sc still keeps dying

handcrank

Member
I took the carb off and made sure it was clean,blew it out with air hose.Put it back on and removed the plug in the bottom,turned the gas on and let it run a while.Put the plug back in.It started up ran for about one minute.It has a fairbanks morse mag,could the problem be in the mag?This is all new to me.Is there a condenser in the mag that is bad? Thanks for any help, Don.
 
Handcrank,Run it again have a wrench in your hand ,and as soon as it dies pull the plug out of the bottom of the carb and see if you have a good gas flow for say 3 minutes.Catch it in a quart jar so you can check for water and dirt ect.if clean you can dump it back in the tank.Next check for spark as soon as it dies,use a spark tester or an old plug with a 3/16 gap ground the plug in the head or block,or just use a insulated handle screwdriver hooked to the plug wire and hold it 1/4" away from the head or block.You may even disconnect the kill switch wire from the magneto and check for spark,to test the kill switch for being grounded out.If no spark post back.
 
(quoted from post at 13:34:09 05/07/15) I took the carb off and made sure it was clean,blew it out with air hose.Put it back on and removed the plug in the bottom,turned the gas on and let it run a while.Put the plug back in.It started up ran for about one minute.It has a fairbanks morse mag,could the problem be in the mag?This is all new to me.Is there a condenser in the mag that is bad? Thanks for any help, Don.


First did you take the carb apart and clean it, or just blow air from the outside? more often than not it is in the carb or filters. Let me know what carb you have I can email you a manual no charge. I have rebuilt mine several times. Yes the Fairbanks mag has a condenser in it I have 2 OR4B4 Fairbanks magnetos I didn't repair because of the cost of coils and caps. I have had a condenser go bad on a distributor. The symptoms I experienced was It will start seem like its running out of gas and die this happened twice. Then a no start condition this was a brand new condenser I put in the day before. If you have good strong coincident spark, on all your plugs. Id look somewhere else if not could be the coil or the maybe the condenser. Condensers are cheap to replace the coil is not. Also mark the position of the mag so you can put it back were it was. loosen and move it slowly both directions inboard and outboard have someone crank it for you. Also look inside and reset and clean your points and make sure you have no chaffed wires. touching the case. If need be you can get a diagram online or I have some manuals I could send you and some information on how to rebuild it. If you need help let me know. I've rebuilt mine several times but there are lots of different mags that Fairbanks built I MIGHT be able to help you with it if need be. {Need To Know What mag Number you have} I put a Delco p/n 1111411 distributor from a Farmall M or H on mine cost used with the points condenser and cap less than the price of a 2 part Fairbanks cap. I can only help you with what I personally know about. There are experts who have far more knowledge than me.
good luck Byron email [email protected]
 
One way to determine whether the dying is caused by fuel or ignition is to rev it up a little and give it a sniff of ether when it starts to die. If it responds to ether, that mean it is very likely a fuel problem. If no response to the ether, probably an ignition problem.

When my DCs have acted as you describe, it has typically been the fuel flow rate into the carb is too small. After emptying the carb bowl, the flow from the bottom of the carb needs to continue at more than just a strong dribble. There needs to be a continuous steady stream running out the bottom of the carb.
 
(quoted from post at 03:02:57 05/08/15) One way to determine whether the dying is caused by fuel or ignition is to rev it up a little and give it a sniff of ether when it starts to die. If it responds to ether, that mean it is very likely a fuel problem. If no response to the ether, probably an ignition problem.

When my DCs have acted as you describe, it has typically been the fuel flow rate into the carb is too small. After emptying the carb bowl, the flow from the bottom of the carb needs to continue at more than just a strong dribble. There needs to be a continuous steady stream running out the bottom of the carb.

I never thought about ether that's a great Idea.

Byron
 
First thing I want to do is thank all of you guys for your help.Im an older fellow and I don,t always explain things very well.Here we go.I started it up. It ran a short time an died.I quickly opened the plug on the bottom. Gas trickled out and stopped. I pulled the fuel line off the carb and gas flowed in a full stream.I replaced the line and closed the plug on the bottom of the carb.I let it sit for about an hour and tried it again.It started up and for close to an hour befor I shut it down.I started it four times today and it ran fine each time until i shut it down.The only thing that I done different was leaving the gas turned on at the tank all of the time.In the past I always turned the gas off until I decided to start it. I,ll try it again tomarrow and see what happens,again thanks Don
 
