Hard starting when warm (too rich when starting)

[Newburn6]

Hi all,
I'm a new member of this forum and new to Jeeps. I bought an '86 CJ7 with the AMC 258 i6 / 4.2l ci. about a month ago in pretty good shape, but with some known issues that I will be working through very slowly. As far as I know (and from what the P.O. told me), the CJ is all stock.

The first issue I want to tackle is hard starting after the engine has warmed up. When cold, the engine fires right up and runs well. When warm however, starting is difficult. I'm pretty sure that it is too rich during this attempted hot start. It turns over well, it tries to 'catch' but it stumbles greatly and won't continue running unless at WOT. So, for the first 15-30 seconds, while at WOT it barely runs (I'd guess 400 rpm?), black smoke pours out, and won't maintain idle. The running slowly improves and as the rpms increase I can decrease the throttle until it clears up and it runs normally.

I need a bit of help getting started on the diagnosis. I'm not familiar with the carburetor, and don't know if vacuum lines play a role during starting. So, what sets the initial fuel amount for starting? Is it different when the engine is hot?

I hope some of you can provide a bit of insight into this. Any help is greatly appreciated.

Thanks

 

[Torxhead]

That carb is a Rochester BBD and the computer controls ignition timing and carb mixture. Look it up on the net. I would first look at ignition timing adjustment and a possible choke sticking.

 

[Lumpy Grits]

First thing you need is a copy of the REAL factory service manual(FSM).
That would be MR-252.
Haynes and Chilton are not very good.
Sounds like carb re-build time.
LG

 

[mtnwhlr]

So it sounds like after you shut it off it's flooding the carb. Two things, do you have a return line to the tank comming off the the fuel filter? You should have two lines off the back of the filter one to the carb the other goes to the tank. Make sure the return line is at 12:00. If all that is good than your needle and seat are weak and as LG said it's time for a rebuild.