The 223 I-6 idling in my stock 55 F-100 is becoming frustrating. Although I have set the idle and air/fuel mixture after the engine is warmed-up (which is idling great) however when I am cruising and come to a stop, the engine either dies or the idle drops really low to where it's barely running. Sometimes I have to pull the choke out real quick to keep it from dying. Any suggestions as to what could be possibly causing this? I have the stock system set-up, the carb was rebuilt a couple off years ago, new plastic fuel tank, and new fuel lines. Could a vacuum leak cause this? Appreciate the help.

 

Proper float level? Properly vented tank? Clean fuel filter? Distributor advance working properly? Good fuel pressure? Fuel line vapor lock from heat? Carb body not getting too hot (insulator between carb and manifold)? Charging system working properly? Heat riser working properly?
Just some things I can think of before my morning gallon of coffee.

 

I doubt a vacuum leak is the cause. Typically a vacuum leak is constant so cold or hot is the same. First thing I would check is what the fuel in the carburetor bowl looks like when the truck is running well then what it looks like when the truck is running rough (I'm assuming you have the glass bowl carb). My 53 sedan is temperamental about float adjustment and crud in the gas. If the float is too high, or your needle and seat don't seal, you engine runs terrible. You might also be getting vapor lock.

The other thought is that your fuel system is fine and you are having hot engine ignition issues.

 

Doesn't that carb have a diaphram that props the throttle plate open partially when you let off the pedal? Then when idle rpms are reached let's plate close. That not working or out of adjustment could cause similar problem.

 

Thanks. Unfortunately my glass bowl chipped at the corner so I had to replace it with a metal bowl. I believe my float was good for I adjusted it a bit lower than specified to prevent spillage into the manifold. You mention hot engine ignition issues-it does fine as long as I'm placing a load, it's the slowing down or stopping that's giving me fits. I have a low pressure 6 volt electric pump that I have been thinking about installing. I may try this out and see if this will help. I never thought the 223 would be prone to vapor lock but then again, the mechanical pump is taking heat from the block and it gets hot in Florida.

 

Mike, honestly, I'm not sure.

 

Does it idle OK once you restart it? Does it restart quickly? If so I'd just lower the float level a little at a time until it stops doing that.

 

Ross, it took a few attempts to get her started and when it did, the idle was much lower-I had to pull the choke out slightly to keep it from dying.

 

When it wants to die, do you feel the engine jerking and shaking around? It sounds like it could be running a little lean if you have to use the choke to keep it going. My gut feeling is the float setting may be a little too low. I had the same things happen with a rebuilt Holley. They never set the floats correctly, and even though it would accelerate and cruise great, every stop sign was a battle. I set the floats to just barely see fuel coming out of the bowl plugs, and in my case it fixed the problem. BTW, the carb I am talking about was not rebuilt by Holley, but was rebuilt by a third party.

 

I could be an electrical problem.
I used to have the same problem with my 54 223 but after I replaced some wiring that had worn insulation the problem went away.

 

Ross was also mentioning the float and when I get back in town, I will try doing that first and see if this takes care of it. I have a feeling that I may have set it a bit too low. Dang I wish my glass bowl didn't have a chip on the top corner! I will come back and report my findings.

 

Float settings on the bench are just a ballpark, it's the fuel height in the bowl that counts. Rebuilders can't really be faulted for that. Different fuel pumps, production tolerances of the floats, filters, &c are going to make the fuel height vary. Holley did really good with their center hung float design and being able to set it on the fly, just till it dribbles out of the screw hole on the bowl.

I'd try to figure out a way to use the clear bowl, at least for test purposes, to get the fuel height correct. Then reinstall the "good" bowl cover or whatever.

 

To keep it running, are you pulling out the choke just enough to jack up the idle? or pulling it completely out?

 

Very little-just enough to jack up the idle.

 

Does t have a decent return spring on the accelerator linkage ?
When it's idling ok , can you move the linkage enough to drop the idle and make it run rough ?
The problem may just be in the linkage if it runs and drives ok ?