Carb Help

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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BSki
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Carb Help

Post by BSki » Sat Feb 10, 2018 4:44 pm

Hi everyone,

I think that I am having issues with my new carb. It now has just under 1500 miles on it and the jeep runs ok with the choke partially engaged.

I looked into the body of the carb at idle and can see fuel dripping past the venturi.

I also pulled the plugs and they are covered in black soot.

Not sure which carb it is, bought it from Ron it has only one spring loaded screw adjustment.

I have never torn apart a carb, nor have good knowledge on how they function.

Where should I start?

Thanks in advance

Brian


Marty, SoCal
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Re: Carb Help

Post by Marty, SoCal » Sat Feb 10, 2018 7:11 pm

Fuel coming out of the venturi with the choke partially closed is normal. If the choke needs to be set to make it run properly while warmed up then most likely there is either a vacuum leak at the base of the carb or the low speed jet is plugged with dirt inside the carb. There are plugs on the side of the carb that can be removed allowing you to remove the low speed jet and clean it out.

The needle/seat may not be seating properly if a lot of fuel is dripping out of the venturi at a normal idle speed, with the choke fully open. Try giving the carb a tap with a plastic screwdriver handle right where the fuel inlet goes into the carb. Tap the carb itself while the engine is running, not the fitting, many times this will unstick the needle and it will start running properly again.

If you find dirt in your new carb, it's not a warranty issue, you need to clean the fuel system and/or add a better fuel filter.
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Scoutpilot
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Re: Carb Help

Post by Scoutpilot » Sun Feb 11, 2018 3:27 am

BSki wrote:
Sat Feb 10, 2018 4:44 pm
Hi everyone,

I think that I am having issues with my new carb. It now has just under 1500 miles on it and the jeep runs ok with the choke partially engaged.
When did you have to start using partial choke to keep it running?
I looked into the body of the carb at idle and can see fuel dripping past the venturi.
Common with a flooding carburetor.
I also pulled the plugs and they are covered in black soot.
Common with a flooding carburetor.
Not sure which carb it is, bought it from Ron it has only one spring loaded screw adjustment.
This is important. Post a picture or two so we can see it.
I have never torn apart a carb, nor have good knowledge on how they function.
Don't do anything until we diagnose the issue
Where should I start?

Thanks in advance

Brian
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dinof
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Re: Carb Help

Post by dinof » Sun Feb 11, 2018 6:22 am

If you have a Carter Carburetor, I suggest you go to the "jeep draw" section and download & printout the info called "ordnance maintenance, Carter Carburetors" you are going to need it to help you along. Of course, that is if you have a Carter. Ron also lists a Solex. Let us know like Scoutpilot said about posting a picture.
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Wolfman
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Re: Carb Help

Post by Wolfman » Sun Feb 11, 2018 6:39 am

I will be #3.
Don't just take the carb. apart.
Could be something simple and you will do more harm than good.
Try to figure out what the problem is before you try to fix it !
Rule #1 Start simple.
Marty's vacuum leak idea is a valid one.
Start the engine. Get a can of spray carb. cleaner. The kind with the plastic tube would be better. You can pin point the spray instead of soaking the whole engine. Spray around the carb. base and the intake manifold where it mounts to the engine. These are the two most likely spots for a vacuum leak.
If there is a change in the way the engine is running, when you spray at a certain point, you have a leak there.
1500 miles since the carb. was installed. How many miles are on the engine ?? Could be the valves need adjusted. or time for a valve job. There is a test for that as well.
And there is always the possibility, there is a carb. problem.
Any way, start simple and go from there. Don't just tear it apart !!
Mike Wolford
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Chuck Lutz
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Re: Carb Help

Post by Chuck Lutz » Sun Feb 11, 2018 9:00 am

Is this a Joe's Motor Pool reproduction of an original Carter 539S carburetor?
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

BSki
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Re: Carb Help

Post by BSki » Sun Feb 11, 2018 12:08 pm

Thanks everyone,

I very much want to continue learning.....

I solved the dripping issue at idle with the choke off, it was as simple as backing off the throttle adjustment screw. So it was not allowing it to seat fully. Lesson one, I guess.

