Zenith Carb on '69 Ford 2000-Float setting?

[Bob_Young]

Well, raising the float didn't help. Raised it a good eighth of an inch. Still need to have the choke halfway out to have it run smoothly. The float seemed high to begin with....a good sixteenth less than your quarter inch benchmark, Chris.

Also tried the propane torch trick to no effect. I was still suspicious of the vacuum advance line to the distributor, so disconnected that and put my finger over the fitting at the manifold end. Had no effect, finger in place or not.

There appears to an acceleration pump built into the carburetor that's activated by a sudden drop in manifold vacuum. There's a spring loaded rubber diaphragm beneath the carb. bowl that forms the bottom side of a chamber that's connected to a nozzle that discharges upstream of the venturi. The discharge nozzle was clogged; I cleaned it out and can blow Gun Scrubber through it in the discharge direction, but cannot see through it or push a wire through it. It may have a ball check valve in it's base.

I have not figured out how fuel gets into the chamber controlled by the diaphragm. It did have some nasty old gasoline in it when I took it apart and I had to clean up everything in there, but the only passage from the carb. bowl I've found, ends in a small chamber that is blocked off by a brass screw. There's another mysterious brass device in the top of the chamber that I can't describe...gas may get in that way. However fuel gets in, it can't be just a simple passage....the discharge nozzle is below the level of fuel in the bowl.

There appears to be two jets of about the same size in series between the bowl and the main discharge nozzle....one at the bowl exit and another a bit further along angling upward toward the discharge nozzle. Didn't write down their sizes, will do so next time I'm in there. I believe fuel for the idle circuit is taken off somewhere between the two jets....this is something I have to confirm. If not, I don't see the purpose of having two jets in series.

Used my new gaskets when it went together this time. If anything it's slightly worse now when the choke's all the way in. It seems to stagger or bog when the governor opens the throttle to recover from the RPM drop.

After this latest go-round, I too began to wonder whether this thing needs a twist drill run through the main jet (whichever one it is). Could be that this is sort of a generic replacement carburetor and needs a bit of setup for the engine it's put on.

Sorry this is so long and thanks again for the suggestions.
Bob

 

[Soundguy]

If you have the 09D03 zenith on that unit.. ( 65-74 oem )

Then i have an exploded diagram for you.. and a small parts list.. Unfortunately most parts are NLS.

PM me with your fax number and I'd be glad to fax on my nickle to anywhere in the CONUS.

Soundguy

Soundguy

 

[Soundguy]

I wouldn't suggest boring out the main jet... that carb should be sufficient for the 158 ci 3 cyl.

My only guess would be is if the main and idle ject can be swapped. On some MS carbs you can do that.. etc.

soundguy

 

[rgc53]

When i installed the zenith carb on my Ford 3000 the
engine ran very well , idled at 650 rpm , you should
consider taking the carb. apart and soaking the pieces
in carb cleaner!
Also check the length of the rod between the govenor
and carb , the rod length is adjustable and critical ,
if the rod is too short it will cause the engine to run at
high idle and the govenor to surge , the it manuel will
give you directions , there are a number of steps to
adjust all linkages!

RGC

 

[Bob_Young]

Good tip, RGC. I'll look into the governor rod adjustment. I wouldn't have thought of that. Thanks. I think this thing is due for the carb cleaner bath as well.

Chris, this carb is not the OEM Zenith AFAIK. It's a replacement; Part No. 13913. It's among that list of carbs & parts that you linked me to at ytmag. There, the number is at the very end of one of the carb descriptions. On the carb itself, there's a little metal tag bearing the number. Could be it's similar though. There's no fax here, but I'll PM you a number at work if this doesn't show signs of turning around. Thanks for the offer.
Bob

 

[Bob_Young]

Update for anyone interested:
Disconnected the governor yesterday to try running it while manipulating the throttle by hand. Did this to take the governor variable out of the equation. It would not hold a stable RPM unless the choke was halfway out....same as it was doing with governor in the loop. With choke full in, throttle had to be operated much the same as what the governor had done to keep it going. Yet, when operating with choke all the way in (and RPM going up and down), there was a very strong smell of partially burned gas in the exhaust....smelled like it was running rich, or the fuel wasn't being completely burned.

I'm beginning to suspect that a partly clogged air bleed is preventing proper fuel atomization. With choke out, the air pressure balance may be altered enough to pull more more air through the bleed or turbulence from the partly closed choke plate may help atomization or.....?

Anyway, next time in the float's getting lowered back to what it was. Then the carb's getting a good bath and a checkout of every passage.

Although interesting, this underlines why I find new equipment much more appealing in my declining years. The time spent solving little mysteries in the old stuff is better spent doing something productive.
Bob

 

[Soundguy]

Choke usually indicates fuel obstruction.. or vacume leak... in this case.. I'm betting on fuel obstruction.. the dip/cleaning will be good for it.

Soundguy

 

[Bob_Young]

Update on this:
Soaked the carb in a bucket of cleaner for a couple of days, put in a new gasket set and lowered the float back to where it was. It runs OK now.

On disassembly, I noticed that one or two tiny holes in the side of the fuel delivery nozzle were plugged. I think these holes admit bleed air into the nozzle fuel stream to help atomization. The holes in the upper section of the nozzle were open, but those in the bottom section were not. Don't know if that's what caused this problem, but it was the only issue I could see.

Now it's on to the rim rot problem. New rims and rubber are next.

Thanks for the help and the ideas.
Bob

 

[Soundguy]

Good job.

soundguy

 

[shealray]

Try 1/4"

I've mainly messed with the MS carbs.. but do have a zenith on my 850.. and it may well be the same as your 3 cyls..

I use a 1/4 drill bit as a gauge... works great.. Also.. flaot setting is not as fatally specific as you might think... as long as you get it close enough that it lets gas in the bowl when empty, and does shut the needle off before gas overflows into the main chamber past the venturi.. then it should be fine..

Check for holes or that it doesn't hang up onthe sides.. etc..

Soundguy

I also have a 850 with a zenith carb, but after running 2 hours the tractor stops and I hit it on the side of the carb tractor runs. My guess the float is sticking. I am new to carb rebuilds so is there a easy way to fix a sicking float. Maybe carb cleaner ? I do not know how to identify the Zenith carb for a kit. Also could the glass bowl cause this issue. Thank you for your help.