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Dark Horse View Drop Down
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    Posted: 17 Nov. 2014 at 10:16pm
Over the past year or so I've been plugging along getting this '46 CJ2A running again. After rebuilding the WO carb and putting in new points and condenser, setting the timing, etc., it was running very well, but was overheating (would get up to at least 200F or more within 20-30 min at fast idle. I put the project on hold for a while until I could take the radiator down to the shop and have it checked out, during which time I also replaced the water pump because I could see some weeping from the hole. So, re-installed the radiator and it seems to run fairly normal on temp (not completely sure yet, since the weather has cooled quite a bit).

BUT, now it runs smoothly until it gets up near T-stat opening temp, then it begins to run rough (guessing somewhere around 160-180F). As long as it is around 140-150F or below it runs like a dream. Above that, it idles rough and wants the throttle advanced a little to keep the rpm from falling too low. At higher rpm it is less obvious, but you can tell it isn't quite "smooth".

So, my two thoughts were: 1)Ign. Coil beginning to go bad, showing up under heat? My coil is mounted behind the dash, but offhand I can't remember whether it is the keyed coil (which the Jeep originally came with) or a regular coil someone just mounted back there (I kind of think it's the latter). Or, possibly: 2) Idle mixture is too rich? What's odd about that would be that it wasn't doing this before when it was running a lot hotter than it is now. In fact, the problem never showed up until the first time I ran it with the new water pump and freshly serviced radiator, where it ran cooler than it was before (and has ever since). 

The Jeep is currently 30 miles away, and I only get to visit it on weekends when I'm at the farm, otherwise I'd just investigate all this stuff one at a time myself. As it is, I'm trying to think through all the things to check at once, so when I go there next, I'll have a more inclusive list to check. Any ideas?

Thanks


Edited by Dark Horse - 17 Nov. 2014 at 10:18pm
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scoutpilot View Drop Down
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Points: 4373 		Post Options Post Options   Thanks (0) Thanks(0)   Quote scoutpilot Quote  Post ReplyReply Direct Link To This Post Posted: 17 Nov. 2014 at 11:18pm
Does the temperature advance smoothly through the opening of the T-stat, then drop down? What RPM is normal idle for you? Any idea how much oversize the cylinders are?  Bored .050 over and above can produce more heat than normal.

Possible  issues:
Air bubble in head
Running at high idle will cause a large temperature rise.
Mixture could be too lean.
Timing could be advanced too far.
Could be a failing coil.
Could be a combination of any of the above.
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52 M38 View Drop Down
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Are any of the cylinders "clean" when you look through the spark plug hole?  Once everything heats up and expands you might have a head gasket leak.  It will be very noticeable, at least mine was.  #4 was sparkly clean. 
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Points: 49 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Dark Horse Quote  Post ReplyReply Direct Link To This Post Posted: 17 Nov. 2014 at 11:50pm
Scout - yes, the gauge behaves as you would expect in response to the T-stat. I don't know the actual RPM of the idle, but probably 700 or so. Don't know anything about the bore. But the issue now doesn't seem to be OVER-heating anymore. I "think" that is solved with the radiator. The problem NOW is rough running when it gets up to NORMAL operating temp, but it runs fine below about 150 or 160. The overheating issue was only mentioned to say that it wasn't running rough before even when it WAS overheating, but now it runs rough when it gets up to normal operating temp, but runs smooth until then. I'm interested in hearing any experience you (or anyone) has with symptoms of a failing coil.

M38 - I haven't pulled any plugs since this problem just popped up. I replaced all the plugs last year (haven't done anything but test run it a 12-15 times since, no driving), and cylinders looked normal at that time (but there wasn't this problem then either).
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Points: 4373 		Post Options Post Options   Thanks (0) Thanks(0)   Quote scoutpilot Quote  Post ReplyReply Direct Link To This Post Posted: 18 Nov. 2014 at 12:53am
That leaves only one thing to my mind. Slow flooding. 
Possible causes:
Fuel pressure in excess of 4.5 - 5.0 PSIg
Needle and seat dirty, blocked (need a good filter to stop detritus from entering the carb. Preferably one between the tank and pump and one between the pump and carb, or 
Needle is cocked to one side. (This is caused by a gouge or wear spot in the tang of the float that contacts it or an excessive angle on the tang.) 
Float set too low (3/8", +/-0")
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Points: 49 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Dark Horse Quote  Post ReplyReply Direct Link To This Post Posted: 18 Nov. 2014 at 2:58am
Thanks for the reply. I can appreciate the logic in your response, but I don't think it's slow flooding. The reason is that as long as the temp doesn't get above 150-160 the problem doesn't appear, no matter how long the engine runs. With the recent colder temps, I had been test running the engine a few times (draining/changing coolant, etc.) and couldn't get the temp much above 140 even after static running at about 1/4 -1/3 throttle for half an hour. The problem never showed up. But during the late summer when it was still warm, I could get it up to operating temp in about 10 minutes at that throttle setting, and the problem would appear. Yesterday, I took it out for a drive around the property and was able to get the temp up in the 160-180 range, and the problem re-appeared. It definitely seems to be temp related, rather than time related, but not due to actual overheating - it just has to get to normal operating temp to start acting up. I've heard of bad coils running OK until they get hot, but I don't know what the symptoms associated with that are. Most bad coils I've been around won't start the engine.
 Thanks
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plowpusher View Drop Down
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check the heat riser flap in the exhaust manifold it could be stuck in the closed or nearly closed position
when i grow up i wanna be a kid
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Points: 49 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Dark Horse Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov. 2014 at 3:57am
Originally posted by plowpusher plowpusher wrote:

check the heat riser flap in the exhaust manifold it could be stuck in the closed or nearly closed position

Hadn't thought of that, because it was working fine fairly recently, but I haven't thought to recheck it since this problem popped up. I think it's still working OK, but I will definitely take another look. It would seem to me that if it were stuck, it could very well cause the type of thing I'm seeing, so that's a good idea to check.

