My Carter WO might have to many problems to fix...?
Jul 26, 2020 0:11:08 GMT -5
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Post by tim on Jul 26, 2020 0:11:08 GMT -5
Greetings! Long story coming up, with lots of me banging my head on a wall in frustration. (I found the wall stud at least once, so... ouch.) I apologize in advance for being long-winded, but could use some advise, even if that advice is just telling me its time to send my junk in for a professional rebuilt...
I have a Carter WO (636S-SA) carb on my CJ2a/L134. Engine is a fresh rebuild, & I paid (another) shop to make sure the mechanical timing was set. Starts and runs very well, but I had lots of backfiring upon acceleration and no power. I rebuilt the 636-SA using the basic $30.00 rebuild kit, after spending lots of time watching your videos from this site, and advice from the CJ2A web pages. Then I pulled it apart again, & then again, & again... I just could not get it to stop the backfiring or make any power. At the same time, I have a junk military 539-S carb I was pulling apart to practice and compare with my 636 (because I'm paranoid about losing parts & forgetting where they go...). So I then stripped all the new parts kit/bits out of the 636S and rebuilt the old 539. Still didn't fix the problem, so I pulled BOTH carbs apart into tiny pieces, & used the best bits from that big pile to rebuild one that is "mostly" a 539. This final rebuild fixed "most" of the backfiring & I can get the jeep into 3rd gear now. But even with the 539 carb, it still has no power, takes forever to accelerate and caps out at about 30mph on a flat road. When driving, it now will hesitate/stutter at about 1000-1200rpm (just before I feel the need to shift) but not when sitting still (in neutral I can rev it to almost 2000rpm).
Vacuum tests out at 22 pounds (idle) and 5 pounds (hard acceleration). I live at 5000ft elevation. Gauge has a slight flutter (+/- one psi) which I think is due to the engine builder not replacing the valve guides.
Fuel pump is a AC 577-C-066 putting out 6psi (with a 1/4 inch spacer). Fuel line has a pressure regulator on it, set at 3.5 pounds.
New (modern) distributor, coil, spark plugs and wires. Engine now has 3-4 hours of run time since its rebuild. Spark plugs look good. 12 volt conversion, but I've only got a single-wire alternator right now.
PCV valve is cleaned & tested good. Exhaust is old & rusty but clear of obstruction. compression is good in all 4 cylinders.
So here is the weird stuff I can't seem to fix or figure out:
1) No matter how I adjust the timing (rotating the dizzy) I can't get rid of the "putt-putt-putt" coming out of the exhaust. But the engine seems to run smooth at idle. Even at 200rpm(bottom choke valve just cracked & adjustment screw all the way out), it still idles smooth as glass.
2) Twisting the low speed idle screw (fuel-air mix) does absolutely nothing. Fully tight has no effect on the idle, compression or engine sound. Max lean should stall the engine, so how is that even possible? Also turning the screw out 6 full rotations also does nothing. No effect at all. (tested both screws in the 636S flange, as the 539's has to much play in the shaft to be usable)
3) The rebuild kit, & both carbs did not have spring-loaded needles, but solid ones with a little wire clip to hold it against the float. Would that make a difference in the fuel pressure or flow?
4) Once I set the pump throw (in both carbs) at 17/64th's (.674687), it made the adjustable pin for the metering rod sit too high. Meaning at the pin's LOWEST setting, it's still sits higher than the 2.718 inch metering gauge said it should. About 3/64th's too high on my 636S carb, and 1/16th inch on the 539. This prompted me to tear the carbs down and reset/adjust them multiple times before giving up. In the end, both Carbs have needle pins with "elongated loops" on them, so I ignored the gauge and I eye-balled the adjustable screw to sit just below the top of the pin, when the pin was fully seated in the jet. tried Adjusting it a few more times, but nothing worked better.
So... Do you think pulling the rivets/full rebuild might work, or just cut my losses and buy a new carb?
- Tim
I have a Carter WO (636S-SA) carb on my CJ2a/L134. Engine is a fresh rebuild, & I paid (another) shop to make sure the mechanical timing was set. Starts and runs very well, but I had lots of backfiring upon acceleration and no power. I rebuilt the 636-SA using the basic $30.00 rebuild kit, after spending lots of time watching your videos from this site, and advice from the CJ2A web pages. Then I pulled it apart again, & then again, & again... I just could not get it to stop the backfiring or make any power. At the same time, I have a junk military 539-S carb I was pulling apart to practice and compare with my 636 (because I'm paranoid about losing parts & forgetting where they go...). So I then stripped all the new parts kit/bits out of the 636S and rebuilt the old 539. Still didn't fix the problem, so I pulled BOTH carbs apart into tiny pieces, & used the best bits from that big pile to rebuild one that is "mostly" a 539. This final rebuild fixed "most" of the backfiring & I can get the jeep into 3rd gear now. But even with the 539 carb, it still has no power, takes forever to accelerate and caps out at about 30mph on a flat road. When driving, it now will hesitate/stutter at about 1000-1200rpm (just before I feel the need to shift) but not when sitting still (in neutral I can rev it to almost 2000rpm).
Vacuum tests out at 22 pounds (idle) and 5 pounds (hard acceleration). I live at 5000ft elevation. Gauge has a slight flutter (+/- one psi) which I think is due to the engine builder not replacing the valve guides.
Fuel pump is a AC 577-C-066 putting out 6psi (with a 1/4 inch spacer). Fuel line has a pressure regulator on it, set at 3.5 pounds.
New (modern) distributor, coil, spark plugs and wires. Engine now has 3-4 hours of run time since its rebuild. Spark plugs look good. 12 volt conversion, but I've only got a single-wire alternator right now.
PCV valve is cleaned & tested good. Exhaust is old & rusty but clear of obstruction. compression is good in all 4 cylinders.
So here is the weird stuff I can't seem to fix or figure out:
1) No matter how I adjust the timing (rotating the dizzy) I can't get rid of the "putt-putt-putt" coming out of the exhaust. But the engine seems to run smooth at idle. Even at 200rpm(bottom choke valve just cracked & adjustment screw all the way out), it still idles smooth as glass.
2) Twisting the low speed idle screw (fuel-air mix) does absolutely nothing. Fully tight has no effect on the idle, compression or engine sound. Max lean should stall the engine, so how is that even possible? Also turning the screw out 6 full rotations also does nothing. No effect at all. (tested both screws in the 636S flange, as the 539's has to much play in the shaft to be usable)
3) The rebuild kit, & both carbs did not have spring-loaded needles, but solid ones with a little wire clip to hold it against the float. Would that make a difference in the fuel pressure or flow?
4) Once I set the pump throw (in both carbs) at 17/64th's (.674687), it made the adjustable pin for the metering rod sit too high. Meaning at the pin's LOWEST setting, it's still sits higher than the 2.718 inch metering gauge said it should. About 3/64th's too high on my 636S carb, and 1/16th inch on the 539. This prompted me to tear the carbs down and reset/adjust them multiple times before giving up. In the end, both Carbs have needle pins with "elongated loops" on them, so I ignored the gauge and I eye-balled the adjustable screw to sit just below the top of the pin, when the pin was fully seated in the jet. tried Adjusting it a few more times, but nothing worked better.
So... Do you think pulling the rivets/full rebuild might work, or just cut my losses and buy a new carb?
- Tim
Oilly