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CJ2A Stumbling and Possible Solex Issues

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cyates176FA View Drop Down
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    Posted: 06 June 2022 at 11:10am
I've got a 47 CJ2A with a new fuel tank, new fuel pump, and new Solex carb (installed by PO). I've been searching the forum the last day or two but can't find any threads that discuss my exact issues. 

A little background first. Sorry for the long post; but I wanted to put as much information out to help with potential solutions. 

Up until maybe 3 days ago, the Jeep ran fairly well (good idle, decent power, etc.). I use it for riding around town, so maybe 15-20 miles per trip. I went out the other day, and it suddenly started stumbling and jerking. I stopped to let it idle, and I could hear it stuttering - not backfiring, though. I made it back to the house, shut it off, came back maybe 10 minutes later and it cranked right up and ran fine like before. 

The next day, it started up fine; but maybe 2 or 3 miles in, it started the same stumbling but this time the engine died. I let it sit for a few minutes and then it took about 3-5 minutes of cranking to get it running. 

Yesterday I took it out just in the neighborhood to see if I could troubleshoot whether or not the choke/ throttle would make it better or worse when running. At that point, it died and wouldn't start. Got it back home and started troubleshooting.

What I've done so far: 

I pulled, cleaned, and re-gapped the plugs (#2 was well under the gap). Pull the distributor cover, checked the points, and made sure I had power getting to the plugs. Brought it up to TDC on #1 to try to get the timing to a point where it should at least start. No luck, other than maybe 45 seconds of a very rough idle. During that time, I put my hand over the carb and it immediately died. I did that to see if maybe I was pulling air from somewhere other than the air intake. 

I have the mechanical fuel pump with the glass bowl. The bowl is very full, so I imagine I have good fuel flow from the tank to the pump. I then manually moved the throttle, and didn't see much fuel going into the carb. It dribbled in a little; but didn't look like it was flowing at any regular rate. Pressure regulator (the dial type from the parts store) is set at approx. 2 psi.

My questions: 

1. How much fuel should be coming out when I manually manipulate the throttle with the engine off? Seems like it would a spray as opposed to a drip. I'm wondering if I've got something blocking the line. I should have known better; but there isn't a filter between the pump and the carb (mea culpa). 

2. Is the pressure regulator necessary for the Solex? I'm currently having the original Carter WO rebuilt, so I'm not wanting to put too much into the Solex setup. If it could be deleted at least for troubleshooting, it may make it easier to find my issue.

3. My distributor retainer was loose (I could move it fairly easily by hand), and the distributor cap seemed a bit loose (could twist it a few degrees either way without the distributor itself turning). To me it seems unlikely as the issue was sporadic at first; but could it have jumped a tooth or something? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch 1960 Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2022 at 9:52pm
Fuel boiling/vapor lock?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2022 at 10:11pm
Yes, a pressure regulator is usually recommended with the Solex. These carburetors cannot handle as much pressure as a Carter WO or YF and with too much pressure the float valve can be overridden and that will cause the symptoms you described. 

I suspect when you tried the choke that caused even more fuel dump which flooded the engine. If I am correct that is why it would not start afterwards. 

The distributor needs to be tightened, and if the cap will move with the clamps on it is either not seated properly or a poorly made cap, but since it will start and run okay before you get to the stumble I seriously doubt this is an ignition problem.

What part of East Tennessee are you in ? If close enough I may be able to help you if you don't figure it out yourself. 


Edited by Oldpappy - 06 June 2022 at 10:16pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyates176FA Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2022 at 10:42pm
Originally posted by Dutch 1960 Dutch 1960 wrote:

Fuel boiling/vapor lock?

Could it be that if the stumbling starting (in some cases) as soon as it starts? Seems like something that would come about once the engine is hot. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyates176FA Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2022 at 10:55pm
Originally posted by Oldpappy Oldpappy wrote:

Yes, a pressure regulator is usually recommended with the Solex. These carburetors cannot handle as much pressure as a Carter WO or YF and with too much pressure the float valve can be overridden and that will cause the symptoms you described. 

