8n wont start

my 8n acting up its 12v, front dis, gas on on wont start but I give a little starting spray starts up runs good and starts rest of the day next day no start again thanks cdv

When is the last time you changed the plugs, points, condenser, rotor & cap & set the timing?

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 won't start, check for spark then fuel. First, 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

Next, 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.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.

75 Tips

ill check it tomorrow but why dose it start rite up when I spray it thanks Bruce

Because ether is more volatile than gasoline. A weak spark will ignite ether but not gas. Rule out a weak spark and fuel flow issues first.

Is your choke choking?

Obviously following Bruce's advice will get to the root of your cause.

But....

After a night of sitting instead of spraying starter fluid into the carb inlet (where air intake tube is connected to carb)place the palm of your hand over the carb opening and try and starter her up.

What happens?

BTW Bruce I just ordered that same Spark tester off of ebay. Got tired of getting zapped. Seems like i am always in a hurry or loose spark at the wrong times like in 15 degree weather.

(quoted from post at 17:45:59 12/12/14) ill check it tomorrow but why dose it start rite up when I spray it thanks Bruce

Click to expand...

I had the same situation as you describe. I started checking plug wires. When I pulled wires out from the distributor (side model) I found one that the little clip on the end was all black and looked burned. I'm assuming that the wire had pulled out a little and was not making good contact.

I just put on a new plug wire and it fires up fine now. No spray fluid needed. I would say your problem is definitely spark.

"Is your choke choking?"

That's a good thought. Similar hard starting issues can happen
if the little spring is missing from the flapper on the choke plate.
Easy enough to check, but I still wouldn't rule out weak spark.

At this time of year You might also want to check your oil bath air clean for ice.

Kirk

typical ford