started and idled well with some surging, it still would not freely rev up without hesitation, backfiring throught the carb occassionally, and overall weak in power. To get this I had the choke on about half and seem to have to pump the gas to get it to rev up when it stumbles. I had the mixture screw out to about 2 turns and on reading the site here, closed it to about 1. It ran for about 15 minutes before I shut it off.

I pulled the plugs that are fairly new and they are coated with a thin carbon soot layer. The electrodes look OK - not pitted or anything.
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dos equis
Member
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have you checked for a vacuam leak,that would foul your mixture and make it run lean which might be the cause of the backfire.
1953 willys cj3b,1998 4.3 chev vortec v6 fuel injected,1965 sm 420 trans,11.5 gm clutch, 538 diffs,11x2 brakes,950x33x15 super swampers on 15x8 rims with 2 inch backspace,saginaw power steering,
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Paul
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I get mixed results. When it is idling smoothly it sits at 19" but when it surges, it drops. Today it was idling really slow (guessing 500 rpm) and I had 15". When I press on the gas (in neutral) it speeds up and then stumbles.

I did replace the gasket on the exhaust valve cover and cleaned the crankcase ventilation valve that leasd to the T below the carb. The carb gasket was new and it is cranked down pretty good. The carb is about 15 years old and has seen only about 15k miles - my old one leaked along the throttle plate shaft. If there is a vacuum leak, I cannot seem to locate it - Any common areas to check on these F heads?

Could it be possible that the high-speed circuit plumbing might be clogged given it starts to rev and then stumbles and that it seems to run slightly better, though rich, if the choke is pulled???
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oldtime
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MODERATOR
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Paul from your description I am thinking you need to look into this:

http://www.film.queensu.ca/CJ3B/Photos/Tec...Bulletin454.JPG

http://www.film.queensu.ca/CJ3B/Photos/Tec...YFBulletin3.JPG

( click the lower right to enlarge the bulletin )

I suggest you run the jeep a minute or so before removing the air horn.
Please note the fuel level within the fuel well after air horn removal.
That will help to determine other potential problems.
Next give the pump discharge check ball/valve the 60 second test.
The accelerator pump discharge is regulated by either a ball and weight or a needle type valve.
I suspect yours is equipped with a pump discharge check valve.

Let us know what you find.
Also please indicate the carburetor model number that should be stamped upon the side of body webbing.
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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