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Zenith 12566 peeing gas out air intake

SeasonedGeek

Registered
I'm sorry if this seems long winded. I'm one who believes the journey is almost as important as the destination.

Circa 1950-something Towmotor 501 forklift I bought off eBay quite possibly 2 decades ago. We don't use it much so it seems like I spend more time fixing it than using it. Has a 4-cy continental motor and until recently it had this carb.

IMG00243.jpg
Sorry for the lousy photo.

Long before I got this thing someone converted from mechanical fuel pump to sub $20 electric. Every 2-3 years I put another sub $20 electric fuel pump on it because that's how long the cheap ones last.

For the past few years, every spring when we wanted to start using it to move seed and chemical around (this is on a family farm) we would end up having to have the forklift repair place take a look at it, pull the carb, rebuild the carb, remount the carb, and hand me a bill for just shy of $700.

This year I was home and not out being an IT consultant when it came time to get it ready. Pulled out the re-purposed headlight switch and the electric fuel pump made no sound. Hit the starter button and engine rolled over so not dead battery. Ordered two different sub $20 fuel pumps on eBay just in case one took a long time to get here. Also bought a check valve so the fuel would quit draining back into the tank causing the pump to sit there dry for months most likely contributing to its failure.

Installed new fuel pump, pulled switch out, nothing happened. Assumed the repurposed headlight switch was bad. Another one was $5 at Autozone and I was going to town anyway. An army of mice had built a city inside the little box housing the switches and gauges. They gave it that "homey smell" by peeing all over too. Headlight switch was rusted and pole broke off when I touched a screw driver to it so not a wasted $5. Replaced that and took out the hack they had splicing power off the backup beeper (which was moved up to disable long before this thing was last painted.) The backup beeper was apparently grounding power because pressing the button made the pump work.

I was busy with the engine choked trying to start then I let up on the starter button for a dozen or so seconds and saw gas peeing from the air filter. I ass-u-me-d the reason the carb needed to be rebuilt each year was the float was bad and when he put the new needles & seats in it masked the problem for the couple of months we use this lift. Did a lot of searching on-line and found a Zenith 12566 is what was supposed to be on it.


Norfar.com only wanted $320 shipped to my door for a new one. This one had a brass T-valve kind of thing that you can see at the back where the one on it had just a cap/plug. I also learned that many cub cadet lawn mowers had Zenith carbs very similar to this. Given all of the jury rigging I've seen on this thing I'm assuming someone scammed a carb off a junk lawnmower at some point. Spent a couple of hours trying to get the nuts started at the top before getting the carb mounted to the under side of the intake. Just not enough room for your fingers.

IMG00230.jpg
Hooked everything back up and pulled the switch out. Pump started pumping. Had to play with the starter switch to get it to engage. By then this brand new carb was peeing out the air filter barrel. Uttered frustrated words. Read the tiny sheet of paper that came with the carb. Twisted the T-valve to what I thought it told me and tried again. Gas again peed out the air intake. Not a dribble, a stream, like most of the pump volume. Uttered more frustrated words. Decided the 5-9 PSI pump might be too much for this carb. Removed it and re-installed the 3-5 PSI pump I had taken off. Pulled out the switch and the same thing happened.

We have never smelled nor seen this thing leak gas before. I'm not certain the T-handle/valve on the back is set correctly, but shouldn't the float raise and seal off the fuel inlet when the bowl is full?

I have done some Web searching before coming to my trusted source (you guys didn't steer me wrong with the Onan generator on my bucket truck). It appears Model A fords have a similar Zenith carb and it is normal for it to pee gas out the air intake if the engine isn't running or is over choked.

http://modelabasics.com/Starting & Driving.htm

It appears old IH Farmalls have a similar carb and they too pee gas out if over choked or the engine is not running.
http://farmallcub.com/phpBB2/viewtopic.php?f=170&t=94624

I've even found comments on yesterdays tractors about similar issues with these carbs and nothing being wrong.
https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=ford&th=427241

Am I chasing a Red Herring here? Has this always been an issue and I've just not noticed it because it used to have a snorkel oil bath air cleaner and I changed it out for a little motorcycle air filter because I was tired of oil getting sucked into the carb, gumming things up?

