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CJ2A Stalling After Warm

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cj2a1946jeep View Drop Down
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    Posted: 19 July 2021 at 9:59pm
I am just getting started with our CJ2A restore.  First step is getting it running well.  I can get it started and it runs for about 10-15 minutes.  I can see the temp gage go up near 180 degrees (it was about 90 degrees outside today) and it just quits running.  After that it's near impossible to restart until the temp comes down.  I checked for spark after it quit and it appears I still have spark so I somewhat ruled out the coil and condenser.   I feel like it's carb or fuel related.  

It's an old tank with a newer fuel pump.  It's possible that when it reaches 180 degrees it's too hot of an operating temp. Anything below that it idols and drives pretty well.

The carb looks old and could use some work, but it's strange to me that it runs almost perfect until it hits that magic operating temp. 

Anyone have any ideas.  I am somewhat new to all this and trying to teach my 16 year old about these old Jeeps.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WeeWilly Quote  Post ReplyReply Direct Link To This Post Posted: 19 July 2021 at 10:13pm
 when it stops running try to spray a little gas in the carburetor. If it starts up you will know it is fuel related.

   Jim 
47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 20 July 2021 at 12:39am
If it has bright blue spark after it quits, the ignition system is probably good. Anything less is suspect.

Thus, it is fuel related. The first check is what Jim suggested above. If fuel sprayed down the carburetor gets it going, take the fuel cap off while listening for a sucking sound. I suspect that your vented fuel cap is no longer vented. If you hear a sucking sound, try to start & run the engine with the fuel tank cap off. If it solves your problem, you have found the issue. A plugged vent can be unplugged it does take a while & a bit of soaking in a solvent.

Please keep us in the loop. Thanks, Cpt Logger.

PS. Welcome aboard!


Edited by cpt logger - 20 July 2021 at 12:42am
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cj2a1946jeep View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cj2a1946jeep Quote  Post ReplyReply Direct Link To This Post Posted: 20 July 2021 at 9:21am
Thanks for the tips. When I spray gas on the carb it wants to start but sputters out after the newly added fuel is burnt up.  I am pretty sure I have good spark.

I did not try to run or start with the fuel cap off yet. I will do that tonight.  What I am finding is if I get the Jeep to start after the stall and after it cools down a bit, I need to run full choke with an almost full throttle as it somewhat surges. After a few minutes of this, if I can keep it running, it will work itself out and idle smooth till the process starts over when it reaches temp. 

Also picking up a new fuel filter. I am not well versed in carb work but it seems to me if it were the carb it would happen all the time not just when warm. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 20 July 2021 at 11:15am
If it will idle at all the idle circuit in the carburetor is clear which is a good sign.

Lots of things can cause this and most are fuel related. The gas cap, as already mentioned, is easy to check. If it is not a vented cap, or if the vent is plugged it will run a while then starve out the pump. After sitting a bit gravity primes the pump again and it will start. Just loosen the cap and see if that changes anything.

A sticking float valve in the carburetor can also cause it to run a while then starve out at the carb.

Engine temp may not have anything to do with it, but heat can cause vapor lock, but that is not likely at 180 degrees unless the fuel line is against the exhaust manifold. 

One of the first things I do when bringing an old car back to running condition is rebuild the carburetor, they almost always need it, especially when they have sat a long time. It is a pretty simple carburetor, but getting it thoroughly clean can be a challenge. There are good Youtube videos out there on rebuilding them, and if you decide to do it buy a quality master kit which has every thing in it, and modern material that resists the ethanol fuels. The cheap kits aren't worth the postage.

If you don't feel comfortable rebuilding the carburetor send it to "Scout Pilot".
If you can't get there in a Jeep you don't need to be there
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OnlyOneDR Quote  Post ReplyReply Direct Link To This Post Posted: 20 July 2021 at 4:44pm
Check and make sure the heat riser is closing, otherwise it is just boiling out the carburetor.  It is probably stuck open.

Edited by OnlyOneDR - 21 July 2021 at 7:21am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cj2a1946jeep Quote  Post ReplyReply Direct Link To This Post Posted: 20 July 2021 at 9:55pm
I think it’s the heat riser. It’s stuck in the cold or resting position. Any ideas how to get in “unstuck”?  Thinking I need to remove both manifolds which means broken studs....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cj2a1946jeep Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2021 at 10:49pm
Thanks again everyone. It was the heat riser. We finished replacing today and she runs pretty good and more importantly it keep running and is no longer boiling the fuel.  We also ended up seeing two cracks in the old manifold anyway. 

Sometimes you fix one issue and find another. We now have some gas leaking from the carb after it’s warm and has been running for a while. It’s probably due for carb work anyway. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OnlyOneDR Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug. 2021 at 6:45am
Glad we could help!
Searching for time to put it all together...
1950 CJ-3A #37751 In Pieces
1969 Chevy Blazer Resto-Mod Waiting for its day...
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