Farmall 404

M

Morris farm

Active member
I've been working on a farmall 404 tractor. It has been converted to12 volt negative ground. My problem it had a dead battery so we jumped it an it started. Used it to do some work then put it in the shop to put a new battery in it. Put new battery in and replaced the positive cable when I attached it to the started selanoid I didn't notice the cable end was touching the R terminal on the selanoid so the oil and amp light was flashing with the key off. Fixed the problem and now it won't start. Checked the voltage to the coil positive side and getting 12.50 volts. It does have a voltage resistor on the coil and that has voltage to it. Very little voltage to the distributor points, it does have a condenser inside the distributor. It is not getting spark from the coil. What could be wrong with it. Thanks Brian
 
Check to see if the points arc when they open and close when the engine is cranking with the ignition is on. No spark--no start. The points have to fire for the coil to work. That's just the way inductive current works. JMHO Stan
 
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Morris farm said:
No spark when points open and close. Wonder if i shorted something out? Condenser?
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If you have current to the post on the distributor where the power from the coil connects, you either have a bad set of points or a faulty ground at the points. When you get the points to fire as I described then check the output (center, tower) at the coil to ground, It's about 18K volts so it should jump a gap about 1/4 inch with a good crisp blue arc. (I fought that one once and had a bad coil on the high voltage output.) Once you get that point verified check the spark at each plug. If no spark then there's probably a problem with the rotor or distributor cap. Stan
 
Morris farm said:
No power to the post on the distributor and that wire is from the negative post on the coil
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If you are measuring this with the points closed, there will be no voltage at that post. It is directly grounded through the points. The points are usually closed when the engine is stopped. If you turn the engine until the points open, you should measure full battery voltage. This all assumes the ignition is turned on.
 
No voltage to the points with key on and points open. It was running good until I changed the battery and the positive cable. Is it possible I shorted something out when the positive cable was touching the R post on the starter selanoid. Could it be the condenser? Thinking of changing the points and condenser but I don't know what set to get because it has been converted to 12 volt.
 
Morris farm said:
No voltage to the points with key on and points open. It was running good until I changed the battery and the positive cable. Is it possible I shorted something out when the positive cable was touching the R post on the starter selanoid. Could it be the condenser? Thinking of changing the points and condenser but I don't know what set to get because it has been converted to 12 volt.
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Disconnect the wire from the coil at the distributor post and back-track from there toward the battery and see where the power stops. Could be the ignition switch or any wiring connection/junction. If you want to test the engine starting/running, connect a jumper wire from the battery hot post to the input side of the coil and the engine should start if there are no problems from the coil going forward. As for the points and condenser I don't think it will matter if your coil is a 12v internal resistor type. JMHO Stan
 
I have 12 volts to the positive side of the coil but nothing going to the points with the points open. Is it possible the condenser is bad. What condenser should I use on a 12 volt converted from 6 volt
 
Morris farm said:
I have 12 volts to the positive side of the coil but nothing going to the points with the points open. Is it possible the condenser is bad. What condenser should I use on a 12 volt converted from 6 volt
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If "nothing going to the points" means no voltage at the neg side of the coil, then the coil is bad. The + and - terminals on the coil is just a continuous winding inside the coil case. I would swap the coil for a known good one and try that first. JMHO Stan
 
You need to physically disconnect the wire from the coil to the distributor as Stan said in post #8. Then check for voltage at the coil terminal that you disconnected. Without disconnecting the wire, a zero voltage could mean a short to ground in the distributor. Zero voltage with it disconnected says a bad coil. The only way a bad condenser could cause what you have reported is if there is a dead short inside the condenser. Possible, but it hardly ever happens.
 
staninlowerAL said:
If "nothing going to the points" means no voltage at the neg side of the coil, then the coil is bad. The + and - terminals on the coil is just a continuous winding inside the coil case. I would swap the coil for a known good one and try that first. JMHO Stan
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I tried another coil and it starts. It was a 6 volt coil from a farmall cub. The 404 has a voltage resistor mounted on the coil bracket. It was 6 volt but converted to 12 volt should I get a new 6 volt coil and use the voltage resistor or should I get a 12 volt coil with internally resisted.
 
Your choice. It will work either way. I would probably get the 12-volt coil and reduce the number of components and connections.
 
Morris farm said:
I tried another coil and it starts. It was a 6 volt coil from a farmall cub. The 404 has a voltage resistor mounted on the coil bracket. It was 6 volt but converted to 12 volt should I get a new 6 volt coil and use the voltage resistor or should I get a 12 volt coil with internally resisted.
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It's your choice, if you want to use the 6v coil install a resistor between the battery feed and the input to the coil so you get 6v input to the coil. A 6v coil with a 12v input won't last very long. My personal preference is to use a 12v coil with internal resistor and you can remove the existing resistor as it's no longer needed. (Less things to cause problems.) With that setup the coil output is then correct for the distributor and you won't burn the points. IF you use a 12v coil/no internal resistor you will need an inline resistor before the distributor to keep from burning the points. JMHO Stan
EDIT: Sorry I didn't intend to restate Jim Becker's response. I failed to see that he had posted the info.
 
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Morris farm said:
If I use a 12 volt coil with internal resistor What do I do with the 2 wires going to the external voltage resistor?
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You will probably have to trace them to see where they are connected. If the old coil you removed was a 6v then expect to find that the source is ignition switch and the path is switch to resistor to coil to distributor. If that's the case you can connect the two wires together that were removed from the old resistor and thus feed the new coil 12v input from the ignition switch. Stan
 
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staninlowerAL said:
EDIT: Sorry I didn't intend to restate Jim Becker's response. I failed to see that he had posted the info.
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At least we gave the same answer. :)

When you remove the ballast resistor, you also remove the wire that went from it to the coil. You take the other wire that connected to the resistor and connect it directly to the coil, where the discarded wire had been,
 
staninlowerAL said:
You will probably have to trace them to see where they are connected. If the old coil you removed was a 6v then expect to find that the source is ignition switch and the path is switch to resistor to coil to distributor. If that's the case you can connect the two wires together that were removed from the old resistor and thus feed the new coil 12v input from the ignition switch. Stan
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This is photos of the coil, 2 white wires, one goes into the harness and one to the external resistor other side of resistor is black wire that also goes into harness. 2 white wires connect to the positive side of the coil. red wire is negative on coil goes to the distributor. Owner said It's always been a 12-volt system, sorry for the wrong information. The photos are the setup it has now. So what do I do with the white and black wire? If I go with the internal resistor.
 

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Morris farm said:
This is photos of the coil, 2 white wires, one goes into the harness and one to the external resistor other side of resistor is black wire that also goes into harness. 2 white wires connect to the positive side of the coil. red wire is negative on coil goes to the distributor. Owner said It's always been a 12-volt system, sorry for the wrong information. The photos are the setup it has now. So what do I do with the white and black wire? If I go with the internal resistor.
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Looking at the pics and your explanation leads me to the following speculation:
1. White wire from harness is a feed/supply probably from the ignition switch to the coil and resistor. Disconnect it at the coil and resistor to see if it has voltage controlled by the switch. Reconnect at the coil and leave the resistor not connected
2. If this is true, the feed from the switch supplies the coil and the resistor.
3. You said that the red (neg) on the coil goes to the distributor. You can verify this by disconnecting the wire at the distributor post and check that voltage is supplied to the distributor through the coil by the off/on action of the ignition switch.
4. With the resistor feed disconnected start the engine (or at least check that the points are arcing as they open and close).
5. If the engine starts and runs with the resistor disconnected it's very likely that the resistor is connected to something other than the ignition . JMHO Stan
 
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