Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 06-26-2019, 12:59 PM   #1
DNLs1930
Senior Member
 
DNLs1930's Avatar
 
Join Date: May 2019
Location: Fort Worth side of DFW
Posts: 171
Default Zenith Carb leak

Long post but may help you help me solve this problem.



I have fuel leaking (draining) out of the carburetor afterstart attempts where it does not start. Almost seems like the intake is somehow feeding pressure into the carb.Fuel does not leak out statically only after a start attempt.

OK so the story is after acquiring my family’s 1930 Model Acoupe I did a quick inventory of things it needed and the fuel system was inthe most obvious need due to an inoperative gas gauge, shutoff valve leak andinterior tank rust (sediment bowl needed cleaned) and a firewall to carb fuelline that was chaffed.


I ran the tank dry (changed the gauge with no issues, theshutoff valve was removed to gain access to the tank low point to help in rustremoval. There was plenty of rust to be removed and this task probably needs tobe revisited with a better plan.



I decided to inspect/clean the fuel shutoff valve and endedup replacing it due to deep scratches in the valve body causing it to leak.


The sediment bowl was full of rust and after reading thisforum decided I better check the carburetor bowl; which was full of rustsediment as well.
I replaced the carburetor gaskets (intake, float bowl (mainbody) and the fuel strainer and drain plug)



I replace the fuel line from the firewall to the carb. Putabout two gallons in the tank checked for leaks, then opened up the shutoffvalve. NO LEAKS!!



I then move the car out of the garage in case it caught onfire and tried to start the car.



The car did not start right away which I anticipated and aftera few attempts noticed fuel coming out of the carburetor.




I watched the start attempt after cleaning up and the gas is“draining” out of the carburetor after a start attempt. It almost seems likethe intake is somehow feeding pressure into the carb blowing the fuel out. Fueldoes not leak out statically only after a start attempt.


After a few attempts (cleaning up gas after each attempt)the ca started and it ran fine. Upon shutdown no fuel drained out of the carb.
Restarted and fuel drained each time it did not start.


Nothing on the carb was adjusted or dismantled only gasketschanged.


THOUGHTS?

DNLs1930 is offline   Reply With Quote
Old 06-26-2019, 03:31 PM   #2
Bob C
Senior Member
 
Join Date: May 2010
Location: So Cal
Posts: 8,713
Default Re: Zenith Carb leak

Sound like it's flooded, how long are you choking it??


Bob
Bob C is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 06-26-2019, 03:56 PM   #3
oldforder
Senior Member
 
oldforder's Avatar
 
Join Date: Mar 2013
Location: Columbus Nebraska
Posts: 171
Default Re: Zenith Carb leak

If you are choking it and it doesn't start, the gas will run out the carb.
oldforder is offline   Reply With Quote
Old 06-26-2019, 04:27 PM   #4
Benson
Senior Member
 
Join Date: May 2010
Posts: 2,579
Default Re: Zenith Carb leak

One or two seconds MAX on each choke

Note choke only works when engine is turning.

Do not mean to be insulting but there are many Utubes where they choke when engine is not turning.

return choke to open ... it should start AFTER you release choke and while still cranking.

then retry with another 1 or 2 ... if no start.

If choke more than 1 or 2 seconds at a time it will leak out throat.

Note some carbs start better if throttle is open slightly. One notch or so from when throttle plate first moves.

Note keep this for cold weather:

If engine starts using procedure above and dies after 2 seconds or so:

Open GAV one turn and retry ... if still dies try another 1/2 turn or so.

If 20 or 30 below it might take two turns total on GAV (gas adjustment valve.)

Normal GAV position is 1/4 turn from closed after warm up ... do not force it.

Last edited by Benson; 06-26-2019 at 11:43 PM.
Benson is offline   Reply With Quote
Old 06-26-2019, 05:42 PM   #5
30 Closed Cab PU
Senior Member
 
Join Date: Aug 2018
Posts: 2,332
Default Re: Zenith Carb leak

If you do not have one - There is a pencil style filter that can be added to the inlet of teh fuel shutoff, will keep teh shutoff from failing due to rust/junk getting into teh valve. This why you had deep scratches.


https://www.brattons.com/fuel-tank-filter-screen.html


Once the fuel valve is fixed, you should be able to leave it on overnight and not have any leakage/drippage from the carb. If you do then you have carb issues, perhaps a leaky float valve or the float level is not set correctly.


When the carb leaks and teh float Bowl is overfilling, it leaks into the Air intake, and then through a small weep hole in the bottom of the air intake. Drains down the side of the carb, and usually drips/runs off the bolt head on the bottom of the carb. So if you have a leak, use you pinky finger and feel on the inside bottom of the air intake to check for gas.


The method above (Benson) is the correct way to start. In the 60s and before many cars you full choke using the cable/knob until it started and then backed off on the adjustment.


