!954 truck 239 ohv. Original carb that has just been rebuilt new plugs and wires. When I pull manual choke half way out truck runs great and revs fine. Push choke in and truck runs for a few seconds then dies. Any ideas? Thanks

 

First guess is the carb is running too lean. Need to adjust the mixture.

 

Vacuum leak?

 

I would also check the timing, when the choke is out your at a higher RPM and you might have the advance kicking in allowing it to run but it’s dead without the advance at idle.

did you adjust the idle mixture screws?

Chris

 

I believe you have to go thru the carb unless it has been rebuilt recently. Or if it has been rebuilt maybe the float wasn't set properly. It is too lean most likely. Todays gas really gums stuff up. That's my long distance guess!! Good luck, let us know how it comes out!

 

Pulling the choke out, and it runs fine, push choke in and runs like crap or dies: Its starving for fuel period. First quick check, take the top off, the fuel level has to be up /
float up and level. Yes or no? So if fuel is up and level its venture'y time. Take carb off
to the bench put carb over a container fill fuel bowl put top back on, holding throttle
plates wide open now blow shop air maybe 15- 20 psi down its throat; you now should
see a nice fuel mist coming out of the venturies both of them if not, still on the bench take venturies off, two screws and blow that out good cause something got in there. Idle air adjustments has nothing to do with this, only for smooth idle. A vacuum leak
has to be pretty major, like power brake hose ruptured or intake gasket witch I doubt.
And even if a wiper vac line is leaking all that will do is effect the idle. Distrubutor vac has nothing to do with your problem . Recap; a running engine sucks vacuum through the air cleaner, this vacuum sucks or draws fuel through venturies that come from the main jets, the venturies meter this fuel through little tiny holes and
takes only a piece of dust / dirt, could even be so small as lint from your shirt. So all carb's we rebuild we shoot the shop air down its throat. See the equal mist (atomizing) bet my life that's ya problem. Don't loose sleep can do with flashlight on
the engine off ''''''throttle open squirt shop air down there should be two nice misting's
Is this clear as 'mud' also check the power valve and or gasket sam

 

When you say blow air down the throat do I just open throttle plates and get a air gun and just blow it in side the carb. Sorry just a little confused. Thanks everyone for responding as I would love to get it going.

 

Just something real simple that I think everyone overlooked. Did you adjust the idle speed?

when you open the choke on a Holley 94 it opens the throttle a bit to a fast idle but you lose that when you close the choke.

some volt meters have a tach function, same with some timing lights if the truck does not have an aftermarket tach.

 

Here is an old school chart that might help you with your old school truck:

 

All good advice here, if you want more, start with the easiest things first, before you go taking everything apart. Most likely the problem is with your idle mixture screw and or the idle screw, especially where the thing was just rebuilt and those things would have been taken off as part of that process. I think the default starting point for the idle screw is somewhere around 1 1/2 to 2 turns out (it will need adjusting from there) and you need to make sure that your idle screw is actually doing something to the throttle. I'd start by turning it out to see if it's even pushing on the throttle arm at all. Even if it is, you can turn it out to crack the throttle more and see what happens. If it's racing when you get it to go, then the idle needless to say is too high, turn it back down until you reach a reasonable idle. If it dies when it gets down to a reasonable idle, then it's either the mix screw or something along the lines of what the others are saying. It's possible that a mistake was made when the carb was rebuilt, human error does happen. But before tearing it all apart, do some of the easy stuff first, start with a screwdriver, and that might be all you need to do. If you get it idling, I highly recommend adjusting your timing and idle mix with a vacuum gauge, I'd never done it before and it sounded like witchcraft to me.... I just did it last week, and it was not only easy, it really helped me get it dialed in better. I also realized how far off I had my timing set, and I thought the thing was running fine. There is a LOT of leeway in some of these motors. BTW, I have the 223, so I think it uses a different carb, but I think they're pretty similar.

On another diagnostic side note, have you ever had it running before? I think we're all assuming that you were using it, then rebuilt the carb, and now it's not running. There could be a number of things that cause that to happen.

Good luck!