(quoted from post at 03:25:08 05/09/15) First thing I want to do is thank all of you guys for your help.Im an older fellow and I don,t always explain things very well.Here we go.I started it up. It ran a short time an died.I quickly opened the plug on the bottom. Gas trickled out and stopped. I pulled the fuel line off the carb and gas flowed in a full stream.I replaced the line and closed the plug on the bottom of the carb.I let it sit for about an hour and tried it again.It started up and for close to an hour befor I shut it down.I started it four times today and it ran fine each time until i shut it down.The only thing that I done different was leaving the gas turned on at the tank all of the time.In the past I always turned the gas off until I decided to start it. I,ll try it again tomarrow and see what happens,again thanks Don

Don did you change the throttle position or choke at all? If it don't leak when you have the tank valve open leave it open. If it leaks you may have to change the way you start it. I have a 1952 SC and I open the throttle a little on mine 2 to 3 inches from all the way forward when I start it this allows more vacuum more gas air mixture. That's about the point when the engine starts to increase RPMs on mine.. If it don't start straight away I just give it a little choke not to much it will flood. Maybe idle passages still a little blocked. I always shut my gas off at the tank as well. You might try replacing the shutoff valve or cleaning it could be gummed up. Just something to try if all else fails.

good luck with it Byron
 
Grew up on sc and then had one for ten years sold it in 2007. Most likely the float in the carb bowl is sticking to varnish or rust when you shut down the fuel flow. Also make sure the pin is proper in the float hinge. An sc will start on very little gas, usually if fuel is restricted they will start and run with little power. Fuel line, fuel bowl, and gas tank obstruction will all cause similar symptoms
 
I,m convinced that the trouble is in the carb.I will take it off and check everything inside again.I think either the float or needle valve or both could be the problem When it,s running I have a good hot spark on all plugs. Wish I had another carb to stick on the old girl. May have to go that way if I can find one.Thanks again, Don.
 
That Zenith carb seems to be sensitive to dirt. I put an inline car filter in the fuel line of my SC many years ago to solve the plugged jet problem. I worked with the sediment bowl over and again to get the screen in there just perfect but a little junk still got through and kept plugging the jet. An inline filter doesn't work in some gravity systems but it works for me on this tractor. If you have junk floating around in the tank that plugs the hole that's another issue. I have junk in the tank of my SC and when it starts to sputter I shut it off, pull the rubber hose off the filter, blow back into the tank through the hose with my mouth (yuck) , put the hose back on and away I go.

Could be a condenser problem too like was mentioned.
 
(quoted from post at 15:04:41 05/11/15) I,m convinced that the trouble is in the carb.I will take it off and check everything inside again.I think either the float or needle valve or both could be the problem When it,s running I have a good hot spark on all plugs. Wish I had another carb to stick on the old girl. May have to go that way if I can find one.Thanks again, Don.

Fixerupper is quite right. I put an in line filter on my SC as well, mine is from auto zone just a cheap white plastic filter with rubber fuel line. Particles of rust can get by the screens and you will get pretty tired of pulling it off to clean it. Important! Can you tell us what you have done or replaced? Did you try ether like Ron suggested? Handcrank its a two way street it would be helpful if you could answer some of the posts with specifics. The questions are meant to help you and eliminate issues. Can you tell us what carb you have? There's a small tag with numbers riveted to the carb.{Mine has a Marvel-Schebler Carbureter and did have a Fairbanks mag}. Did you spray around the carb and manifold to check for leaks. Have you checked compression on it? Have you checked the fit and condition of the gasket on the carb for tears or missing pieces between holes or along the edge? Is the float full of fuel or saturated? Have you set the float IAW (In Accordance With) the manual? Another carb wont fix it if your still getting trash thru the fuel line I can get you the filter number I put on mine if you wish to try it. I think everyone would really like to help you get it running but you need to give us feedback on what you have done so far. Pictures are ALWAYS helpful as well. If you have a son or daughter. grandson or grand daughter, neighbor that can put pics on your computer we can help you from there.
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Lastly It would not hurt to do a tune up change the points and condenser check the timing. I believe most Fairbanks mag points are set at .018 to .020 mine was .020 there's a number on the side of the mag that would help. I still think you have a carb problem probably rust from the tank, but cant rule out anything with out your help.. It would not hurt to do a tune up (AFTER) you clean the carb. One thing at a time.

This is from a ZENITH 9667 but also applies to others not all that fit the SC. This spring clip attaches to the float and the needle valve moving the valve with the float rather then relying on gravity, Is this the carb you have? Is this needle valve setup you have and if so do you have the small spring clip shown in the picture.

This will show the break down on some Zenith carbs Good luck Byron

http://c779252.r52.cf2.rackcdn.com/zenith_61.pdf

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