The Stovebolt Site Forums The Shop Area The Electrical Bay 6 volt coil question

Okay, I got the engine to turnover very well. Now I need it to fire. I have new plugs and plug wires, distributer looks good. I have two wires running from the coil. One goes from the + side of the coil to the distributer, the other is spliced into a heavy wire (running from the starter post to the firewall) and goes to the negetive side of the coil. I wasnt getting any spark from the plugs, it is then I noticed the wires are very worn and barely hanging on. I want to replace them. So the question is 2 fold:

1. What gauge wire should I use to replace these coil wires?

2. What is the purpose of the wire being spliced into the wire that comes from the starter? Did the PO try to bypass the ignition?

Thanks in advance for your help guys!

Forgot to add, that I have a 1951 3100 with a 1957 235 engine running a 6 volt system.

Purney,

The coil wiring you indicate is backwards for a NEG ground system, which a Chevrolet is. If this were a GMC of that vintage, it would make sense.

If this is a NEG ground Chevrolet, Positive (+) side of the coil normally goes to the key switch to get power when you turn the key on and stomp the starter. The negative (-) side goes to the distributor.

14 gauge or 16 gauge would work fine for these wires. You mention a wire running from a 'starter post on the firewall'. I'm not sure what this is. This doesn't sound like anything one would find on a unmolested Stovebolt.

I think more information is needed. It sounds like something might have been swapped or modified in some way.

Stuart

You are right! I had that mixed up but it is - to distributer and + to starter.

To clarify my post the positive wire goes to a heavy gauge wire coming off the starter post. That heavy gauge wire goes into the firewall I assume to the ignition? I havnt checked that yet. My question is, should that Positive wire be spliced into this wire coming from the starter? It looks very unstable.

Are you sure it's spliced to the starter post wire? It is more likely just in the same loom and running parallel to the switch with the big wire going to the ammeter and the coil wire going to the ignition switch, otherwise you wouldn't be able to turn the engine off without pulling the coil wire and your points would be welded together.

Purney,

The heavy wire you are describing (10 gauge) that comes from the starter should go into the cab and attach to the positive side of the ammeter. The coil wire (+) shouldn't and probably isn't spliced into that big wire! It might appear it is spliced into the heavy wire, but is actually taped along side of it in the loom and goes into the cab to be attached to the key switch.

It would not function if it were spliced into the heavy wire...actually it would work, for a couple of hours!

Stuart

It had black tape wrapped around it, I'll have to double check that but it really looked spliced! Thanks Baldy

That is how you hotwire one of these old girls. Your ignition switch would not allow you to shut the engine down; you would need to pull the wire off of the coil. (As was already mentioned)

As was also already mentioned, it will work, but your engine could need some new ignition parts when you were done if you weren't careful.

Odd thing to note, My starter has three wires attached to the post, the Batter cable, a heavy gauge wire that looks to be the 10 gauge and then a smaller one that the coil wire is spliced to. All three wires attach to the bolt via with only the nut holding them on. Is there supposed to be some other way of holding this stuff on?

I think your wiring is right for a 12V system (you say yours is 6V though) and the wire coming off the starter solenoid is the resistor bypass wire. Since you don't have a resistor it seems to me the wire going to the starter solenoid is useless. I would take that wire off the solenoid and eliminate it leaving you with just the one wire from your ignition switch to the + side of the coil.

Purney,

Any wire attached to that nut on the starter switch will have power all the time...not switched! The large cable from the battery proper is obviously the conduit to supply power TO the starter to make it spin.

The other large wire, 10 gauge or so, is the supply for all electrical items on the truck AND the path the power takes back to the battery from the charging system. This bolt is sort of the master connection for all things big and powerful.

I don't think there is a third wire normally attached to this point. It doesn't mean there can't be though. The wire to the positive (+) side of the coil MUST be switched. No wire running from that bolt on the starter is switched. They do make a starter switch that has a small bypass terminal on the side that is involved with the ignition system, but it isn't a big bruiser, and your rig isn't configured to use it.

Stuart

All great stuff, thanks all. I will be double checking everything tonight and will let you know what I find. Thank god for this site!

I just checked the wiring diagram for this truck it does show a third wire to the starter, but it also shows the coil going to something I am not sure what! anyone want to take a peek and tell me what the think??

http://chevy.tocmp.com/1948_51truckshop/51ctsm1202.htm

Purney,

I think you might be looking at a different application. If you look closely, you will see two examples of the wiring. The one with the 'starter switch' is for a different style truck. The diagram you want is the one showing the positive coming from the ignition switch.

Don't confuse yourself. If you have a voltage tester, just find out if the + side of the coil turns ON and OFF with the key switch. It most likely will, and how it does this will be addressed later, after you get it running.

