Carter YF overflowing

I have a Carter YF 4002s (Same as SD938 but bowl vent connects to air cleaner) in my '69 CJ5 with the F134. The problem is the carb started dripping fuel out the bottom. It was rebuilt last summer by a local carb shop and ran better than it ever until this happened. I'm guessing the float needle isn't closing, so I pulled it apart expecting it to be dirty or worn. It looks perfect.

All the adjustments look good and the float isn't gas logged. Is it possible the fuel pump is overpowering the needle/seat forcing it open? I have the single throw pump (no sight glass on top) that's supposed to not pump when there is pressure in the gas line to the carb.

Any thoughts?

And WHERE is the fuel filter?

Thanks!

 

When is it dripping fuel?
All the time? Or just when it's hot?

 

It drips all the time when it's running.

 

Fuel pump pressure is critical to these carbs. Should be 2-1/2 to 3 psi. An inline regulator used to be a popular upgrade.

Also in Jeep applications the float valve orifice is smaller than the one provided in many rebuild kits, and the needle is spring loaded. Float height specification differs too, depending on the valve assembly.

These 'rough terrain' mods help the float not be "overpowered," as you rightly guess.

Quite possibly your carb rebuilder was not educated on Jeep variants.

 

Fuel filter is a screen in the tank, on the inlet end of the fuel line (IIRC), and in the glass bowl pumps there was also a fine screen. Personally I like to add a filter in-line before the pump.

 

DO NOT RUN YOUR MOTOR AGAIN UNTIL YOU ADJUST YOUR FLOAT! THIS IS A SEVERE FIRE HAZARD. Your float is too high. It should be at 5/16" without the gasket in place. This setting is based on the solid brass needle. Which needle and seat do you have installed?

 

I had same problem. Engine running rich. If you pull the air horn off the top there may be excess fuel running inside. Cured with in line fuel filter, in line fuel pressure regulator, and finally the correct float setting. Ended the problem.

 

It's dripping out of the bottom of the bowl where the "pump lifter link" sticks out. I had to look up the name of that thing! Lol! Why did it take a year to start leaking?

Okay, so I'll check the float adjustment and gas cap. Definitely going to add a fuel line filter, too.

 

Thanks, guys!
Scout, I have the needle/seat with the rubber tip. Does that make a difference in the float adjustment? My FSM lists the float at 17/64" for the 4002s and 5/16" for the 938sd.

 

I went thru the same thing this winter. Purchase the kit with the spring loaded brass needle and proper seat and don't look back. Not cheap at about $90, but it fixed the issue. While it is apart, check the throttle shaft for wear. I got by with just a shaft and no re-bushing of the body. Runs and starts like new now. The big Jeep suppliers sell the same thirty dollar kit as the auto stores, and even though they are supposed to work with our application, they do not. I learned all of this the hard way. Good luck.

 

BTW, does yours seem to leak more when it is sitting or running?

 

I think the float is set too high, needs new float needle, plis check the strange shaped seal around the accelerator pump lifter to make sure it is in place. Then the fuel filter and pressure regulator. Should fix it.

 

Yooper; it only leaks when its running.

 

Needle and seat. Scout pilot or the Carburetor Shop. I went thru two carb kits with the rubber tip, and went so far as to machine an orifice for the seat that was to Jeep specs, all of which can be found in another thread. The proper parts cured all of my problems. The larger surface area in the rubber tipped seat is the biggest culprit in my opinion. Yes, you can do regulators and all that jazz, but why not repair it the way it was designed to run from new. I've been on some rough roads and steep hills with the Jeep, and it doesn't even hiccup. Starts better than my modern vehicles, and with a tune-up you can't even hear it run. If your fuel pump hasn't been touched, now is a good time to rebuild that, too. Easy job, but make sure you get the right kit. At the risk of sounding redundant, check the throttle shaft. Cost me about $20 in parts for a shaft and screws. Idles smooth as a baby's bottom now. I was in a hurry and ended up doing the job three times, and as a heavy equipment mechanic with a good reputation, I am embarrassed to admit this. Best of luck.

 

YF carburetor flooding is strickly a gasoline supply issue.
Either too much pump pressure.
That's rather unlikely because the standard inlet valve should easily handle 5 PSI pressure.
If your inlet valve is vitron tipped then it obviously is not standard.
Or the other possible problem is improperly regulated fuel inlet control.
Make sure that the float floats.
Make sure that the float level is correct.
"Any" minute amount of debris can adversely effect the proper closing of the inlet valve.
A fuel filter at the carburetor inlet is ideal for eliminating any such debris.
The valve itself must be of correct orfice diameter.
.077 is the standard inlet orfice .
The original spring loaded valves and seats were brass on brass with a spring loaded damper.
The spring damper absorbs off road vibrations.
But the 134 should handle well made valves up to .088 orfice diameter if Hurricane is mostly used at high rpm.
The only aftermarket inlet valve I would ever consider is the Hygrade 518C.

 

Thanks everyone, sounds like I have some work to do. I'll let you know how it goes.

 

you said the leak is at the pump linkage? could the pump rubber be bad?