No power under a load when cold

[blaylock6502]

I have a 74 CJ5 with a AMC 258 i6 / 4.2l and manual three speed. I was having some trouble with a hesitation when under a heavy load and a guy I work with told me to bring it into work. I am a technician at a gm dealer but being 28 carbs and points ignition may as well be an alien spacecraft. He looked at the carb and said it could be due to looseness in the throttle plate shaft so I bought a new carb. I ordered the factory one barrel replacement carter but when I got it I realized it had a two barrel on it with an aftermarket edelbrock intake. Fyi it has a hedman header if it makes a difference. He thought it would be fine as I just wanted it to run descent and wasn't really concerned with power so I got an adapter.and put it on. I set the dwell and timing and then he adjusted the carb. When I drove it home it was ok but the next time I started it cold it felt like it wasn't going to get out of its own way. As it warmed up it get much better. I thought maybe the choke was sticking but it wasn't. Any ideas. I put new points on and set the dwell and thought it was fixed but the next time I started it cold it was the same thing. Any help is greatly appreciated.

 

[CJ]

Re: Now power under a load when cold

So many things to figure out!

From the beginning now,

When you drive off cold what are the results?

When you drive off cold what are the results?

 

[blaylock6502]

When I take off cold if I ease into it I can tell it s lacking power but when I get into it a little it falls on its face and starts to backfire one it reaches what I would guess to be 2000 rpm it clears up and takes off. When its warm it runs great

 

[mtnwhlr]

Re: Now power under a load when cold

Sounds like a motor with a carb. If you don't want that you need to go fuel injection.

 

[blaylock6502]

If that's normal that's good with me. Should the choke be coming on with it being upper 60s lower 70s

 

[mtnwhlr]

Re: Now power under a load when cold

The choke goes by motor temp not outside temp. So it will close when ever the motor is cold no matter how warm it is outside.

 

[blaylock6502]

So what ur saying is the choke should be closed whenever the engine is cool regardless of ambient temp?

 

[mtnwhlr]

Yes

 

[blaylock6502]

Awesome ill try that. Thanks for the info

 

[jasonmark1993]

Do you have an electric choke?

I agree with the guy above. Cold engines need a richer mixture so just add some choke and you should feel improvement.

 

[tarry99]

If its a mechanical spring loaded it should not be "Fully Closed" there is a ramp on the linkage that should allow the choke blade to open a little on a cold start. Then as the motor is running heat is transferred to the choke can and it gradually opens full.
Like wise if it has an electric wire to it when the key is turned on a solenoid sets the blade partially open.

 

[blaylock6502]

Its a climatic choke. I adjusted it to be about halfway closed and took off cold and it seems alot better. I am on vacation now so cant wait to get home and try it again

 

[tarry99]

Sounds good, some choke butter fly's have a slot or hole in them and that is just to allow some Oxygen in so it doesn't flood the motor. In either case they should be partially open on a cold start.