I suspect when you tried the choke that caused even more fuel dump which flooded the engine. If I am correct that is why it would not start afterwards. 

The distributor needs to be tightened, and if the cap will move with the clamps on it is either not seated properly or a poorly made cap, but since it will start and run okay before you get to the stumble I seriously doubt this is an ignition problem.

What part of East Tennessee are you in ? If close enough I may be able to help you if you don't figure it out yourself. 

I don’t know that the regulator has been set higher than the 1.5-2 psi. range. But when I took the plugs out to check the gap they were pretty dark, though that mostly wiped off with a rag. My plan is to start at the carb side of the fuel pump and check for any blockages. The fact that I don’t see any fuel going into the carb when I move the throttle makes me think it could be blocked. I’ll detach the line and see if fuel comes out of the pump when I crank the engine. From there I’ll try to clean out the regulator. After that it’s just the carb that could be blocked and not letting fuel flow. 

Putting the choke on is the only way to keep it lit, and then it runs very rough. I’m hopeful that it’s just something in the line blocking the fuel from flowing. 

Am I right in thinking that I should see fuel spraying in the carb when I move the throttle with the engine off? The fuel pump is full; so I figured there’d be enough pressure that I would see a spray of fuel looking down the carb. 

I live in the Knoxville area, if that’s close by to you. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2022 at 9:40am
I am about an hour and a half from Knoxville, so not too far. 

This post clarifies some things I wasn't sure of in the first. I thought you meant that when you pulled the choke it died, but if it is the only way to keep it running you either have an air leak or a possible blockage which would most likely be in the float valve or one of the circuits in the carburetor. 

If the accelerator pump is working you should see a little spray when you pump the throttle.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyates176FA Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2022 at 9:52am
Originally posted by Oldpappy Oldpappy wrote:

I am about an hour and a half from Knoxville, so not too far. 

This post clarifies some things I wasn't sure of in the first. I thought you meant that when you pulled the choke it died, but if it is the only way to keep it running you either have an air leak or a possible blockage which would most likely be in the float valve or one of the circuits in the carburetor. 

If the accelerator pump is working you should see a little spray when you pump the throttle.

Yes, once it got as bad as it did the other day, you've got to manipulate the choke and feather the throttle to keep it running. I did get it running enough to put my hand over the barrel. It had a lot of vacuum and died immediate when I blocked it off. 

The pump in the carb just drips maybe 3-5 drops, so I'm definitely getting the impression there's a blockage. 

I'll be running through the steps I mentioned above after work today, and I'll report back what I find. I'm hoping there's a blockage somewhere in the line or the pressure regulator. I'm having the original WO carb rebuilt; but I'd prefer to have the solex working correctly as well. 

Now that I think of it, I may swap the regulator with the one on my CJ5 that I know functions properly - seems an easy enough way to rule out an issue with the regulator. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WKWillys Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2022 at 9:06pm
Just a thought, but is your gas cap vent clear?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyates176FA Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2022 at 9:32pm
Originally posted by WKWillys WKWillys wrote:

Just a thought, but is your gas cap vent clear?

In all honesty, I probably need a new gas cap anyway. Mine is a bit chewed up and doesn’t make a great seal. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyates176FA Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2022 at 9:39pm
Originally posted by Oldpappy Oldpappy wrote:

I am about an hour and a half from Knoxville, so not too far. 

This post clarifies some things I wasn't sure of in the first. I thought you meant that when you pulled the choke it died, but if it is the only way to keep it running you either have an air leak or a possible blockage which would most likely be in the float valve or one of the circuits in the carburetor. 

If the accelerator pump is working you should see a little spray when you pump the throttle.

Tested some stuff tonight and here’s what I found. 

