Carb leaking at base

Hi I have a motorcraft 2150 on my 304 and it is leaking around the base gasket. I have a feeling that fuel is getting out of the bowl or from somewhere. Does anyone know how easy it is to fix this. After the jeep sits for a couple of days I notice it running down the side of the manifold. It's not leaking from the linkage. I got down there with a good flashlight. It also has a hard time starting after sitting a few days, like there is no fuel in the bowl( I give it a pump it fires right off then dies....then it takes several cranks to get fuel to it before it fires). Any help would be greatly appreciated. Thanks Ryan

 

I'd guess it's leaking through the power valve and maybe out the power valve cover. The PV is directly under the float bowl, so AFAIK this is the only path where fuel can drain from the bowl by gravity. Ruptured PV diaphragms, caused by backfire, are very common for these carbs. If the PV cover is not leaking but the PVD is ruptured, fuel should drain from the float bowl and out through the manifold vacuum port (see figures 5 & 7 here: http://www.c104.net/manual/Section_04.pdf ). If your base gasket leaks, the liquid fuel could seep out onto the manifold.

I'd suggest you check/replace the PV, PV cover gasket, and base gaskets. Unfortunately, a '78 from CA likely has a 2-stage PV, which is available separately from Napa IIRC, but expensive at about $25.

hth!

 

Also, you're sure it's a 2150 and not a 2100? I would have guessed that the '78 CJ has a 2100. I have a CA carb from a Cherokee on my pickup, and it's a 2100.

The 2150 has a vacuum hose on the PV cover that supplies manifold vacuum IIRC. The 2100 will have the manifold vacuum port to the PV in the carb base. If you can post a pic of the top of the carb with the air cleaner off, I can ID it.

 

Timgr - Thanks and I have a huge amount of respect for you. I am continually amazed at your knowledge! I think it's a great thing that you help so many of us on the forum. Here's to you And a big THANK YOU I will post a pic as soon as I can. Ryan

 

Here's that pic.

 

To the best of my knowledge, it's a 2100. The choke pull-off on the air horn is a positive ID. If it were a 2150, it would have an external choke pull-off.

Courtesy Pony Carbs:


hth!

 

Did Autolite make the 2100 and Motorcraft make the 2150?

 

Yes. And Motorcraft made the 2100 too.

Motorcraft is Autolite. Not sure of the details, but Ford called all of their parts "Autolite" until some time in the 60s or 70s, then they started to split the electrical stuff ("Autolite") from the rest of the parts ("Motorcraft"). There's probably more to it, but you'll have to ask some Ford fanatic for a more complete story.

BTW that's a really early 2100 in the Pony Carbs picture above - maybe 1961, 1962 or thereabouts (guessing).

 

This may be a dumb question, but when I compare mine to the two pictured. It has features like the 2150 above the bowl. The back of the carb is more like the 2100. Why is this?? I checked with the parts guy at Kragen and it lists a 2100. Thanks Timgr.

 

Yes. Don't be confused. I included the picture as an example of the outboard choke pull-off. Only the 2150 has that. Your carb looks just like the 2100 that I adapted to my pickup - it came from a '79 CA Cherokee. The 2100 in the Pony Carbs picture is reeealy early, with an open bowl vent. Your carb has a bowl vent that connects to the vapor control can, which is typical of the era. The 2150 has a similar connection to the vap can, but does not have the choke pull-off on the top of the air horn. Do you see this? It's the diaphragm thing with three screws. The 2150 does not have this.

 

So the reason the vent is similar to the 2150 is for smog purposes...it catches the gas vapors from the bowl. So the 2150 was developed later which would have more smog controls than the early 2100. This makes good sense. The choke pull off is pretty easy to see the difference between the two. Thanks Again Ryan

 

Go Holley!

 

Update....upon closer inspection. I could clearly see that the powervalve gasket was not leaking. I checked the base mounting bolts and the right rear was loose. So I now know where the fuel is coming from. My next question is why would it tend to collect and drip down only after sitting. My thought process is with the engine off. Fuel should not continue to flow. So where inside the carb would it allow fuel to continue to flow after the engine is off?

 

It's draining the float bowl through the power valve vacuum port (I suspect). See the pictures in the manual above.

 

Another update I rebuilt the carb and it runs much better. I had a post earlier about off idle stumble. I thought I had that problem solved after adjusting the timing, but there was still a slight stumble as I just started to accelerate, this went on for a couple of months until I noticed the fuel on the manifold coming from the base of the carb. Timgr you were right about the powervalve being the culprit. No more hesitancy off idle. This should now have fixed the fuel draining from the bowl. I will see after she sits for a few days and double check the manifold and also pay attention to it's starting habits after sitting. Should all be fixed Thanks again.

 

Latest update...I checked the oil after driving it a couple of weeks. It looks like the fuel isn't draining into the oil anymore...still nice a clean. The jeep is still hard to start after sitting several days. I need to take off the top of the carb and see if there is still fuel in the bowl. I have a hunch that it is draining back through the float valve into the fuel line. I was unable to replace that because the threads were different on the cab kit.

 

Sounds like the '78 needs a matching MegaSquirt in it.

 

It does, but I can't smog it with the megasquirt. Howell does make a kit, but that would set me back 1.2k. I am having fun driving it anyways

 

Hmm. I doubt that. Unless the seat (of the needle valve) is leaking at its base, fuel would have to run uphill to drain back from the bowl. Even then, the bowl would not drain completely. More likely the fuel is evaporating. If the carburetor top seal is not good, or if you leave the air cleaner off, fuel will evaporate from the bowl more quickly.