Rochester 2g Problems

Hi everyone. I did a full frame off restoration on my 67 V6 CJ5 2 years ago and have had a problem with the 2G since. The one that I originally rebuilt and installed was dripping out of the Venturi on light throttle but idled fine and ran fine at full throttle. I rebuilt another 2G I had laying around and it did the same thing. After 2 years, I've changed the fuel pump to one with a return which lowered the fuel pressure to 4.5 lbs which is the correct spec I've found. I've rebuilt the carburetor again but this time using an ultrasonic cleaner and it looked perfectly clean. I chased every hole with wire and blew it out. I reassembled and same problem. I tried a new brass foot instead of Nitrophyl. I submerged it in hot water to check for leaks and nothing. Put it in at correct spec and still dripping. I tried messing with the float height and no difference. Needle and seat it sealing. I'm completely at a loss and have no idea what else I could possibly be missing. It's not that complicated of a carburetor but there must be something I missed. Any ideas would be greatly appreciated.

-Jared

 

Checked the power valve before I installed it and it wasn’t hanging up. Moved freely by hand and the gasket was installed underneath it. One ball is in the accelerator pump and the other goes under the Venturi. Both were installed. It’s a puzzler for sure.

 

The only way to get fuel through the venturi is either vacuum or pressure.

Pressure (excessive float height) would cause flooding when idling, so I would discount this.

Other than observation, does the engine run well? Is the fuel dripping at all throttle openings or only at light throttle?

I'm thinking it is a transition issue. The carb is coming off the idle circuit and onto the main metering system early. The air volume isn't enough to atomize the fuel yet so it is coming out in liquid form. Check your timing. retarded timing causes the throttle plates to be further open to keep the engine idling. This can cause the engine to transition to the mains much earlier.

 

The fuel only drips when the engine is under light load meaning just driving down the road. It does not drip when it is idling and it runs beautifully otherwise and winds out wide open just fine. Timing is exactly on spec for the Delco distributor. I swapped the distributor out with a Prestolite I had rebuilt and it made no difference. I also thought it could be a timing/ignition issue but swapping distributors would've changed something and it didn't.

 

Needle and seat were checked before I finished the rebuild and they're sealing fine. The check in the power valve is moving freely. Just checked that again today.

 

Maybe there might be something in this manual that will help find the problem.

http://www.hdts.vcn.com/JEEP/ROCHESTER 2G, 2GC CARB.pdf

Good luck
Mike

 

In case you decide you want to get yours professionally rebuilt, I had my 2G done last year by a guy in NC, Jeff Dreibus "The Old Carb Doctor", who did an absolutely fantastic job on it. I'd rebuilt mine myself many years prior, but his work went well beyond simply rebuilding it again. Among many other improvements, this included bushing the throttle shaft, closing up some other vacuum leaks the 2G's tended to have issues with, and drilling out the metering jets slightly in order to account for the differences in the fuel that's currently available vs. the gasoline in the 1960's. My V6 has never run as well as it does now following his carb rebuild.

Total cost was around $400. The only (other) downside I know of is that he stays in high demand, so his backlog tends to run several months out. Here's a link to his website:

Old Carb Doctor

The way it works with Jeff is that you'd first need to send him a $100 deposit in order to get on his waiting list. Using part of the deposit, he'll order a Walker rebuild kit for your carburetor. He'll let you know when he's nearing the point of being ready to work on it - likely several months later - and you send it to him then. The turn-around time from that point is/was fairly quick.

 

hello, welcome to this gathering place of enthusiasts! i dont have any knowledge of this, but these guys know their stuff.