The pump pushed fuel while cranking. Replaced the hoses from the metal line to the carb and installed one of those clear filters between the pressure regulator and the carb. The filter filled up about half way while cranking. The Jeep still didn’t start though. I had the choke out and was feathering the gas pedal and could hear it wanting to fire. 

I did, however, notice fuel on the block beneath the fuel pump. The metal line that comes out of the carb side of the pump seems loose. It’ll require disconnecting the line to tighten the fitting, so I’ll try that tomorrow. Wondering if that loose fitting could be cutting the pressure and causing the weak flow at the carb. 

I’ll look at it again tomorrow after work, and see if tightening that fitting helps. 

Let me know if any of this keys you up with any possible causes. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2022 at 11:30pm
Hoses ? These are always a potential source for air leaks. I avoid any rubber hoses in my system other than the flex line with flare fittings from the hard line on the frame to the pump. If you have hoses from metal line to the carb they should at least have two clamps on them to prevent air leaks.

"Wondering if that loose fitting could be cutting the pressure and causing the weak flow at the carb." 

That is certainly a problem, if fuel is leaking out, air is leaking in, and fuel leaks are never not a problem.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyates176FA Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2022 at 11:40pm
Originally posted by Oldpappy Oldpappy wrote:

Hoses ? These are always a potential source for air leaks. I avoid any rubber hoses in my system other than the flex line with flare fittings from the hard line on the frame to the pump. If you have hoses from metal line to the carb they should at least have two clamps on them to prevent air leaks.

"Wondering if that loose fitting could be cutting the pressure and causing the weak flow at the carb." 

That is certainly a problem, if fuel is leaking out, air is leaking in, and fuel leaks are never not a problem.   

Planning to let it dry out tonight just in case some of the fuel I noticed was from the other work I did tonight. I’ll get someone to crank the motor while I check for the source of any leaks. 

I prefer the metal fuel lines as well, and once I get the WO back, I can see about getting something more rigid in place. 

But for now, I’ll try to track down what appears to be a fuel leak near the pump, and see if that improves pressure and gets the engine running again. 

Carburetors are admittedly something I have limited experience with, so it’s sort of slow going.

I appreciate all the replies to help me sort this out! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2022 at 8:12am
You will be better off with the Carter W-O than the Solex. You will want to install a good filter between the pump and carburetor to protect your rebuilt carburetor. Just a tiny bit of debris getting into the carburetor can cause problems.

I like to use a Carter or AC glass bowl filter mounted at the carburetor inlet fitting. The AC filters with replaceable paper elements are easier to find than the Carter with the ceramic element. Either work well, but the ceramic is the best ever made and lasts forever because you simply clean the element with a solvent when it needs it. The glass bowl lets you see when it needs cleaning or replacing, also lets you see whether fuel is getting to the carb.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote OnlyOneDR Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2022 at 10:21am
Check the heat riser on the exhaust manifold.  These have a habit of getting stuck and cause a host of fuel/driveability issues when they do.  It sounds like yours is not working properly.

Do a search on the site and you will find a lot of posts related to it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyates176FA Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2022 at 10:43am
Originally posted by OnlyOneDR OnlyOneDR wrote:

Check the heat riser on the exhaust manifold.  These have a habit of getting stuck and cause a host of fuel/driveability issues when they do.  It sounds like yours is not working properly.

Do a search on the site and you will find a lot of posts related to it.

I will check that out! 

Given past Jeep experience, I'm guessing there are a few different issues at play here. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeeper50 Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2022 at 6:59pm
I ran a Solex on my Fhead 134 in my CJ3B, and was having the same issues, I installed a M38 fuel pump spacer on my Fhead it lowers the fuel volume pumped by lessening the fuel pump lever travel. The Solex liked the change. my engine liked the change, I liked the outcome, all parties were happy. End of story.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2022 at 8:24pm
Now we know what those spacers are for!
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X 2 on that old pappy!!
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