On the A the full choke is used to prime/force rich fuel mixture into the intake manifold, release the choke and then it shoots into the cylinders. If some partial choke is needed to keep it running the CAV (Choke rod) is twisted for partial choke. This procedure is also used on old tractors except some do not have the GAV adjustment. Continuing to full choke floods them. Most of the time the Motor fires/runs after the 1-2 seconds of full choke, when the choke is removed, again a shot of leaner fuel air pushing the rich mixture into the cylinders.
30 Closed Cab PU is offline   Reply With Quote
Old 06-26-2019, 05:58 PM   #6
Mulletwagon
Senior Member
 
Mulletwagon's Avatar
 
Join Date: Jan 2019
Location: Florida Panhandle
Posts: 585
Default Re: Zenith Carb leak

Sponsored Links (Register now to hide all advertisements)
Leaky inlet valves are something of a common problem in the Zenith carbs. Might change out the valve with a viton needle unit.
Mulletwagon is offline   Reply With Quote
Old 06-26-2019, 06:06 PM   #7
Synchro909
Senior Member
 
Synchro909's Avatar
 
Join Date: Jun 2014
Location: Melbourne, Australia
Posts: 7,472
Default Re: Zenith Carb leak

Quote:
Originally Posted by Mulletwagon View Post
Leaky inlet valves are something of a common problem in the Zenith carbs. Might change out the valve with a viton needle unit.
A leaky float valve will give the same result as having the float level too high. If it is (too high), fuel will leak into the throat of the carb and onto the gound Correctly set, the fiuel level is just short of this happening.
__________________
I'm part of the only ever generation with an analogue childhood and a digital adulthood.
Synchro909 is offline   Reply With Quote
Old 06-26-2019, 06:43 PM   #8
Benson
Senior Member
 
Join Date: May 2010
Posts: 2,579
Default Re: Zenith Carb leak

Most 1930s and later carbs and others had choke pull offs, air bypasses in choke plate and later like QuadraJet, DualJet Automatic chokes and others and auto throttle advance devices and it was possible to choke and crank until they started and not flood it.

Or in auto chokes ... set the choke and crank.

Model A has none of these features.

Last edited by Benson; 06-26-2019 at 07:06 PM.
Benson is offline   Reply With Quote
Old 06-26-2019, 09:30 PM   #9
DNLs1930
Senior Member
 
DNLs1930's Avatar
 
Join Date: May 2019
Location: Fort Worth side of DFW
Posts: 171
Default Re: Zenith Carb leak

Thanks for all the info I will read and reread a few time to try and get a better understanding of what each has said.


Pretty sure I was flooding it by over choking.


Hey Benson no insult taken and please "insult" all you want; I have thick skin and need to learn.


FYI, SORRY but I will not be starting the car at 20 or 30 below ... Just sayin ;-)


30 ClsdCab: I replaced the shutoff valve but fyi I do have a "filter" on the fuel shutoff but it is more of a "standpipe" with stainless steal mesh similar to the one you describe but has a copper tube that extends higher into the fuel. I think it was "made" to prevent increase rust sediment from entering the line. I have the shorter version you refer to but decided to reinstall the one that came off; seems to work good. I do think I will be cleaning this tank sooner than later.

SO to start I should open the GAV a full turn (CCW) then return to closed then approx. 1/4 open
Choke for 1-2 sec while cranking engine.


I did not realize the choke sent a richer fuel schedule I thought it reduced the air to get a "richer" mixture by reducing the air.


Are there any good animations on how these carburetors work?


I will try tomorrow and post me results.


THANKS AGAIN for all the HELP and lack of criticism.
DNLs1930 is offline   Reply With Quote
Old 06-27-2019, 12:16 AM   #10
30 Closed Cab PU
Senior Member
 
Join Date: Aug 2018
Posts: 2,332
Default Re: Zenith Carb leak

Quote:
Originally Posted by DNLs1930 View Post
Thanks for all the info I will read and reread a few time to try and get a better understanding of what each has said.


Pretty sure I was flooding it by over choking.


Hey Benson no insult taken and please "insult" all you want; I have thick skin and need to learn.


FYI, SORRY but I will not be starting the car at 20 or 30 below ... Just sayin ;-)


30 ClsdCab: I replaced the shutoff valve but fyi I do have a "filter" on the fuel shutoff but it is more of a "standpipe" with stainless steal mesh similar to the one you describe but has a copper tube that extends higher into the fuel. I think it was "made" to prevent increase rust sediment from entering the line. - I agree, seems reasonable


I have the shorter version you refer to but decided to reinstall the one that came off; seems to work good. I do think I will be cleaning this tank sooner than later. If you have a gouged fuel shutoff it either got in the valve before the aftermarket screen/filter got put on, or the screen openings are too large. If the small one has a finer screen, might want to use that one.

SO to start I should open the GAV a full turn (CCW) then return to closed then approx. 1/4 open. Choke for 1-2 sec while cranking engine.
See links below, there is a starting procedure. Also you should get a copy of the Model A Users/Instruction manual . Procedure is in there plus tons of other great info
http://www.palmbeachas.com/Model-A-I...ion-Manual.pdf

I did not realize the choke sent a richer fuel schedule I thought it reduced the air to get a "richer" mixture by reducing the air. You are correct, the butterfly valve in the air intake closes, removing air from the mixture making the mixture richer.