Now, at idle with choke off...it struggles upon initial acceleration and when playing with it in the garage dies sometimes when I pull the throttle slightly. Sounds like it is flooding?

I sprayed around the base of the carb and did not see or hear anything.

I would like to understand why the spark plugs were so black.

Then engine is newly rebuilt, same time as the new carb. I do not know how to post pictures to the forums.

Brian

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Re: Carb Help

Post by pkozak1 » Mon Feb 12, 2018 6:03 am

Don't forget to check your PVC valve for a slight rattle. If there is no rattle it will stay open when screwed together binding the coil spring inside and create a vacuum leak as mine did after my first rebuild and had to idle with 1/2 choke. I ended up cutting one full coil and one half of a coil off of the inside spring of the PCV valve in order to get a "rattle". Vacuum leak solved and ran fine with no half choke. it is an often overlooked vacuum leak.

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Re: Carb Help

Post by Wolfman » Tue Feb 13, 2018 5:52 am

Engine rebuilt at the same time the new carb. was installed. That reduces the chance of the valve clearance being too tight.
Plugs were black because you were running with the choke on, to over come a possible lean mixture. Makes the mix too rich. Black plugs.
Good point on the PCV valve. That could well be the smoking gun.
If the plugs are black now, they are fouled and could be miss firing. Going to need to replace the plugs before continuing. You may find the problem and not realize it, because the plugs are still fouled.
No doubt the idle screw adjustment was the cause for the main nozzle, in the venture, spilling fuel. Idle speed screw turned in too far will cause this, as you found out.
Now that the idle screw is set back where it should be and after you replace the plugs, readjust the idle mixture screw. The one on the base of the carb. with the spring on it. Initial setting. Screw the screw in until it is " lightly " seated. Then back it out 1 1/2 turns. This will give you a starting point. Then adjust the screw in or out as needed to get a smooth idle. After the engine is warm.
If this does work and you are happy with the PCV valve, we are still looking.
Did you try spraying carb. cleaner around the intake manifold gasket, where the intake manifold fits up to the engine block ??
Quick check on the PCV valve. Remove the line from the valve and block the inlet. See if this makes the engine idle better. If it does, you found a problem.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

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Chuck Lutz
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Re: Carb Help

Post by Chuck Lutz » Tue Feb 13, 2018 8:29 am

"New carb" = is this a Joe's Motor Pool reproduction? ...or is it a rebuilt? Who rebuilt it?
"1500 miles" = so this jeep with this engine and this carb performed perfectly; acceleration OK, Idle at 600RPMS, no bog down when flooring it for 1500 miles?

Sounds like a "New" problem, so with that in mind, is there an in-line aftermarket filter just before the fuel pump?
Have you looked into the gas tank when it is drained down to nothing to check for rust/debris?
Have you blown out the fuel lines?
Do you have a firewall mounted fuel strainer?
Did you clean out the gas tank? Is the tank new, the fuel lines new, the pump new?

No offense meant...but this is another "my jeep won't run" thread where responders have to dig out answers to the most common problems associated with what you are experiencing....fouled plugs, running with the choke OUT, running like crap....

It is always best to give more details in the first post to make it possible for responders to eliminate 3/4 of the possible causes based on INFORMATION they then have to wheedle out of the thread to sort out the possible causes.

WHO rebuilt the engine...WHO rebuilt the carb or is it an "NOS" or a Joe's carb? Did it in fact run perfectly for 1500 miles and what happened in the time period it began to act up?

Lacking suffecient information, I'll put two dollars on crud in the carb and back that up with two more on a tank with crap in it sending it through.
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

dinof
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Re: Carb Help

Post by dinof » Tue Feb 13, 2018 12:15 pm

Maybe it's time for the op to tell us some basic facts. Ok, here goes: Is it a Solex, rebuilt Carter, or a joes motor pool Carter?
Dino Falabrino
On the "G" since 1998.
1943 GPW 102310 DOD 3-3-43
1928 Model A Roadster Pickup
1930 Model A Tudor
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Re: Carb Help

Post by Wolfman » Wed Feb 14, 2018 6:58 am

Hey guys. :roll:
Way back in the first post, Brian said the carb. came from Ron and it only has one spring loaded adjusting screw at the base.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB


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