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Help tuning a 2gc |
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NCtoy 
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Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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 Topic: Help tuning a 2gcPosted: 22 Mar. 2020 at 10:20pm |
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With all the carburetor talk around here I decided give another shot at tuning mine. Overall it runs great, but there is a dead spot right off idle. If you open then throttle slowly it will rev up smoothly. If you quickly floor it, it will take off after a slight sputter Where it really gets me is if you’re idling along and quickly give partial throttle, like when you need a blip of throttle to bump over a log or bank or something, it will stall out.
It makes me think it’s an accelerator pump issue, but it seems to be squirting fuel fine. I replaced it once last summer, but no real help. There is a little wear in the linkage, giving it some slack. I’m not sure if that’s affecting it or not. I’ve double checked the basics, no vacuum leaks, timing is at 4 degrees. I have it tuned a little rich at idle, as it seems to let it run cooler in hot weather. Where should I check next?
Edited by NCtoy - 22 Mar. 2020 at 10:22pm |
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JeepFever
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Posted: 22 Mar. 2020 at 10:40pm |
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The accelerator pump "piston" has to run in the proper range in the bore. I forget the exact procedure/dimensions etc., but I remember it involved bending the link that goes from throttle arm to pump arm.
If you can't find any info, let me know, and I will see if I can remember where I found it. This was many years ago, but the problem was similar to what you describe. After this adjustment it had zero dead spots. edit. just re-read your post . . slack in linkage, I bet that is the issue.
 Edited by JeepFever - 22 Mar. 2020 at 10:43pm |
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Bruce W
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Posted: 22 Mar. 2020 at 11:07pm |
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Power piston is sticking in its bore. Manifold vacuum pulls the power piston down against a spring in its bore which pulls the metering rod down into the main jet. When you accelerate, manifold vacuum drops and the spring pushes the piston up which raises the rod. The piston gets dirty with carbon and other crap and gets sticky, and usually sticks in the down position. BW
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It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
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NCtoy
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Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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Posted: 25 Mar. 2020 at 12:38am |
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Got some time to mess with it tonight. I checked the power valve rod and it was moving freely. Then I reset the float. I had it a little low originally, and thought maybe there wasn’t enough fuel in the bowl to fill up the accelerator pump well all the way.
Finally I put it back together and re-bent the accelerator pump rod to take out the slack. A test run of the engine seemed to show some improvement, but still stumbling. So I straightened it out a little more. Now it responds great just off idle and throttle response is much better, but after a test drive I’m still having trouble. The dead spot is gone and everything is better overall, but it’s still bogging down if you hammer on it from idle.
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JeepFever
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Posted: 25 Mar. 2020 at 4:07am |
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Good to hear!
Can't say I have ever tried that.  Seriously though, what does the mean? lugging along at idle, and then pedal to the metal? That seems an extreme situation, a little clutch to let it rev first might be better under those circumstances. I suspect you must mean something else.
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Gil
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Joined: 29 July 2016 Location: N.B.Canada. Status: Offline Points: 975 |
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Posted: 25 Mar. 2020 at 11:19am |
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Make a search on the web for cj2a adjust carburetor.My Jeep was doing about the same thing your Jeep is doing and mind was the adjustment with the pump stroke it have to be adjusted to 17/64.Try that it’s not a big adjustment to check.
Giles
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1946 cj2a 59108
1998 Jeep Cherokee 2 doors 2016 Jeep Cherokee TrailHawk |
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Bruce W
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Posted: 25 Mar. 2020 at 5:53pm |
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“ it’s still bogging down if you hammer on it from idle.”
Kind of like a 4-barrel with secondaries that won’t open? BW
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It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
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NCtoy
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Posted: 26 Mar. 2020 at 1:20am |
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Yeah, I keep wondering when my 4 barrel will kick in. About the same time as my other 2 cylinders I expect.
What I mean is if you are driving at low rpm and quickly floor it, instead of accelerating away, it’s stumbling and not going anywhere. Yes, it is a little rough on it and I don’t normally drive that way, but when you mash the gas it should start to pull, not choke down. My cj 5 with the dauntless doesn’t have this problem. I should add, as long as you ease into the throttle, it will take off fine.
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WeeWilly
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Posted: 26 Mar. 2020 at 1:56am |
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It might be the timing is off a little or the vacuum advance isn't working right. Jim
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47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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NCtoy
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Posted: 27 Mar. 2020 at 6:41pm |
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You might be onto something with that. I had checked the timing and that it was advancing, but not the vacuum advance specifically. Mines doing nothing and won’t hold any vacuum. Trying to find another, but I’m not sure that will make a huge amount of difference. It can’t hurt though.
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Bruce W
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Posted: 28 Mar. 2020 at 12:37am |
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Yep, it will. I used to fight that all the time, I guess I forgot about it. Sometimes, if the parts dept. didn't have the correct one (there are lots of different applications for the same engine, depending on other equipment) I would put on whatever they had - a working wrong vac. adv. is better than a non-working right one. BW
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It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
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NCtoy
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Posted: 30 Mar. 2020 at 2:36am |
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Got the vacuum advance put on today and double checked to make sure everything is working. A test drive showed more improvement. I’m pretty happy with how it’s running now. Much better throttle response and low end than it has had in years. Thanks for the help!
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JeepFever
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Posted: 30 Mar. 2020 at 3:24am |
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Great to hear! I got a chance to drive Wilson today. I tried in several situations to "punch it". Not normally how I drive, but I could not get it to "hesitate" or sputter in any way. If I applied sudden full throttle at low rpm, it would not necessarily pull hard, until rpms picked up, but it did not complain as much as I thought it would.  This does have me wondering though if there are some improvements to be gained with some tuning. I might need to check initial advance, and whether the vacuum advance and centrifugal weights etc are working correctly. I rarely wish it had more power, but maybe could be saving some fuel also? |
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WeeWilly
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Posted: 30 Mar. 2020 at 3:55am |
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Great!!! Don't be afraid to play with the timing a little to squeeze a little more performance out of it. I bought a new Plymouth Scamp in 1973 that seemed sluggish and I adjusted the timing by ear and it made a big improvement. When I took it in for 1000 mile check up the mechanic asked me if I had adjusted the timing. I affirmed I did and he ask me what kind of fuel mileage I was getting. When I told him he said he was going to leave the timing just the way I had it. Why it didn't run good at manufacture specs is beyond me. Jim
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47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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NCtoy
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Posted: 30 Mar. 2020 at 6:23pm |
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I’ve got the timing set at 5 degrees. It seems to start the easiest with it set there. I may play with it a little and see if I can get a little more out of it.
Jeepfever did you try it in 1 or second? Or in your case 2 or 3rd, i think you have a 4 speed swapped in right? Mine will do fine in third and just start pulling, but in the lower gears is where I get the hesitation. Although it’s better now than I can remember, punching it from just off idle will still make it hesitate. But rolling on the throttle smoothly and it takes right off.
Edited by NCtoy - 30 Mar. 2020 at 6:32pm |
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NCtoy wrote: