Ford 4000 No Spark

[RiverV]

Hi folks, been away from here for a few years.

I have a 1966 Ford 4000, 3-cyl., gas. I am not getting any spark replaced points, condenser and plugs. Still no go. I am wondering if the coil may be bad and what I would need.

With the ignition on I measure 6V at the one primary terminal. (not the one that goes to the dist.) hen I turn the key to start the voltage goes up to over 10V at the terminal.

I am assuming I have a 6V coil and it is switching up to 12V when the starter is engaged. Am I on the right track here? What coil do I need for this tractor?

The tractor was my dads and sat for a few years but was running. I have it home now.

Thanks for any help you can give. Also have a John Deere B that was my dads. That is for another thread... Dave..

 

[RickB]

Your tractor has a 12 volt system with a resistance wire buried in the ignition circuit of the main wiring harness between the key switch and coil. It also has a "bypass starting" wire connecting the start relay to the ignition coil. Both of these wires should be connected to the + primary winding terminal on the ignition coil. When the engine is cranking over on the starter full battery voltage (less the voltage drop caused by the starter current draw) is supplied from the start relay to facilitate starting. When the key is released, the ignition coil is powered by the reduced voltage from the key switch and resistance wire. The correct coil for your tractor is a "straight coil" also referred to as an "unresisted coil" or a "6 volt coil". Even a 6 volt coil has a primary circuit resistance value but it is lower than the resistance value of the style of coil you do not want: a "resisted coil", or a "12 volt coil" or a coil marked as having an internal resistor.

 

[i7win7]

points properly gapped? rotor reinstalled? coil wire to distributor ok? Your voltage readings are correct. good ground connection on coil? when the voltage on primary terminal goes from 6 or 10 volts to 0, the collapse of the magnetic field causes the high voltage spark from coil. use clothespin to hold coil wire close to frame and use jumper wire to ground the distributor terminal to test coil (assuming good ground case connection and points switch ground connection on coil primary)

 

[RiverV]

Your tractor has a 12 volt system with a resistance wire buried in the ignition circuit of the main wiring harness between the key switch and coil. It also has a "bypass starting" wire connecting the start relay to the ignition coil. Both of these wires should be connected to the + primary winding terminal on the ignition coil. When the engine is cranking over on the starter full battery voltage (less the voltage drop caused by the starter current draw) is supplied from the start relay to facilitate starting. When the key is released, the ignition coil is powered by the reduced voltage from the key switch and resistance wire. The correct coil for your tractor is a "straight coil" also referred to as an "unresisted coil" or a "6 volt coil". Even a 6 volt coil has a primary circuit resistance value but it is lower than the resistance value of the style of coil you do not want: a "resisted coil", or a "12 volt coil" or a coil marked as having an internal resistor.

Thanks much Rick. Tomorrow I'm going to check the points again to see if I have them gaped correct. I doubt it is the coil but Can't figure out what else it could be at this point.

I get a little over 10V at the + terminal when the starter is engaged and 6V when the key is on so I do have voltage to the coil. I ordered a 6V coil this afternoon to give it a try.

I grew up working in the fields with this tracto. I would like to get her running again. Dave..

 

[RiverV]

points properly gapped? rotor reinstalled? coil wire to distributor ok? Your voltage readings are correct. good ground connection on coil? when the voltage on primary terminal goes from 6 or 10 volts to 0, the collapse of the magnetic field causes the high voltage spark from coil. use clothespin to hold coil wire close to frame and use jumper wire to ground the distributor terminal to test coil (assuming good ground case connection and points switch ground connection on coil primary)

Thanks, I will give that a try tomorrow. So I should ground the primary terminal that goes to the dist.?

 

[i7win7]

How to Make a Taser (Stun Gun) - YouTube

Found "fun with ignition coils" video. The condenser (capacitor) may be the most important part of circuit. Video gets fun around 2 minute mark

 

[RiverV]

Just wanted to chime back in and let you all know I got the tractor back running. The New Holland dealer ordered me a new set of points and condenser. Replaced the point set and condenser I had put in. Key switch would not engage the starter relay, was iffy before. With some starting fluid in the air intake I jumped the relay and after a few cranks it came back to life.

What a wonderful sound.... Just wanted to say thanks for all the help.

I did find that the connectors going to the B terminals on the voltage regulator were somewhat corroded. Cleaned those up and now the key works as normal. I have a few other electrical issues to deal with yet, fuel gauge not working for one.

I replaced the broken choke cable also. I can see why dad never dealt with that as it took me awhile to get the bad one out.

Tractor sat for a few years without running so to get it back running I replaced: Battery, Starter Relay, Coil, Plugs, Points and Condenser (twice).

Again thanks for the help..... Dave....