What is the correct setting/adjustment for that brass T-handle valve in the back. The instructions weren't clear about the 1.5 turns. Do you screw it all the way out then crank it in 1.5 turns or do you screw it all the way in and crank it back out 1.5 turns?

What setting should the idle needle be?
IMG00238.jpg

I know I need to replace the starter switch. I have one on order. The condition of the current one is I have to push the button many times before the starter begins rolling over the engine. Given the size of the mouse nest, and the fact the button was initially stuck when I went to use it (lots of WD-40 got that working) I'm fairly certain a new switch is needed. It shipped today. If the Post Office doesn't get shut down due to Coronavirus, should be here in a few days.

Sorry if this seems like a long winded post, but typing things out in posts or emails is how I think things through. Part of me is starting to believe that once I get the engine rolling over without the choke set, (assuming both valves get adjusted correctly) will make this peeing gas problem go away. Another part of me believes it was too much gas. It does seem to be a bit less gas with the old pump.

Any thoughts you guys and gals have would be appreciated. I need to get this running as seed and chemical will be arriving soon. Well, it will be arriving if they are not impacted by the "shelter in place order" just issued in Illinois.

Thanks,
 

David Hoover

Subscriber
Sounds like a stuck float and gummed up innards from old ethanol gas. I’d start at the fuel tank and take everything off and clean it out.
 

grub54891

Registered
Age
63
Last Subscription Date
06/08/2010
A new carb should not do that. As far as the Needle settings, they won't stop the flow of fuel no matter where they are set. They are for adjusting the mixture.
Start by removing the carb, remove the bowl and make sure it's clean. From there, you can hook a mity vac to the fuel inlet. Turn the carb upside down and pump up the mity vac, it should hold about 5lbs of pressure. The bowl does not have to be on for this test. I test them with bowl off then on to find the issue. If it don't, something it either wrong with the float Needle and seat, or the float is hanging up in there.
 

oldgoat

Email NOT Working
Screw that adjustable main jet in till it seats and then screw out 1.5 turns. and check out adjusting the float level on a zenith carb on youtube
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
DO NOT OVER TIGHTEN THE ADJUSTMENTS! If you do you just junked your new zenith! screw them in until you start to feel resistance and stop! then back out ever how many turns. the 1&1/2 turns out is just a ball park measurment you will have to fine tune it to where it runs best. does this thing have a fuel filter in place? If not GET ONE! a piece of dirt/ trash/ lint between the needle and seat is enough to cause it not to seal and piss gas out just like you are experiencing. Zenith is a damn good carb IMHO. $700 service call you say? DAMN I AM IN THE WRONG BUSINESS!!!!!!!!!
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
also, ditch the extra check valve, the fuel pump should have its own internal check valve.
 

Glenn Ayers

Subscriber
Last Subscription Date
02/18/2019
Most of these old style carbs are only going to want 1 - 1 1/2 lbs of fuel pump pressure.

.
 

SeasonedGeek

Registered
Most of these old style carbs are only going to want 1 - 1 1/2 lbs of fuel pump pressure.
I thought of that, but the other carb ran 3 years with this pump. Really don't want to take a brand new pump off and apart to work on float though. There are 2 fuel filters in-line. One old style (and new) silver barrel and a tiny screw onto the pump finer filter. I'm beginning to wonder if the thing got bounced around too much during shipping.

Thanks,
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
One thing to remember, this is a updraft carb. so any fuel that dont get sucked upward into the engine is going to come out at the lowest point. Its hard to diagnose over the internet, I would suggest going back and just power up the fuel pump without trying to crank it and see what happens. If nothing runs out it sounds like it is a flooding condition, if gas runs out without cranking you are going to need to pull the carb and see what is going on with the float and the needle. float could have a pinhole letting it well not float and not shutting the fuel supply off when it gets full.
 

David Hoover

Subscriber
How about hooking up a small starting tank to the carb, hang it higher than the carb and see if it still floods. If it dosent you’ll know it’s the pump. If it does keep flooding it will be your float valve
 

Pete Deets

Subscriber
Last Subscription Date
01/01/2020
This is very much like the updraft carb on my 2N Ford tractor. If you crank too long with the choke full on it will pee gas out as described. It is a gravity feed with about 18 inches of drop so there is very little fuel supply pressure in that system..........PD
 
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