# 1940 9n won't start please help!!



## Buckshot031989

How it going I've got a 1940 9n tractor that I can't get running. I've checked the spark and it does have a weak spark but it is getting spark. It is getting gas to the carb but not to the cylinders!! All the plugs are dry as can be I can't figure out what it is any advice would be great oh and the compression is around 85 to 90 on all 4 is that ok?


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## tcreeley

When I couldn't get my '48 Farmall Cub to go I used to pour in a little gas into the cylinders through the spark plug hole - replaced the plugs and then hit the starter. When it was cold I always left a magnetic block heater plugged in. Below 32 it wouldn't start with out it. 

I ended up replacing the points on the magneto, distributor cap, the wires, the plugs, and the coil. I'm not that good at thinking it all through- so I do one after the other, I rebuilt the carb as well.

Good luck.


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## ErnieS

First, how long has it been since it ran? How old is the gas?. Try pouring, maybe a tablespoon of gasoline down the carburetor and cranking it. Does it fire at all?
Answer these questions, and someone here can probably help you out.


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## Buckshot031989

I've changed the plugs and wires drained all the old gas out put fresh gas in took carberator off and cleaned it out it's got a new cap and coil it's getting gas to the carberator but not to the cylinder plugs are dry it's been probably 6 months seance it has been ran and the only way he was able to run it was pull starting It.


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## Pipertec

Make sure the coil is grounded good to the frame. also make sure that the wire from the coil to the top of the distributor is good. If the coil and spark wires are old replace them. You should be getting a very hot blue spark. Check the coil input voltage while you are turning the start over to make sure you are getting the proper voltage there while cranking (the battery could be weak too, if the voltage drop is a big one). Any drop in voltage at the coil input will reduce the output voltage of the coil resulting in misfires. If there is no gas getting to the cylinders, there has to be a problem with the carburetor. Either the jet is stopped up, or something of that nature. You don't say anything about choking it? If the battery is fine, try taking the intake hose off the carburator and covering it to simulate choking it and turn it over a little bit....there should be a strong smell of gas at the intake and it should try to fire a bit and run. If it runs for a bit and then shuts down, you have a jet problem.


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## Buckshot031989

The spark is a dull orange


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## tcreeley

My old 48 Farmall cub wouldn't start one day after I did a bunch of work on it. I even towed it with my pickup. It would fire, but wouldn't keep running. I took a break and came back and checked my wires. I had crossed two of them and the firing order was wrong. Put them right and it started up fine.


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## tired-retired

*tired-retired*

All above suggestions are good. One other check would be to make sure there are good connections on all your battery cables. Tight connections are extremely important on a low voltage system. Look for corrosion or anything that would allow for a voltage drop when the load is applied. Testing of the battery might show good, but when you apply a load, full current might not be getting to the coil. No doubt, you've got to get gas to the cylinders. Recheck the carb. and test battery while under load.


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## Pipertec

Dull orange is an indication that output voltage is too low. It should be a blue spark. If you checked the battery connections, input voltage to the coil, coil housing is grounded properly and all that checks out okay, then I would check the coil to distributor wiring and the distributor. It seems to me you are either losing some the the High Voltage to leakage (to ground). That spark should be electric blue! Also make sure your spark gap is right on the plugs and that they are not set too wide. The gas in the cylinder is a good test, but don't overdo the amount you put in or you will drown the plug or cause a situation called "Head Lock" which can damage your piston rods. I am assuming that you have replaced all the fuel in the tank as you said above. That orange fire is the hint. Your plug fire is just not "Hot" enough. Remember, you are dealing with many thousands of volts on the output end of the coil, so any cracks in the wiring, or the distributor will result in a very dramatic loss of voltage to ground.


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## Pipertec

I just noticed that you said the only way you could start it was pulling it off. That brings to my mind low cylinder head compression. Get a gauge and turn it over and check each cylinder to ascertain that you have the correct amount of compression on each cylinder. When you pull it off, you get the engine rpm's up enough to overcome the compression leaks and it will start firing and after it warms up a bit it will continue to run due to the metal expansion in the cylinders increasing the compression ratio. If you plow with it like that, it will most likely bog down once the engine comes under load because of low compression.


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## Buckshot031989

The compression on 1 is 90, 2 85, 3 85, 4 80


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## Buckshot031989

If I got a new batery because I'm preaty sure this one is toasted what should I get as far as crank amp draw what size should I get?


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## Pipertec

as big as you can fit in the tractor is my rule. Tractors sit a lot, and I like a big battery on my diesels. Your is a gasser, but it will benefit from a large battery. Think about it....your sitting there cranking on it, and the battery voltage is dropping incrementally. The hotter the battery and the larger the cranking amps.....the better. I would always used a Deep Cell Battery on farm equipment. I am partial to the Marine type batteries.


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## Pipertec

The Compression numbers you have given are not that low......A new rebuilt engine should see around 125 per cylinder. Your is probably worn down a bit. If one of them was unusually low...say 40 or so, I would think you would need a new head gasket....or something could be crackeds....or a 0 reading would indicate a stuck valve.......But those numbers seem in line with what you would expect from an older engine. I am starting think you problem is your fire is not hot enough. Did you try the teaspoon of gas down the spark plug hole that was suggested by one of the other posters? If so, what happened. What ever you do, don't use any ether on this engine as old as it is.


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## Spartywhite

Yes but why no gas getting to the cylinders?
I have the same issue as the OP.


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