Carb fuel leak

[thistle3585]

The problem is that I have a raw fuel smell and am having to crank the engine awhile before it will start.

I'm not sure if I have the right terminology so bear with me. (I would appreciate if someone can give me the correct terms.) I have a metal plate that attaches to the top of the engine with bolts that protrude which my MC2100 mounts to. Between the engine and the plate there is a thin paper gasket. Between the plate and the carburetor there is a 3/16" gasket. The 3/16" gasket slightly extends beyond the carb and it is completely saturated with fuel. That's where the raw fuel smell is coming from. I'm also guessing this is contributing to the start problem. My question is what should that gasket material be made of and/or should I use a sealant with it?

 

[Lumpy Grits]

MC2100 is well known for this.
IMO-they are more trouble than worth.
Go to NAPA and tell'em you need a sheet of fuel resistant gasket material and then make your own.
LG

 

[thistle3585]

Thanks. After further investigation, it looks like it is leaking where the throttle shaft goes in to the carb body.

 

[Lumpy Grits]

Check your float level.
LG

 

[thistle3585]

I checked it and it was spot on per the specs, but I did notice that the needle valve wasn't seating well so fuel continued to "bubble in" to the bowl until all the pressure in the fuel line dropped to zero. I have an inline fuel pressure gauge, so I was able to watch it. It looks like I'm going to need to pull the needle valve out and check it. I'm thinking there must be some debris in it that is keeping it from closing completely.

 

[Lumpy Grits]

Replace the needle and seat. It's only gonna get worst.
When was the last time the carb was rebuilt?
LG

 

[thistle3585]

Actually, I had just rebuilt it about two months ago so I'm sure its my fault. I had been going back and forth between two different carbs trying to decide on which one to use on my new motor.

 

[Lumpy Grits]

FIX-IT ASAP!
You have a real fire hazard on your hands.
Good luck,
LG

 

[Dan77CJ7]

Are you running a fuel pressure reg?

 

[Dan77CJ7]

the gasket between the intake an the adapter plate should be thick both my gaskets are thick i'll get the part number for the lower gasket but i dont know if it fits ur intake. i have my pressure set at 3-3.5psi as per usual the fuel filter close to the carb, return clocked at 12.

 

[thistle3585]

I put a new engine in and failed to pull the adapter plate off the old one before selling it. The studs on the one that came with the motor are too short to put anything ore than the 3/16" gasket on. I guess I should look in to a new adapter plate.

From the fuel pump, I have an inline gauge, the filter then the carb. I also have a filter before the fuel pump. The pressure reads 5.5-6 on the gauge. Although I'm driving a '79 the engine is out of a '72.

 

[hdgapeach]

Replace the studs with longer ones. Cheaper than buying a new adapter (unless the one you have just won't get it done).

 

[DHugg]

"I put a new engine in and failed to pull the adapter plate off the old one before selling it. The studs on the one that came with the motor are too short to put anything ore than the 3/16" gasket on. I guess I should look in to a new adapter plate.

Read more: http://www.jeep-cj.com/forums/f2/carb-fuel-leak-22143/index2.html#ixzz2zvrm5hjx "

New longer studs!!! I make a run to the local bolt and nut place almost once a week. You can also use VersaChem Prime Seal type 3 Aviation Sealant. Airplane mechanics have to tear down engines much more often than even Jeepers. Having to scrape off old gaskets bonded to metal surfaces is a downer. Prime Seal type 3 on application is about molasses-thick, but sets up to dried pine sap or sweet gum goo (sorry for you non-country-raised people, but I only know what I was taught). It'll separate without ripping the gasket to pieces, and you can clean the surface to bare metal again with a solvent.

I have half a can left after sealing up a Dana 300 and a TF999 belly pan. So far not a drop of leak in two years.

​

 

[hdgapeach]

Love the stuff. Works great. Used to use it sealing VW engine case halves together back when I tinkered on air cooled bug engines. NEVER had a leak show up.

 

[thistle3585]

Pulled the carb off this morning along with the fuel filter. The filter is a clear one and I noticed the filter inside the canister had dislodged from the side so it wasn't doing a good job of filtering. I'm guessing some debris had gotten in there and not letting the valve seat. I'm going to clean it out and reinstall and go from there. Also going to look for new studs.