Rochester 2G won't idle and stalls if not partially choked

Full disclosure, this is actually on a 71 Jeepster but I know this forum gets more traffic and it's same same anyway

Here's the backstory: I have had this Jeepster for years. Finally getting it on the road. New plugs (plugs look good after my initial tuning), new plug wires, pertronix installed in distributor, timing set, rebuild carb by a reputable shop in California. etc. etc. etc.

Here's the symptoms: Jeep will start when cold and when the throttle is on the fast-idle cam. Runs pretty well while warming up at high rpm idle (don't know how high, no tach) As the Jeep warms up and the choke plate opens (electric choke conversion) and the throttle comes off the fast-idle cam it won't stay running. I sprayed some carb cleaner around the base of the carb, etc. and don't seem to have an vacuum leaks.

I turned both idle mixture screws to 1.5 turns out. That didn't have much effect.

I did notice in my experimenting that if I keep the choke plate about 1/3 way closed it will stay idling at a much lower idle than the fast-idle. If I try to drive it around the neighborhood, it stalls out and dies at every stop sign, I can't push in the clutch and press the brake or it will die. I need to keep feathering the throttle with my foot that is on the brake. Thanks for reading this far. I really want this bad boy on the road. My 16 year old is going to drive it to school. He's a kid so it needs to start right up and stay running at stop lights.

Mike

 

Water or crud, causing lean mix?

Try using a can of Seafoam in the gas tank. But if it's been un-used all those years a simple carb re-hab might be in order.

Also, be sure you are not being misled by points or timing being off. A basic tune up "to spec" is a good idea before trying any diagnosis.

 

I forgot to add. Tank freshly washed inside with white vinegar, new feed and return lines, new fuel pump, glass fuel filter, clean gas.

 

set the idle screws with a vacume gauge. turn them in till it starts stubling then out till its smooth and at highest vacume

 

I can't get it to idle well enough to set the mixture with a vacuum gauge.

 

Have you checked for a vacuum leak? Classic symptoms. If you have the stock heater with the vacuum controls, that assembly would be the first place I would be looking.

 

Certainly could be. Check the vacuum lines,if any.

But I'd still want to see what the inside of the float bowl looks like. Just cleaning out the accumulated crud in there has sometimes worked for me on negelected vehicles.

And I've sometimes had similar symptoms when distributor points oxidize over the winter, or the gap is excessive.

 

^^ This first.

Plug all vacuum ports and start from there.

Is your idle just not adjusted high enough to begin with, or does it have that classic "lean idle" symptom of idles-for-a-second-then-drops-off-and-stalls? What happens if you just adjust the idle higher?

Does it have the dash pot?

 

Where are the lines running into that?

 

It idles for a second then drops off and stalls. If I adjust the idle really high it will run and if the choke is partially closed it will run.

 

The back of the carb has a T fitting with a huge (1/2") nipple that is capped off. The other side is the T goes into the PCV assembly. Should I replace that T with an elbow and eliminate the big port going nowhere? Does the PCV need manifold and carb vacuum both?

Would it be beneficial to check the float level? I am happy to go back to zero and start from the beginning.

 

Like ITLKSEZ said, plug all the vacuum ports. I haven't looked at a stock intake manifold in ages but think it is just like the Offy on mine, with a manifold NPT port behind the carb. Preferably, put a pipe plug in it to test but a rubber stopper may also do the trick. Those rubber lines always crack with time where they plug into the heater control. Best to replace but sometimes you can cut 3/4" off the end and put them back on. About the only other items I can think of would be the vacuum advance and the PCV hoses

 

Or maybe a stuck PCV valve? Definitely sounds like a vacuum issue.

If no change with plugged vacuum lines, try backing the carb screws out about 3 1/2 turns. If it runs then, turn them in until it starts to stumble again, then back out 1/4 turn from where it began to stumble.

 

You should open the carb any way.

But, I may have missed it, Do you have a vacuum booster on your brakes?

 

Update: Opened the carb. It wasn't dirty but it's spotless now. Removed carb from manifold, cleaned gasket surface and replaced gasket. Removed throttle body from carburetor bowl and cleaned those surfaces and replaced gasket. Removed Venturi, ran small wire down all the holes, replaced gasket. Removed jets and wiped clean, checked float settings. Reassembled everything. Plugged top vacuum port with new rubber cap, put new cap on threaded bottom of choke housing on side of carb. I am positive there is no vacuum leak from the carb and that the carb is clean.

No change.

Next step: PCV valve, grommet in valve cover and hoses?

Thanks guys

 

If you didn't plug PCV the line in your attempts, just pull the PCV valve out and hold your thumb on it, see if that makes a massive difference or not.

Did you try backing out the screws up front?

 

At least now you can be sure the carb is clean, before looking elsewhere.