8N keeps dying

DriverChad

New User
Hey Guys,
Hope someone can help. I'm at wits end.
I have a 1949 8N with a front mount distributor. I rewired it year before last and everything looks fine wiring wise. Last week I had a charging problem and replaced the alternator (12 volt system) and it seems to be charging fine now. My problem now is that my tractor runs fine for a while under load ( finishing mower) but then just shuts down like someone turned the key off, sometimes it will fire back up and sometimes it acts like the battery is dead. But the battery reads 12.6 volts. Thank in advance for any help.
 
" I rewired it year "

What resistors are you using? You must use the OEM ballast resistor; are you using any other resistor? 6v or 12v coil?

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

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, a spark checker w/ an adjustable gap (* see below) 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 (** see below) 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, hook up your spark checker, turn the key on & crank the engine. If the spark jumps the 1/4” gap, you probably don’t have a spark problem. If it won’t jump the ¼” 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 (in the picture) will work better than an old plug because it won’t shock the snot out of you like an old plug might!

Post back with results or more questions.



*If you don’t own a spark checker w/ an adjustable gap, buy one. In the meantime, an old spark plug w/ the gap opened to at least ¼” will work. Ground it to a rust & paint free spot on the engine turn the key on & look for a spark.

** On most gas engines, you would check for spark first. But, the N gas tank has a pin-hole size vent that easily clogs, causing vacuum lock. By the time you check for spark on a hot engine, the vacuum lock will dissipate w/ the engine off
75 Tips
 
Bad ignition switch will cause one to just die but should not cause it to not spin over since the ignition switch and the start circuit are independent of each other. So likely to have a poor/loose connection some place which cause it to doe and then act like a dead battery
 
After struggling with a faulty switch on my Jubilee, I put a small red clearance light near the key, and wired it to get power on the same terminal that feeds power to the coil. Ensures that that there is power going to the coil during diagnostics.
 
Acting like dead battery?

What aren't you telling us? Is this key to start or thumb button.

If key to start, I'd investigate power feed to and the key.

If thumb button and sometimes acts dead, check bat cables and terminal ends and ground.
 
Thanks for the help guys, had to replace the alternator again, voltage regulator went out in it. I am getting plenty of fuel, so that's not the issue. It's getting close to bed time and will do some more checks in the morning. I'll keep you posted on the results. Thanks again.
 
Found the problem. Was the points. The gap had closed up to where there was only about .007 space between them. got them gapped at .015 now and she's runnin good. Thank you all. Chad
 

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