Turning the GAV adjust a different needle valve, closes a different valve, clockwise runs leaner, counter clockwise runs richer.


Are there any good animations on how these carburetors work?
Here are a couple of links that should answer your questions on Carbs.


http://www.modela.org/basic_info.html
http://www.modela.org/procedures_full.html
http://www.modela.org/
http://modelabasics.com/Carb/ZenithC...l2011-2007.pdf

I will try tomorrow and post me results.


THANKS AGAIN for all the HELP and lack of criticism.

Most of have at one time been where you are, we are here to help.
30 Closed Cab PU is offline   Reply With Quote
Old 06-27-2019, 12:30 AM   #11
30 Closed Cab PU
Senior Member
 
Join Date: Aug 2018
Posts: 2,332
Default Re: Zenith Carb leak

Here try this link 1st, more basic with animation, good starter info.


http://modelabasics.com/carb%20basics%202.htm
30 Closed Cab PU is offline   Reply With Quote
Old 06-27-2019, 07:17 AM   #12
Keith True
Senior Member
 
Keith True's Avatar
 
Join Date: May 2010
Location: Epping N.H.
Posts: 2,969
Default Re: Zenith Carb leak

Split the carb halves,and look at the bowl vent,where it vents to the atmosphere.It will be in the top half,to one side and just below the float bracket.It is a tiny hole,and if it gets plugged the air can't escape and the float won't rise to shut the valve off.I had a bug crawl in there in a newly done carb sitting on the bench for two days.I would start the car,it would run a little rich,and when I shut it off I would get a rush of gas out the throat. I have a small ultrasonic tank,and for some reason the bugs seem to like the smell of the parts after they have dried off.
Keith True is offline   Reply With Quote
Old 06-27-2019, 08:25 AM   #13
DNLs1930
Senior Member
 
DNLs1930's Avatar
 
Join Date: May 2019
Location: Fort Worth side of DFW
Posts: 171
Default Re: Zenith Carb leak

Quote:
Originally Posted by 30 Closed Cab PU View Post
Here try this link 1st, more basic with animation, good starter info.


http://modelabasics.com/carb%20basics%202.htm


Very nice!
DNLs1930 is offline   Reply With Quote
Old 06-28-2019, 10:07 PM   #14
DNLs1930
Senior Member
 
DNLs1930's Avatar
 
Join Date: May 2019
Location: Fort Worth side of DFW
Posts: 171
Default Re: Zenith Carb leak

Hey all wanted to share my (our) success with the choke and fuel leaking out of the carb.


Car started right up with no issues and ran like a champ!




One of the "techniques" I have read is turning off the fuel and allowing the engine to continue running essentially emptying the carb of gas to prevent fumes or leaks.


If this technique were to be used (it does make sense in a way) any ideas on how long after opening the shutoff valve would the carb have a full bowl and be ready to start?


THANKS for all the HELP!! Love this car and forum.
DNLs1930 is offline   Reply With Quote
Old 06-28-2019, 10:54 PM   #15
30 Closed Cab PU
Senior Member
 
Join Date: Aug 2018
Posts: 2,332
Default Re: Zenith Carb leak

Quote:
Originally Posted by dnls1930 View Post
hey all wanted to share my (our) success with the choke and fuel leaking out of the carb.


Car started right up with no issues and ran like a champ!




one of the "techniques" i have read is turning off the fuel and allowing the engine to continue running essentially emptying the carb of gas to prevent fumes or leaks.



some like to do this, i am not sure why. I do not feel the need and do not have problems not doing this. I think if the fuel system is 100 %, not needed. With a good working fuel valve, leakage would be minimal if an issue with the carb. Especially if you turn the fuel valve off. I sometimes forget to turn the fuel valve off and no leaks, however it is good practice to turn the fuel valve off in case something does happen so you do not end up with a puddle of gas under your car. Once in a great while the float valve will stick open, if you see gas draining under your car, a few taps on the float bowl with a wrench or hammer will usually get the flaot valve to seat and it stops leaking


if this technique were to be used (it does make sense in a way) any ideas on how long after opening the shutoff valve would the carb have a full bowl and be ready to start?



only as long as it take to fill the gas line from the sediment bowl and the carb and fill the float bowl, should only take a few seconds. I guess that the limiting factor is teh flow rate of the float valve.
thanks for all the help!! Love this car and forum.





xxx





30 Closed Cab PU is offline   Reply With Quote
Old 06-28-2019, 10:57 PM   #16
Chuck Sea/Tac
Senior Member
 
Chuck Sea/Tac's Avatar
 
Join Date: May 2010
Location: Between Seattle & Tacoma
Posts: 2,351
Default Re: Zenith Carb leak

No more than 5 seconds
Chuck Sea/Tac is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 05:01 AM.