F-134 Just Doesn't Want To Idle

Help! I have a 1961 CJ-5 I am restoring and I am at my absolute limit on troubleshooting an engine problem. The I acquired the Jeep, it was not running. It has great compression across all the cylinders and I adjusted the valves. Put new bushings in the distributor and replaced plugs, cap, rotor, condenser and plug wires. I also rebuilt the Carb, replaced the fuel pump and verified the pcv system was working properly. The timing is set at 5 degrees BTC. The engine started easily with full choke but even fully warm, it surged terribly at idle. Acted like it had a horrible vacuum leak. There was play in the carb throttle shaft so I sent the carb to Vintage Jeeper for a complete rebuild and to have bushings installed. They sent me a video of it idling beautifully on their test engine.

Reinstalled on my motor, the problem improved, but still sputters and surges at idle unless the choke is on. With the choke on, the RPM's are high. As I reduce choke, the RPM's reduce and the unstable idle condition occurs I have blocked off the PCV port on the intake to eliminate the PCV valve as a possible vacuum leak, so maybe it is a low speed miss, or fuel starvation.

So I think you can see why I am so frustrated.

Any ideas? Replace the distributor with a new electronic one? Try another fuel pump? Idle mixture? Demonic possession?

 

The low-speed jet in the carb rebuild kit is probably under-sized. It needs to be .028", or a #70 drill bit.

 

Follow the guidance from post#2. This guy knows more about these carbs than probably anyone else alive today.
-Donny

 

X2! Scoutpilot, a.k.a. Rick Pacholski, is the owner of Old Jeep Carbs LLC. He rebuilt the carb on my GPW, and did a wonderful job on it.

 

Scoutpilot, thank you for taking the time to reply. That is what makes this site so useful. I will definitely check the jet, but the carb runs wonderfully on my rebuilder's test motor. I sent it back to him to re-check it and he sent me a video of him installing it and running it. Idles rock solid.

That is why I am so frustrated. Seems like a carb issue, but I think I have ruled it out from my testing. Totally baffled...

 

Welcome from Michigan. You must have a Vacuum leak somewhere, check the heater vacuum line, and the pcv valve, make sure there is no leaks. What kind of Fuel Pump do you have? What kind of wipers do you have? Just some suggestions Good Luck. Rick

 

If you have an early, vacuum-controlled heater control panel check it for leaks as well

 

3X. I'm pretty sure there is a vacuum leak someplace. I'd start by capping off the lines to the wipers and heater controls-after a close examination of the carb base gasket.

 

Thank you to everyone for the help! I am going to keep methodically working through this and your suggestions are helping me check my methods.

I have plugged the vacuum fitting under the carb so all of the PCV system is isolated. I don't have wipers yet, so I have that port on the combo fuel/vacuum pump plugged. I don't have a heater either. The fuel pump is a OMIX replacement and I have read that they are crap and some can struggle to pump enough fuel at low RPM's right out of the box, so am thinking of a test to prove that out. A friend suggested a rubber fuel line to the carb connected to a funnel held above the carb and let it gravity feed and see if the idle improves.

Another suggestion was to add a second carb base gasket to make sure vacuum is getting to the idle port on the carb base. Does that make any sense? I have verified I have the correct gasket with the slots in it.

I also disassembled the top of the carb and used a digital caliper on the metering rod. If anything it was just slightly bigger than .028 (.0282).

 

Take some carb cleaner while it is running and spray around the base and see if the idle picks up. If it does that is where there would be a vac leak.

 

Yes. The carb mounting ears can be bent by over-torquing, leading to an air leak. They can be filed flat again if necessary.

 

Well, I don't know if I found "THE" problem, but I definitely found "A" problem. Went to gap the points and could not get them closed enough to get to spec. Turned engine to the next lobe peak and found the points now too tight. Spun the engine and realized the shaft of the distributor is not straight and the rotor is wobbling. The bushings are not worn, the top of the shaft appears to be bent. Looks like I need a replacement. Any opinions on the Crown electronic units or the OMIX points replacement unit?

 

Yes. None good. But that's just me.

BTW a simple old fashioned dwell meter would probably have shown the points problem.

Rule #One - Can't do a carb tune-up until everything else is in-spec. First things first.

 

Both Crown and Omix are brands I will not use. Crown 25 years ago were mostly re-branded original parts, very good quality. Since then, they are hit-and-miss, more miss from what I have experienced.
Look for the brand of your original distributor, then place a WTB in the classified listing for a used original one, or a good used shaft if you you feel confident in rebuilding yours.
-Donny

 

Are you sure you have the correct distributor? Are you certain you have the correct points? We are all taking shots in the dark because we can't see what you are looking at.

 

Assume this 61 Jeep has the F134 ?

Not sure how a distributor shaft gets bent, but I suppose anything is possible. If your shaft is bent I don't think you can install an electronic ignition module without replacing the shaft or the entire unit.

One of my Jeeps had one of the electronic distributors from China. It worked fine, but I replaced it with a stock unit.

The reproduction breaker point distributors work fine if you toss the points, condenser, rotor and cap they come with and buy better quality components. I like "Blue Streak" points and condensers.

IMHO you would be better off money and quality wise finding a good used, or rebuilt, stock distributor.

 

x2.

 

Replacement Crown unit costs $119. Rebuildable distributor cores are going for $200. Rebuilt ready to run units going for $325. Original units with Petronix kits installed going for $450. I think I am going to take my chances on the Crown unit and buy three if I need to and still come out around the same place. Definitely the correct distributor, and the shaft is definitely bent. No idea what abuse caused that situation.

 

A small fraction of that, was my experience. Try advertising "WTB" on this site.