slimbobaggins

So I rebuilt my stock carb using Provience's guide and a couple others.

The issue I'm having now is that the fast idle cam isn't engaging when the choke is cold, and I don't honestly see any mechanism that would cause it to.

This is taken, looking at the linkage side of the carb. As you can see on the right hand side, the choke plate is closed because the carb is cold (obviously since it's in my dining room):



This picture is me holding the throttle wide open, and you can see that despite the choke being closed all the way, the fast idle cam doesn't kick down to where it would be engaged (circled in red):



As shown before, the choke is closed all the way, so the linkage attached to it is pulled "up" all the way, but the lever attached to the same linkage (and to the fast idle cam) doesn't push the cam nearly far down enough to engage it, and it's not done via gravity. The spring behind the cam wants to do the opposite, wants to disengage the cam, so that's not it.

Here's a pic of when I let the throttle go, of course you can see that it didn't engage the fast idle cam:



And here's a pic of the cam engaged by me pushing it by hand (for visual reference):



Anyone have any suggestions as to what I've done wrong? The linkage is free moving and not bound up.

This is keeping my truck from running, any suggestions (aside from throwing the carb away and going to a Weber) are greatly appreciated. I've found posts from others that have had this issue, and none were resolved.

-Jim

slimbobaggins

Full disclosure: I definitely have this thing reassembled the way it came apart, but it didn't run right to begin with, so it doesn't mean someone else didn't screw it up before the truck fell into my hands.

slow-mo

What I'm not seeing in your pictures is the linkage "arm" being pushed against the Fast Idle Cam via the spring.




The bottom arrow is the spring, and the top arrow is the "arm" that forces the Fast Idle Cam to rotate into position.

Check to see if yours is this way and report back.

slimbobaggins

Thank you for the response.

After I posted this thread, I figured that out. I reassembled it the way it was when I took it apart (i took tons of pictures for reference), which was with the linkage arm in the "hole" in the idle cam, rather than above it. When I got the truck, it wasn't running, and the carb had obviously been molested, so whomever had it before me obviously didn't know what they were doing.

After I swapped it around to look like the picture you posted, I put it back on the truck and was able to get it to fire up, but wasn't sure that what I did was "correct." You picture confirms that.

Thanks again!

-Jim

slow-mo

Yep, the linkages are the hardest part of rebuilding the stock carb; making sure it goes back correctly.

83danimal

Old thread, new question. 83 pickup rebuilt motor and carb. I verified my linkage is correct and lubed it, fast idle cam works as described. Question, when cold out (50 n below) on first cold start is it normal for engine to slowly rise to fast idle speed as it warms, or should it jump to 2600 rpm right away? Everything seems to function and kicks down to idle when warm enough. it seems to corrulate w condensation burning off out of exhaust. No coolant loss, runs great, checked for vac leaks w propane torch.

thanx, dan

83danimal

Thanx