runs poorly after 5 minutes, leaving tomorrow

ratface

Member
About 2 weeks ago I was mowing with my 1949 8N, front mount 12 volt. Plugs and wires all look good. No fouled plugs or bad wires. Mowed for about 45 min. and just made it back to the barn before it died. Tractor started to surge and act as if it wanted to die. I began to think it was the coil but after sitting for about 20 min. it started right up and this time it took about 20 min and same issue, surging and running poorly. It runs awful up a hill with the brush hog on, can't believe I made it back again. Now it's down to about five min. If it sits for 15 min I can bush hog a steep 1/8 of a mile incline with no problem. If I try it a second time , then surging and running poorly wanting to die out. Thinking it was a distributor issue I replaced points, rotor, cap, condenser, and coil. Parts are from Napa, good set of Echrin points with the jig setup. I also brought along a new ballast resistor. I changed that out after test running after the tune up. No change in problem. Tractor now runs great for five min and then it barely limps it's way back home with surging and almost conking out. Let it sit 15 min and everything is fine again. This is a remote weekend place and so I have to bring in everything thing I think it can be. I've got a push starter switch which I was going to try tomorrow. I don't have a gasket though. Since the switch has only one wire going to it how do you jump across it, do you disconnect the one wire and then jump across the on/off toggle switch contacts? I'm starting to think it's time to look at fuel? I've checked flow out of the carb when cold not running, the stream is steady and strong out the bottom carb drain. I have cleaned the sediment bowl screen. I have not checked fuel flow immediately following problem. What would you do next? Got tomorrow only to figure it out.
 
Loosen or remove your gas cap and try it.
That may be all it needs. It's gravity fed, needs to let air in.

If that doesn't work then by all means check you fuel flow when
it fails. Prep for that by taking the plug out of the bottom of the
carb while cold so you know you can get it out quickly when you
need to. Run it until it acts up, pull the plug and check the flow
through the carb. Have the right wrench and a clear container
with you to catch the fuel. Check the fuel for dirt/water.

The pushbutton starter switch, if original, all you need to do
to "jump" it is connect the little wire to ground. If you don't
have pretty paint a screwdriver touched to the top of the trans
cover and then leaned against the little terminal will do it.

So will a jumper wire from the grounded post of your battery
to that terminal or to the small terminal on the solenoid.
Of course either of those will bypass your neutral safety, so
be ready for that.
 
Ratface just a thought someone reminded me the other day what we would do with old carburetor engines. running poorly we would spray starter fluid in carb if it runs better carburation if not ignition spark or a stuck valve maybe broken valve spring. Id spray ether in the intake to check. Spray around the carb and manifold be careful you don't need much.
I remember as a young man I would just loosen the wing nut for the air filter and pour a little gas around it to get em started (not good) One Day Id pulled off on a steep embankment truck was running weird shut the truck off If I remember right It had a gas tank behind the seat very little gas well all the gas was to the opposite side of were the fuel feed line was for the engine mounted fuel pump. It just was not getting gas. So with my infinite wisdom at 19 years old I just took my gas can loosened the wing nut and poured a little extra gas on top the filter cover just to get me off the embankment and on level ground. Don't ever do that It finally caught up with me the truck backfired and caught fire, I panicked like most young folks would to put it out I pulled off the top of the filter (bad Idea) allowed more air in and threw gas on top the engine burnet a few wires up till I smothered it with my jacket (1 ruined jacket) lesson learned. Here's another at the ripe old age of 13 my brother in-law asked me to get him a little gas I don't remember what for . Well I found a Styrofoam cup poured some gas in and started over to give it to him and well before I got even close the cup started to disintegrate actually it melted away boy was I surprised!
Anyone else ever do something that dumb?

Sorry about the long story hope this somehow helps

Byron
 
Gas cap would be my guess. The original cap is non vented. The vent in top of the tank gets plugged.

Two weeks ago a friend was having a problem with his 51 8n. He said it ran poorly every time he turned right. The longer he mowed the worse it got. I went to look at it. The first thing I heard when I got out of his pickup was a hissing noise. The noise was coming from his gas tank. I opened the cap slowly and carefully. The gas in the 8n looked like it was boiling. We drilled a 3/32 hole in his gas cap. Sent him back out to mow. It ran fine. I ordered him a vented gas cap.
 
There are two schools of thought when it comes to getting a non-running tractor to start. One way is to just start replacing every part you can get to until it starts or you run out of money. The other way is to take a step-by-step approach to solving the problem, working from most likely to least likely. The trick to fixing these tractors (or trouble shooting any piece of equipment) is to be systematic about it. You need to isolate the problem step by step and work from most likely to least likely.

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
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75 Tips
 
I started trying to start the tractor this morning. Would not fire to save my life. It always started just ran poorly. Well I used up the battery trying to get it started, had several close calls where it almost started. While the battery was charging I drained the gas tank to clean the filter inside the tank. I noticed that I get a slow flow with the sediment bowl valve out two full turns but it improves considerably if it is all the way out on reserve. I also pulled the elbow filter and of course cleaned the sediment bowl filter. None of the filters really looked like they needed cleaning. I also changed out the starter push button switch. Was easier than I thought it would be and you really have to get in there to begin to describe it. I had two locking tabs holding my nut which was 1 1/16 if anyone needs to know. Got the tractor started near 4 pm and by then the rain had come so no real chance to test it under load with the brushhog. Is it possible my top sediment bowl opening was clogged and my carb was starving for fuel and does the reserve position give access to the whole tank of gas. Hoping to test it tomorrow if the rains allow.
 
The reserve position does give access to all of the gas.
And any rust/dirt/etc that may be in a 65+ year old tank.
 

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