This is my first carburetored vehicle so this may not be an issue. I have a 77 F100 with a 302 with a 2150 carburetor (was replaced earlier in the year) . I just went through the adjustment steps listed here https://www.ford-trucks.com/forums/7...ml#post6422219. The truck starts and idles just fine with vacuum constantly around 18-20 psi. When the truck is fully warmed up it the choke doesn't seem to be opening/releasing completely. When I Rev it the choke barely opens to about 1/4 inch open. Still the truck runs fine and will start sometimes a little difficult almost like puttering but eventually it will start. The choke is automatic with a heat pipe from the intake manifold(the heat pipe has been recently replaced). The temperature where I'm at is around 45f so that may be the cause. So my question is the carburetor properly configured and running right.

 

Look on the passenger side back of the carb. There is a round puck with a vacuum line hooked up to it and linkage It's going to the choke. Its called the choke pull off diaphragm. Just found out that mines bad. Choke never opens fully and the idle never drops down. Hope this helps.

 

When I try to squeeze that vacuum assist all of the way in it seems to stop before going all of the way it. I'll look for replacement and hope that works. Thanks
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A 2150 owner should be able to provide more accurate information than I, but I will say that I was never able to get the automatic choke to work properly on my 4350, so I converted to a manual choke, and it's never run so well. It will close completely when needed and open completely after warming the engine.

 

I have the same issue here. my vacuum is about 18 when the gauge is hooked up.
it never opens fully. it actually only opens about 1/4 inch max.
I have been looking on youtube and reading all I can but just
cant seem to find the fix.

I hope we can get pointed in the proper direction to setup and or fix our choke and choke pull off.

 

I have adjusted the choke pulloff some more, which allows the choke to be opened a bit further. When I rev up the engine the choke only opens a little bit more. Its closer to being in the fully open position but still has some distance to make. so it seems like the choke pulloff is working at least.

 

I adjusted mine a little. it did not do much of anything at all. it only opened the choke a tiny bit more.
I know its not hard to adjust a carb in general, but I am at the point of just going Sniper EFI...

 

If the pull-off will hold vacuum, it's still good. Pulling the vacuum hose off, pressing the plunger inward and covering the vacuum port with a finger will tell the tale usually. If the plunger stays in, the diaphragm is holding a vacuum and is fine. If the plunger releases even with your finger over the hole then there is a leak and it needs to be replaced.
There are still adjustments that need to be made, but if it's not holding vacuum then none of the adjustments are going to do anything.

The main job of the pull-off as I understand it is to set the initial cold position of the choke plate. I was not aware it had anything at all to do with the plate opening all the way when warm. That's why there is a huge long slot in the plunger. Once the pull-off pulls the choke open that first 1/4 inch or so, the choke coil takes over from there and pulls the choke open farther and farther no matter where the pull-off is adjusted.

A '77 would have an electric choke that is powered up by the alternator's White w/black stator circuit. If your truck has the full gauge instrument cluster with the ammeter, with only the three wire positions at the voltage regulator filled, then the choke is the only purpose of the stator wire.
The heated choke coils will fail too. Not as often as other parts perhaps, but after more than 40 years anything is possible.
The choke coil is also adjustable for full pull if it's still working. Once you verify that the coil is heating up and pulling the choke off/open, loosen the three screws and rotate the housing until the choke is pulled open.
Since you did all the adjustments per that other information, I'm assuming you checked the adjustment of the choke mechanism itself, and set the base adjustment to whatever notch was recommended. But did you verify that the coil was being heated and was still working?

I'm not sure what voltage you should see exactly (it's less than 12v) but with the engine running you should be able to get a reading off of the connector there at the choke where the White w/black wire attaches.
See what that is reading and let us know. Maybe the stator circuit is dying and you're only getting a couple of volts there? Maybe it's just engine heat that is opening things up at this point.
How long does it take for the choke plate to pull off to it's max open point right now?

Paul

 

My choke is automatic and I believe my issue is with my thermostatic spring. When the truck is warming up the choke never starts to open and I went though all of the adjustment steps once again, which had no effect. If I could find a replacement locally would be great but none of the stores carry it. I'll update everyone once the part is replaced and to verify it was the issue after all.

 

There is a heat tube plumbed into the choke assembly . Quite often this heat tube is rotted away. It is supposed to go from a plate in the intake manifold up to the choke and is supposed to heat the choke spring to help the choke fully open. I have never been able to find a replacement.

 

I have just installed a new heat pipe. I used 1/4 inch brake line and ran it myself. The tube passes air easily and warms up during idle. I do not believe that is the issue. I have a replacement spring coming in tomorrow so I will see if that fixes the issue.

 

Not to hi-jack but I had to repair my heat tube.
once that was fixed it now opens all the way.
I now need to get it tuned properly. I believe
my engine is not in good shape. vacuum was
lower than I thought. it is at about 14 at idle.
I adjusted the idle mix screws and it only got
to about 15 on the gauge. I ran out of time for
now. I hope to get back at it some time this week.

 

I replaced my Thermostat Coil/Spring and the choke is now working perfectly. The truck drives like a dream now. Thanks for all of the help and suggestions.