Rough/tough idle when hot

I've read through a LOT of threads, but still not sure how to proceed.

My Jeep (66 CJ5 / 225 / Rochester 2G / Delco distributor with points) seems to start up immediately and idle fine in the driveway for as long as will let it sit. Yesterday, I drove it to pick up my son at school in the carpool line - 5 minute drive over there - and, while I was in line, it began idling very rough and eventually would not sustain an idle at all. Unless I kept my foot on the gas, it would quit. And then it was extremely hard to get started again. I finally could not get it to re-start (holding up the whole line and embarrassing my son, which is :twisted.

Last night, took the wife's van over and it started right up. Left it there (wife threatened me if I left the van there) for the night.

She dropped me off there this AM to pick it up - started right up, I drove it home and immediately checked the dwell, timing, idle, vacuum at idle (18-20 at 2.25 turns out on the screws), etc. - all looks good. Fuel is definitely getting through the see-through fuel filter just fine. It sat there and idled for quite some time - smooth as it can.

Decided to take it for a test drive - drove maybe 5 min and came to a stop and it is idling rough again ... next stop it quit. Very hard to re-start - same as before - crank and crank and crank and finally it will barely start to stumble and if I can catch it right with the gas it will spin up and run at a very high idle, but will stall if I take my foot off of the gas. Runs fine as long as I am on the gas, but no idle. Finally got it home, but had to run in for a conference call for work.

Went back out a few hours later and cranked right up, but pretty quickly got back to the same problem. Choke seems to help if I pull it out 1/3 way, but only because it gets it to a very high idle speed. I have tried every setting on the idle mixture screws from 1 turn out to 3 turns in 1/4 turn increments, and while the area from 2-3 turns out seems to run better, it still has the rough idle to eventual stall issue no matter what.

I did rebuild the carb, and followed the instructions meticulously, but am questioning whether or not I did something wrong now.

One thing I did notice is that I am getting 14V on one side of the Ballast Resistor and 10.5V or so on the other side. Is that too high?

Any ideas? I can take video and/or pics if that would help troubleshoot.

 

The voltage on the ballast is not bad but will probably drop a little more as it gets hotter. Somewhere around 8.5 to 9. I am leaning towards maybe a condenser going bad. Did you change plugs during carb rebuild? Did you maybe get hold of some bad gas? Too much water? HTH

 

When I rebuilt the carb, I completely cleaned and sealed the gas tank with a POR 15 kit, replaced the fuel lines and fuel filter, replaced the plugs (made sure gap was good), plug wires, coil, points, condenser, rotor, and cap. And the ballast resistor. It's all new.

 

On your new coil - - It is marked (FOR USE WITH EXTERNAL RESISTOR) RIGHT??

 

So it seems like something is getting hot and not working - check and double check the coil and condenser even though they're new.

Also check the fuel filter in the line and the one at the carb inlet.

Also check the electrical connections in the ignition circuit. Especially the main engine wiring harness near the passenger side valve cover.

To get more creative to find the problem maybe you could install a fuel pressure gauge at the line to the carb and see if you're losing pressure? And maybe take a voltage reading at the coil to see if there's a difference between when it's running good and bad.

Also you may want to check your vacuum - good excuse to buy a vacuum gauge if you don't already have one.

Post when you get it figured out.

 

spray around the base plate with carb cleaner while running to see if carb to intake is bad.

 

I had a similar problem on a Ford truck with a motorcraft 2bbl once. Turns out the carb itself was getting too hot causing the fuel in the bowl to boil / vaporize. If I drove it even a short distance then shut it off for a few minutes it would act just like you describe. I added an insulator spacer between the carb and intake and the problem went away.

 

Hmmmmm - I did get a thicker "foam looking" gasket in the rebuild kit - maybe 1/4 inch thick. Maybe I can try that instead of the thin paper-type gasket?

 

you may also check the fuel pump. diaphragm pumps will lose presser when hot but run fine when cooled or at idle

 

I agree with Toolmaker. I think you have a fuel issue. Either as he described or a vapor lock issue. Are any of the fuel lines near anything hot? And definately use the spacer.

Are you sure the tank is vented? Next time it does this, run back and unscrew the fuel tank cap and see if it runs. I had a boat the same thing happened too. As long as it was at idle, it ran great. Soon as it got up to speed and started pulling fuel out of the tank, very quickly the gas leaving was just a bit more than the air comming in the tank to replace the gas. As soon as I vented the tank by unsrewing the cap a little bit, it was fine.

These are the two areas I would start with.

 

make sure it is the proper gasket and seals everything not like this ,gasket shrunk and was exposing areas(left side- the real problem ) I use the a gm gasket now and not the one that comes with the kit.

 

I bought a new fuel pump with the return capability and ran a return line back to the tank. I did run the lines up over the engine like stock. I'll see if I have enough rubber line to run along the frame rail to the fuel pump as a test.

Hmmmm - I'll have to check that.

 

Made some vids for you guys. In vid 1 - seems that the fuel is "dribbling" in - shouldn't it be more of a spray, I mean more atomized?

I talked to one "carb guy" he says my float may be off?

Just talked to another carb guy and he says I didn't get all of the varnish out when I cleaned it?

Sounds like I need to pull it off, take it apart, and check it.

Take a look at my vids:

http://www.youtube.com/watch?v=LimbrQB4KLE

http://www.youtube.com/watch?v=-9See-8bIWs

http://www.youtube.com/watch?v=KrTE6XJp864

 

From what I see in the first vid you have a lot of fuel pouring out one main metering jet. Is it coming out both? I may just be seeing the video wrong but you sound like you are also are seeing a lot of fuel that should be atomized.

Tom

 

Looked at it again, and it looks like the "dribble" (i.e. not atomized fuel dribbling in - more than a drip) is only on the passenger side. I don't see it at all on the driver's side. What would cause this dribble rather than normal atomization?

Where is the best place to buy the highest quality rebuilt (as good as or better than new) 2G?

 

Others will probably have better info than I have but going from memory those metering jets (where I think you are seeing the drops) control flow via a small air bleed below the bottom throttle butterfly combined with your mixture screw. You might want to re-check your mixture needle settings on both sides plus pull them and make sure no little crud got in there by shooting some carb cleaner in the needle hole and watching for flow down into the carb throat.

The thing thats not making sense to me is that this seems temp related. Have to think through that correlation because I don't see how that could be happening unless the intake manifold is getting very hot.

Do you still have the original butterfly valve on the passenger side exhaust pipe? If its stuck it will direct hot air up to pre-heat the intake manifold but your exhaust notes on each side seemed normal so I doubt thats it.

 

Not sure it is temp related - the more I work with it. I have headers, so no butterfly valve.

Anyone know a place to get a top condition rebuilt 2G? I think I am just going to replace this one and move on. Wife is getting ancy that the Jeep is "unreliable" ... my son can't keep his mouth shut abt the thing stalling in the carpool line ...