1949 Ford 8N Tractor Won't Start

Number_35

Number_35

Joined
Jul 7, 2014
Messages
5,169
Location
Winnipeg MB CA
A friend in another province has bought a rural property complete with a 1949 Ford 8N tractor.

He hasn't got the tractor running yet, and doesn't know when it last ran.

Some details:

- 4-cylinder

- gasoline (rather than diesel)

- front-mount distributor

- oil-bath air filter

- gravity-feed fuel delivery (no fuel pump)

He bought and installed a 12 V conversion kit, and a new or rebuilt carburetor.

The engine turns over well, but doesn't fire.

Fuel tank is clean, and the gasoline is fresh.

He had the plugs out, but attached to the plug wires, and grounded by sitting on the valve cover. When cranked, there's a fairly weak orange spark at the plugs.

He has new plugs on order at NAPA.

I've suggested:

- Check the resistance of the plug wires. (Would the wires on something this old be carbon-filled to suppress radio noise, or straight liw- impedance conductors?)

- Check the timing. (No idea on the spec, but TDC (0°) should allow it to start.)

- Check the point gap and dwell angle. (No spec, but 60° should be close.)

- Check to ensure there's no blockage in the long pipe from the oil-bath air filter down to the carburetor.

- Change the cap and rotor.

I wonder if there's any issue with the ignition's primary side now being 12 V rather than 6 V?

So many possible things - I wish I was closer so I could help.

All thoughts on this appreciated!
 
The spark is too weak. On these "N"'s, an ignition system in good shape should produce a blue spark capable of jumping a 1/4 inch gap. A good battery is a must on these. Most likely the points are tarnished. You should replace the points, condenser, rotor and cap. The wires generally are not resistive type which should be avoided.. Many times after a long period of inactivity, you can just run some emory cloth on the point contacts and a piece of card stock afterwards will bring it back to life. Point gap is .015 in. I store my 9N with the points closed and they will last a very long time. On a front mount distributor, timing is done with the distributor off the engine and is tricky to do. I suggest doing a search online to get the procedure. Long ago, I bought a jig that mounts to the back of the distributor to hold everything in place and makes the job much easier. When reinstalling the distributor, don't force it on. It should fall into place once the tangs on the distributor engage the cam. If you try to force it on with the bolts , it will break the mounting ears and likely shear the tangs off when the engine is turned over.

Finally, these tractors perform best with Champion H-12 spark plugs gapped at .025 in.

. Remove the air pipe from the carb and try using some starting fluid to get it going then reattach. Clean the glass fuel filter bowl and make sure the screen is clear.
 
Last edited:
Thanks, all - these replies are very helpful. I've sent a link to the discussion to my friend.

I thought of one more - can the timing be changed by rotating the distributor, or is it fixed?
 
IMG_20240225_071325.jpg

IMG_20240225_071349.jpg

IMG_20240225_071358.jpg

IMG_20240225_071418.jpg

IMG_20240225_071428.jpg
 
My dad always said if it was cloudy outside the 8n's wouldn't start. They are very fussy with distributor caps. I believe it's most likely a spark or ignition issue which Lubener stated. My big brother and I put tons of miles on those old 8n tractors. We hauled bales, manure, sprayed weeds and mowed with those tractors. We also cultivated, plowed, dragged and used a blade on the back for blading my dads lot and driveway. You name it, we did it with a Ford 8n. My dad would buy them and fix them up and sell them. We would strip the paint off of them with zip strip and my dad would spray them and they looked like new again. Many good memories of those tractors.
 
Sometimes when points are bad you can simply take a striker off of a matchbook and sand the points, then reset them. This wears a way at the good metal on the surface of the points even more but if they're bad that's already gone. Then if the points were the problem it'll run for a while but the points won't last anywhere near as long as our new set of points.

Those old Auto Transformer coil ignition systems usually had a capacitor that could go bad also. And of course the auto Transformer coil can go bad. Also, clean up any grease or anything around the top of the coil. You don't want an easy path to bypassing the high voltage to ground anywhere in the system like on the top of the coil or the top of the distributor cap. Those should all be clean. Rubbing alcohol on a rag would be a good product to get rid of the oil and then let it dry very well. Be sure to clean the inside of the distributor cap very well also.

