Dear Ole Mechanic;Ford Tractor

A while back I brought an older N-Series Ford tractor to do shredding and other odd jobs around our small acreage.  It was a lot cheaper than a new one and was doing a great job.  I say "was," as it has developed a problem.  After running for 20 to 30 minutes, it starts losing power and missing like it is running out of gas.  If I pull the choke out a little, it runs better, but still not right.  I cleaned and flushed the fuel system--including the tank--and even had the carburetor rebuilt.  No help.  The last time it acted up, I pulled the fuel line at the carburetor, and there was good fuel flow.  I even tried checking the points in the distributor, but it is hidden up in front of the engine.  It starts right up, as it was converted to an alternator and 12 volts before I got it; it just will not run long enough.  Help!

Needing to Mow

Dear Needing;

Thanks for a good description of your problem.  Yes, I have run into this problem a number of times and can probably help you.  The coil is going bad, and it starts acting up when the ignition coil heats up.  Choking it makes a richer fuel and air mixture which is easier for a weak spark to ignite.  A new coil is available at most tractor supply stores, at many local parts stores and are also available through tractor mail-order catalogs.  They only run about $25 to $30.  Since the coil is going bad, it may have pitted the points.  A small mechanic's inspection mirror is a big help to inspect the points.  It would probably be a good idea to replace the points and condenser, which are also available at the previously mentioned sources.  See, that wasn'tt so bad, was it.

Now for the hard part, which you have already pointed out--getting to the distributor.  The Ford  N-Series service manual says to tilt the hood to gain access, but it really does not help the access to the distributor that much.  What I usually do is:

1.  Disconnect the battery ground connection.

2.  Loosen the alternator so you can get the fan belt out of the way.

3.  Remove the wire from the top of the coil.

4.  Unsnap the wire bale that holds the coil on top of the distributor and lift the coil out.  Do not lose the gasket. 

5. Take the distributor cap loose, but do not remove the spark-plug wires.  Push the cap forward out of the way.

6.  Make note of which direction the rotor is pointing.  DO NOT crank or turn the engine until the distributor is replaced.

7.  Remove the entire distributor from the engine block.  There are two bolts--one on either side of the distributor.

I know it is tight, but removing the distributor is easier than trying to replace the points and condenser down in that inaccessible hole.

With the distributor out and on a work bench, replacing the points and condenser and setting the point gap is very easy.

Reverse the above seven-step procedure to get things back together.  Be sure that the rotor is pointing the direction it was before you removed the it, and that the drive tang is engaged in the slot before tightening the distributor down.  If the tang is not engaged in the slot you will break the distributor housing.  If you are handy with wrenches, the entire procedure can be done in less than two hours.

But you are NOT done.

All to often in the 12 Volt conversion, the original resistor is ignored or left out of the wiring.  Some time back, one of my columns addressed a 6 Volt to 12 Volt conversion for an old pickup.  In it I mentioned that Fords have a ignition resistor in their 6 Volt systems that reduces the 6 Volts to about 4 Volts for the coil.  Your tractor has--or at least had--a resistor in the coil wiring.  If it was ignored or removed when your tractor was converted to 12 Volts, the 12 Volts will fry the coil in short order.  Even if a 12 Volt resistor is used, it will only reduce the Voltage to 6 Volts which will fry the 4 Volt coil too.  It may just take a little longer.  What is needed is a 12 Volt to 4Volt resistor--which is available--or a 12 Volt to 6 Volt resistor AND the original 6 Volt to 4 Volt resistor in series in the wire from the ignition switch to the coil.  What you need to do is look for the original resistor--a coil of thin wire on the back of the dash and--or a white ceramic resistor.  It will be a white ceramic block about inch by inch by 2 inches long with wire connectors on each end.

Which ever is used--a single resistor or the two resistors--you will need from 2.2 to 2.6 Ohms of resistance in the wire that goes to the coil.

If all this wiring and resistor stuff is not your cup of tea, then there is a 12 Volt aftermarket coil available for about the same price as the standard coil.  If you use one of these coils, then make sure that there isn't a resistor in the wire going from the ignition switch to the coil.  This can be easier, as you can tape up the existing wire to the coil and then run a new wire from the switch to the 12 Volt coil.

I hope this gets you mowing.

Herr Professor Nuzanbolts

 PS:  I got a follow up on this one.  The tractor had the two resistors.  The points were cleaned with the help of a small mechanics inspection mirror, and a new coil did fix it.