Stumbles

[cellerdoor]

My 8Nfront mount dis. tractor starts fine moves along good then after a while starts to stumble and wants to stall out even thow I"m getting gas and spark anyone have a clue.Thanks

 

[Bruce (VA)]

It is important for you to tell us if your tractor has a 6 volt or 12 volt electrical system. The troubleshooting is different based upon the configuration of your engine.

It takes three things for an engine to run: spark at the right time, compression, & fuel in the right mixture. For the moment, forget about compression & concentrate on narrowing the problem down to spark or fuel.

" I"m getting gas and spark anyone have a clue."

You DO have a spark or fuel problem & you are not able to find it yet. Simply put........it's not losing compression.

There are three very important tools you always need to have in your N tool box: a 3 inch piece of wire w/ alligator clips on each end, an old spark plug w/ the gap opened to at least 3/16” ( ¼” is better) and a 7/16 box end wrench. (see tip # 50 at the link below) And, you really do need a working ammeter on the tractor; it is a very important diagnostic tool. With these tools, you can quickly narrow down most N problems to spark or fuel.



Next time it stops, check quickly for fuel then spark. When I say quickly, I mean get off the seat, grab the tools & do it right then. Do not wait a minute or two. First, check for fuel. Get a can & put it under the carb. Remove the bolt in the bottom of the carb; as long as the fuel is turned on, you should see gas flowing out of the carb. Let it run for at least 30 seconds. If it’s a dribble, or runs for 5 seconds & stops, or none at all, you have solved half the problem: it’s fuel related. If gas flows well out of the carb & only stops when you turn it off at the sediment bowl, chances are very good it’s not a fuel problem. So, next, turn the key on, crank the engine & look at the ammeter. What is the needle doing? Does it show a constant discharge, no movement at all, or does it move back & forth slightly? Next, get the old plug, ground it to a rust & paint free spot on the engine, turn the key on & crank the engine. If the spark jumps the 3/16” gap, you probably don’t have a spark problem. If it won’t jump the 3/16” gap, you have a spark problem. If the ammeter needle shows a constant discharge, or doesn’t move at all, that also tells you that you have a spark problem. Jump the ignition switch w/ your jumper wire & see what happens. If it runs, you found the problem. If it doesn’t have spark after you jump the ignition switch, post back for more info on further troubleshooting. (and do not forget to turn the ignition switch off; see tip # 38)



If it does not have gas coming out of the carb at a steady stream w/ the bolt out for at least 30 seconds, you have a fuel problem. First, remove the gas cap. Your vent could be clogged & it vacuum locked. If that doesn’t work, tap the carb bowl w/ a hammer handle in case the float is sticking closed. (don’t whack it w/ the head of the hammer; you can crack the bowl). If you still don’t see gas flowing, the N has three fuel screens; one in the brass elbow, one in the top of the sediment bowl & one on the stem of the sediment bowl in the gas tank. Check the screen in the elbow & the screen in the top of the sediment bowl. (don’t worry about the one in the tank) Both probably need to be cleaned. If you have the fuel knob turned on all the way, & 1 gallon or less in the tank, it may be trying to feed off of the reserve inlet which is probably clogged. Only open it 2 full turns. Put at least 2 gallons in the tank. (and do not forget to turn the gas off; see tip # 9)



There are ways to check for spark & fuel that work & ways that don't. For example, having gas to the carb is nice, but having it past the float is what counts! That’s why removing the 7/16” bolt in the bottom of the carb is the way to check for fuel. And, same thing w/ spark at the plugs. Some folks think that checking for spark means pulling a plug wire off & looking for one. Well, it's the distance the spark jumps at the plug that gives you the info you want. It takes about 17kv to jump a 3/16" gap & 22kv to jump ¼” in the open air. Remember, it’s 14psi outside of the engine & about 90psi at a 6:1 compression ratio in the cylinders & compressed air creates electrical resistance, so you really need the 17-22kv to fire the plugs when the engine is running. A store bought plug checker will work better than an old plug because it won’t shock the snot out of you like an old plug might!

Post back after you run these tests as soon as it starts to stumble. If you can't find the source of the problem w/ these tests, then we will move on to some others.

One more question.......

When is the last time you pulled the distributor & set the timing & point gap?
75 Tips

 

[old]

First off check your spark before you start the tractor and make sure it is a blue/white and jump a 1/4 inch gap or more. Then run the tractor till it gives you problems and recheck your spark. I'll almost bet you will find that your spark does not look the same and if the time it takes is say 40-60 minutes then your coil is likely to be going bad and heating up which causes the spark to get weak

 

[Dell (WA)]

cellerdoor........you need to help us help you. Put a "run time" on when yer frontmount starts to stumble. There are 4-common time related stumbles. ........stumble Dell

 

[cellerdoor]

My 6volt stock 8N runs for about 25 minutes and starts to stumble I do have spark and gas flows when I plug the plug on the carb.Thanks

 

[Bruce (VA)]

Does the spark jump 1/4"?

 

[souNdguy]

check spark at moment of death..if spark is good.. carefully check for a vacume ont he fuel tank by loosening hte cap. CAREFULLY.. to prevent splashing.

if no vacume.. open drain at bottom of carb and see if you have fuel flowing into a jar to catch and time it and see stream.

post back

 

[Dell (WA)]

cellerdoor........1-min runtime before stumbles is BAD condenser; NOT yer problem
5-min runtime is CLOGGED intank fuel filter; NOT yer problem
15-min runtime is BAD weak sister ignition switch ($15, cheap) most likely yer problem
1-hr runtime is BAD squarecan ignition coil; NOT yer problem. .......HTH, Dell yer self-appointed sparkie-meister

 

[GB in MT.]

(quoted from post at 13:36:07 11/24/12) My 6volt stock 8N runs for about 25 minutes and starts to stumble I do have spark and gas flows when I plug the plug on the carb.Thanks

b:461a4cff9f][i:461a4cff9f]
Cellerdoor;
You have already got good answers here, and Great questions. AND I'm taking yer word on the fuel and spark!!!!
I hav'nt quite gone whaco....;.just bear with me!!!
Answer these ??'s for me...:
What is yer weather like there, when this occures?....cold?/hot?, high humidity??
Did you let the engine warm up to operating temp, before ya went to working the "N"??????
6 blade fan...???or four blades????
When the engine starts to stutter, have ya noticed ANY wetness on the carb, where it mates to the manifold????

I'm thinking.....Carb icing!!!???

Might be a leaking gasket, at the mating of the carb, and manifold!!
OR, More comon......the air to fuel mix is out of adjustment!!!???
Just a guess!!!!!

You say???????????????????

Gary :?: [/i:461a4cff9f][/b:461a4cff9f]

 

[cellerdoor]

Thank you men for all the great answers this forum is the best.This morning I removed the plug on the botton of carb let it drain into a glass gallon jug over 1/2 was water that settled to the bottom of the gallon darn water in my gas was the problem. Thanks again.