And look for cracks once you have it cleaned up. If you have a crack in the distributor cap or the top of the coil that is a great place for enough material to get into to short out the ignition system.

Sometimes, if there's enough moisture in the oil that's in the crankcase it can come up into the distributor and cause problems. And the one about running for 30 ft sounds like oil in the crankcase with way too much moisture could be one of the culprits. Run it for 30 ft, boil off enough moisture that it gets up into the distributor and short out of the spark. Let it sit long enough that the moisture in the distributor is gone. Fire it up and repeat. And the fact that it ran good when it was cold when it was purchased would also be another clue because if the oil is cold and the engine is cold then it takes a lot more heating up of things before you get to the point where the oil is throwing off enough moisture to short out the distributor cap. I could even see it running for a significant amount of time to get things warm enough before it becomes a problem and then requiring shorter intervals to repeat the problem because things are still warmer than they were on the first startup.

You don't have to get the oil in the crankcase hot enough that it is the source of oil with moisture burning off. There's plenty enough oil being slung on the hot parts like the bottoms of Pistons and cylinder walls.

If you're wondering how moisture gets into the oil the answer is that the atmospheric pressure changes throughout the day. When the atmospheric pressure becomes lower some air leave the crankcase, when the atmospheric pressure becomes higher some air enters the crankcase. And air contains moisture. And if the surfaces that it contacts are cold enough some of that moisture will condense out into water droplets that will then run down into the oil. This is probably made worse by the fact that most days during the daytime the temperatures warmer and during the night the temperature is cooler. If new air has entered during the day when it's warm it probably is also capable of holding more moisture than it could at night. And of course when it gets colder at night some of that moisture could condense out of the air. Repeat this everyday for a few months and you could end up with enough moisture in the oil that it does cause the problem.

Some expensive systems use a desiccant that absorbs moisture out of the air for the breather for the crankcase so that the air that is allowed to go into the crankcase has had moisture removed from it. And in those systems the descant has to be replaced on a regular basis. But that's the difference subject.

Number_35, if I solved your friend's problem, somebody owes me a couple of cold beers.
 
Last edited:
Number_35 said:
Thanks, all - these replies are very helpful. I've sent a link to the discussion to my friend.

I thought of one more - can the timing be changed by rotating the distributor, or is it fixed?
Click to expand...
Rotating the whole distributor cannot be achieved, it is fixed.. Timing is set by the moving of the plate inside the distributor which has the points and condenser mounted to it. There is a large headed screw on the side of the disttributor which locks it down. Like I stated before, you have to remove the distributor to actually set the timing correctly. If you try it with the engine running, you likely will lose your hand thanks to the fan.
 
I had a 8n. Coil was bad. Spark looked fair but no start. New coil strong blue spark....runs.

Also those engines flood easily and the spark plugs get soaked. Remove plugs and dry with blow torch.

My two cents.
 
I didn’t see a ballast resistor in line with the coil. It may be getting hot and cutting out if it still has a 6v coil on it. Other than that, make sure you have clean points, a good condenser, and the rotor is clean. I’m somewhat familiar with these distributors because I had a ‘34 Ford truck with a flathead. Close to the same type of distributors.
 
The owner sent me a scan of the owner's manual for a 1948 model.

Firing order: 1-2-4-3

Point gap: 0.015"

Spark plug gap: 0.025 - 0.028"
 
Weak yellow sparks will not fire the engine. The reason for weak yellow sparks is almost always the coil. Replacement coils are readily available and any 8N owner needs to keep at least one spare on hand. The 12 volt conversion involves either an additional resistor in series with the coil wire, or a coil made for 12 volts. Running 12v directly to a 6v coil will burn it out and is also hard on the points.
 
You must log in or register to reply here.

Similar threads

A
PSA- Dry cylinders = very low compression and no start
Replies
5
Views
3K
tnt_motorsports
J
  • Locked
2007 Ford Five Hundred - shudder/stutter/hesitation only at certain RPM & load
Replies
5
Views
2K
michaelluscher
T
09 Mini Cooper S...I hate this thing...won't start
2 3
Replies
46
Views
4K
terry274
dogememe
02 Honda Accord 2.3L ~280K Miles, distributor failed, still won't start after replacing it.
Replies
19
Views
5K
dishdude
JHZR2
John Deere JX75
2
Replies
31
Views
3K
gman2304
Back
Top