Thanks!
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I found an NOS bellow type thermostat, the comparison it to a modern thermostat is unreal. The size of water passage is much larger, and the whole thing sits lower in the housing so it opens sooner.
I have seen posts here about drilling a 1/8' hole in modern thermostat to allow air past, and some water so that it can do the following.
Purge all air from cooling system , and open the thermostat sooner, circulate enough water to cool engine.
Also unless you have heater(s) you should have a bypass hose to circulate water from block back to lower radiator hose.
 
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UPDATE: I had a chance to work this problem a little this afternoon. My plan was to start by rechecking the timing, make sure it is right, then run the engine until the temp was up and the rough running started, then play with the idle mixture to see if it made a difference.

So, I started by re-setting the points gap (it was just a few thousandths over .020), then went to set the timing. What I found was that the distributor could be rotated quite a bit either way before I ever loosened the distributor clamp. A little investigation revealed that the distributor hold-down clamp bolt was loose (the one that holds the distributor down into the block, not the one that is normally loosened to adjust the timing). I tightened this bolt down and it stopped the unwanted rotation of the distributor. I loosened the other clamp and set the timing as usual, then fired the Jeep up and drove it around the pastures for 30 min. I never was able to get the engine temp over about 160F (ambient temp was in the high-50s this afternoon). The rough-running never occurred, either. I finally gave up because I couldn't get the temp any higher, and I couldn't get the engine to run rough. I have to wonder now if the rough running wasn't caused by wandering timing, and the higher temp (180 or so) was a RESULT of that, and not the CAUSE of the rough running.

Just as I was about to shut it down for the night, lo and behold, the idle dropped down too low for it to idle reliably, and I had to blip the accelerator pedal a few times to get the idle to pick up again. I opened the hood to check the idle stop screw and found it is screwed in as far as it will go, yet it isn't idled up really high. I'm not sure what the deal here is, but it seems to be more of a mechanical linkage issue more than a carburetion problem. I will have to look into this some more. In any case, the engine wasn't running rough this time, it was just trying to drop below a reliable idle. As long as I manipulated the accelerator linkage to prevent that from happening, it continued to run smoothly. I guess it's another problem for another day...


Edited by Dark Horse - 21 Nov. 2014 at 3:43am
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Approximations of settings are hardly ever good enough. Now that the distributor problem has been discovered and dealt with, when you are ready to return to it, take your vacuum gauge and dwell/tach with you. You'll need to adjust the carb before you get mad at it. Throughout the following procedure, do not worry if the motor quits while adjustments are being made. Merely back off the adjustment a bit from what you did. Restart and continue. 
 1. Watching the vacuum gauge, rotate the distributor (points at .020", +/-0") until you've achieved the highest vacuum reading you can get.
 2. Watching the dwell/tach, turn the distributor to lower the RPM by 100. Lock it down.
 3. Next, turn the steel Idle Stop Screw slowly counter-clockwise while observing the vacuum gauge. Again, you're going for the best vacuum reading you can get.
 4. Now you can adjust the idle using the brass Idle Mixture Screw. You're looking for 600-700 idle RPM. Remember, IN is rich, OUT is lean.

Good luck.
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Points: 49 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Dark Horse Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov. 2014 at 2:23pm
Thanks for the advice, Scout. There's a lot of good info there. I'll have some more questions for you before I get a chance to give it a try, but I'll mull it over a bit to try and think of everything I need to ask first.
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I'm almost always here. Take your time.
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First question (off topic): Your username suggests that perhaps you own a Bellanca or American Champion 8GCBC?
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I wish I did. I've spent enough on Jeeps to pay for one of those fine airplanes. I flew OH-6s (LOH) with the Scout Platoon, 'C' Troop, 16th Air Cav, 1st AVN BDE, out of Can Tho, RVN back in the early seventies.
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Originally posted by scoutpilot scoutpilot wrote:

I wish I did. I've spent enough on Jeeps to pay for one of those fine airplanes. I flew OH-6s (LOH) with the Scout Platoon, 'C' Troop, 16th Air Cav, 1st AVN BDE, out of Can Tho, RVN back in the early seventies.

That's even more awesome! The Loach is like a little sports car, and I always thought it would be a hoot to fly. While I'm no rotor-wing guy, I have a dear friend that spent an entire career at Rucker training you guys, and I have learned an enormous amount from him. Thank you for your service, and you have my deep respect as an aviator.

My mount is a '47 Cessna 120 that I've owned and maintained for the past 16 years. It is only surpassed in age around here by my old rust bucket '46 CJ2A.
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Send me a pic of it, please.
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Points: 49 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Dark Horse Quote  Post ReplyReply Direct Link To This Post Posted: 23 Nov. 2014 at 5:31am
Man, that Loach is a sexy beast.

This was about 8 or 10 years ago. The airplane hasn't aged at all since then. I, on the other hand...



Edited by Dark Horse - 23 Nov. 2014 at 5:33am
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