how does older carb work? mine won't stay running.

canucklehead · May 20, 2013

I took apart and cleaned carb on my '62 IH B414. I was able to clean the jets and got good carb cleaner spray and blew air through them. My problem is fuel flow. I can dump gas in through carb and tractor will run. The moment I stop feeding it fuel, it sputters and dies.

There is a large butterfly valve on top of carb controlled by a choke cable. no problem, that works.

There is a second, smaller butterly valve controlled by the throttle cable. This is where I think my issue is. This valve would not fully open. It has a rod/lever connected to something inside the float bowl. I'm guessing that lever is connected to the accelerator pump (but could be out to lunch on my guess). Whatever that rod connects to is seized. So I banged on what I'm calling the accelerator pump and got it down deeper inside float bowl. Now I can at least see the smaller butterfly valve open and close when I move the throttle cable. But the "accelerator pump" is still not moving and is now stuck in a down position. I suspect it is supposed to slide up and down freely with the rod connected to the valve.

So would this seized part cause me to have no fuel flow? Anywhere I can buy a new float bowl and "accelerator pump" ?

I loosened the fuel line fitting at the carb and cranked engine and fuel seemed to flow well from the fuel pump to the carb.

One other possibility (doubtful)...... when I pulled off the float "needle" flap (it's not a needle, it's a flap), I didn't pay close enough attention to which way it sat. The flap says "top" and I positioned it so "top" was facing up (as in I can read "up" when the flap sits on top of float bowl), so i think I got that part correct. I think when the float raises this flap pushes on the needle to stop gas from overflowing into float bowl (??). Anyways.... possibly i got this upside down or incorrectly installed and needle isn't opening to let fuel in (??).

NormL · May 21, 2013

If you post some pictures of your carb someone on here may be able to guide you. You don't say anything about the carb running over. If you had, that might mean the float was stuck low in the bowl. How about when you open the carb up again. Is there evidence of fuel present? If not, then try tracking down the problem from that angle.

canucklehead · May 21, 2013

thanks NormL. I will remove it and take some pics in the next couple of weeks. I found someone else that seemed to have similar problems. I believe they called it the accelerator pump valve. Not sure if being seized, I'll have to remove it in order for it to run.

If I put the float needle flap in upside down, i think fuel would overfill and leak out. It wasn't doing that. It also wasn't getting enough fuel to run. I couldn't get part of the carb apart (2 slot screws hold the jet assembly in place). I got one to break free and I could tell I'd strip the second screw if i kept working it.

So what's a good product to soak this in for a few days to try and free up some of these seized pieces?

jab-law · May 22, 2013

I actually sounds like you are not getting enough vacuum. It that case, the carburetor itself may not be the problem, but the vacuum may have a leak. Check to make sure that all the vacuum hoses to the carburetor are hooked up, and that they are not cracked. also, you should check the gasket around the base of the carburetor. While the carburetor itself may still be the problem, getting the vacuum leaks issue checked will ensure that you are getting enough air pressure through the carburetor (venturi effect).

canucklehead · May 22, 2013

i didn't notice a single vacuum hose. There is a fuel pump to get fuel there at the banjo bolt.

wondering if the "accelerator pump" off the throttle cable does the same thing as vacuum would do (?)...like pump fuel?

canucklehead · May 23, 2013

I am going to post 8 pics in 2 posts.
The first 2 pics are of the 2 different sides.

notice the rod going into the float bowl on pics 2 & 3 . i think this is for accelerator pump.

pics 4 & 5 are the float bowl. Notice the groove, and one end has an indent/concave, the other side is more convex. so which end is up, and which is down on this float bowl?

canucklehead · May 23, 2013

here are the last 3 pics. this isn't a very clear pic but it should give the idea. This is the flat float flap that gets pushed against the needle. It is sitting on top of the float. I was trying to get a good macro shot of the word "top" on the flap. So "top" is facing up towards me taking a picture. I assume that this is in the correct position. It can be flipped to sit the other way (maybe the word "top" faces the float, and not facing up towards me????)

side view of the float bowl. 2 screws hold a block against the inside of the float bowl (next pic will show this "block" better). The jets are mounted on this block . You can see one screw is getting close to stripped. Can I use an impact driver on this, or will I destroy float bowl? I'd like to remove that block to clean it up better.

okay, lots of info in this pic!! the block has the big brass jet on it. To the left is the accelerator pump valve/plunger. You can see the top is a bit shiny and mangled from me trying to pull it off with needle nose vice grips. Not sure what I can do to free this up/remove/clean it. I smacked it downward into the channel it sits in, so at least the throttle valve will open and close, but this plunger doesn't move. I am soaking the entire float bowl in diesel fuel (recommended by my cousin). i also have solvent but he thought diesel would work better. Any thoughts?

canucklehead · May 23, 2013

this is a Zenith VN carb. i noticed B64 stamped, and I also saw letters that looked like C1836 or C1886.

NELS1 · May 23, 2013

The accelertor ppump has to move freely up and down and on older equipment usually made of leather rather than neoprene .
As the name suggests it pumps ( Squirts ) extra fuel into the carb on acceleration. The float sits at the bottom of the float bowl and allows fuel to fill the bowl assembly until it raises and shuts off the fuel supply by pushing the needle or flap over the hole the fuel comes in. Look inside your toilet to see exactly how the float works. Same principal.

Leejohn · May 23, 2013

canucklehead said:
here are the last 3 pics. this isn't a very clear pic but it should give the idea. This is the flat float flap that gets pushed against the needle. It is sitting on top of the float. I was trying to get a good macro shot of the word "top" on the flap. So "top" is facing up towards me taking a picture. I assume that this is in the correct position. It can be flipped to sit the other way (maybe the word "top" faces the float, and not facing up towards me????)

side view of the float bowl. 2 screws hold a block against the inside of the float bowl (next pic will show this "block" better). The jets are mounted on this block . You can see one screw is getting close to stripped. Can I use an impact driver on this, or will I destroy float bowl? I'd like to remove that block to clean it up better.

okay, lots of info in this pic!! the block has the big brass jet on it. To the left is the accelerator pump valve/plunger. You can see the top is a bit shiny and mangled from me trying to pull it off with needle nose vice grips. Not sure what I can do to free this up/remove/clean it. I smacked it downward into the channel it sits in, so at least the throttle valve will open and close, but this plunger doesn't move. I am soaking the entire float bowl in diesel fuel (recommended by my cousin). i also have solvent but he thought diesel would work better. Any thoughts?

!st pictures isn't clear as you said, to me it looks like the lever that shuts off the needle is up side down. It looks like it could dig into the float.