Stuart

Purney,

From reading your previous posts I know that your truck has a stomp starter. Because your starter engages manually, the only means to turn the ignition on and off is with the key switch. If you leave the key OFF, you can still turn the engine over, but it won't start. It is possible that some previous owner tagged several lines on to the starter switch...it's real convenient. That does not change the fact the the only way to power the coil so the truck will start, and to kill that power so the truck will shut off, is with some type of switch, the key switch. Does this make sense.

Stuart

Yes, Its starting to sink into my thick skull! I will be checking with my voltage tester tonight and hopefully get this thing running without blowing myself up. I will post my results!!! Thanks guys.

Okay, it is not spliced into a line, you guys are once again correct, it is a seperate line running inside the loom. The third wire goes to the horn! and to my surprise actually works. The horn is mounted on the firewall above the starter. I am not getting any power to the coil using a tester it appears, even with the switch on. I am thinking of running a new line from the coil to the ignition. Is the 14 gauge wire okay? Is this a good idea?

Before replacing wires, check to see if you have six volts to the switch and if you do, make sure the switch transfers that voltage to the coil terminal of the switch.

Purney,

Are you familiar with the meter you are using. You have seen it work on a live circuit and are sure your coil wire test was valid.

Stuart

I installed a new coil, but still am not getting any spark. The tester is new and I have used it and it does work. No juice on positive side of the coil either. To check the switch baldy are you referring to the ignition? and if so what is that procedure. I have feeling that it may be the problem, although all other power is getting to lights horn etc.... My truck is in your hands, what is my next step? thanks guys.

Purney,

I hope I'm not dominating this thread! You are backtracking, trying to find where you have power and where and why it stops. The key switch gets power from the ammeter and switches it to the coil and (I think) the fuel gauge. The horn and lights are not switched so they won't be a good indicator of a defective switch.

If you turn the key on and off, do you see the fuel gauge move? If you do, it means the key is getting power..it also means the set of contacts is getting power. If I'm correct, the coil is on that same set of contacts and this would mean there is a wire problem from switch to coil.

The 'moving fuel gauge' test isn't 100% reliable. Sometimes the fuel gauge is defunct. If you are agile and flexible, crawling under the dash with a good trouble light and actually testing each key switch contact is the next step.

There will be a terminal that has power all the time, and at least one more that have power when the key is turned on. Enough for now!

Stuart

Just a passing thought. Doesn't the key switch in these old rigs have a uncommon ON position! Make sure you are actually turning the switch to ON.

Stuart

Fuel gauge works when I turn the key on. it has to be then from the switch to the coil. I am halfway agile and once was flexible, so under the dash I go!!

What do you mean by uncommen position?

Thanks Stuart.

Purney,

Crawl away! Again, I'm not sure on this, but I think the ignition wire AND power wire for the fuel gauge are connected to the same terminal on the key switch. Your test with the wiggling fuel gauge shows you that the key switch IS working. That leaves the wire from key switch to coil as the suspect #1. Before I ripped out wires, I would test it again at the coil, making sure I had the key in the position that made the fuel gauge work!

In regards to the key switch position, I thought ON was a position most folks would automatically assume was OFF...maybe in the vertical plane! I don't remember.

Stuart

holy cow, I got to thinking about your "uncommem position" so I re tested the coil in what I thought was the off position, Bingo! 6 volts at the + side of the coil. Now it has to be either points, condenser or cap right? I rechecked to see if the plugs would fire and they dont. I wasted a whole day on this. Thank god for your comment about uncommen positions

Any insights into what I should next?

Purney,

Good job! Although the cap and condenser could be causing problems, my bet would be with the points. They must be adjusted properly to allow the coil to function. I'm not positive but I think the setting is around .019 or so. Take a look and see what develops.

Stuart

I had a guy over tonight that used to work on the Radars for the navy ships. We used my multimeter and tested everything under the sun. What doesnt make sense is that even though we are getting power to the coil we do not get a spark from the coil to the distributer. We pulled the wire and could not get a spark by grounding with a screw driver. Would this then indicate that I must have a bad condenser? Just seems odd that even though we have power to the coil we cant get a spark out of the coil.

Purney,

Condensers do fail and they can cause the problem you seem to have. The easiest test would be to attach your multimeter to the - side of the coil and ground. This would be in the DC volts mode. As you crank the engine over with the key on, the meter should alternate between 6 volts or so and zero volts. If it does this, the points are opening and closing, and the condenser is fine.

The points are the 'switch' for the coil. With the key on and the points closed, the coil windings will saturate. When the points open, the primary winding collapses across the secondary and creates the high voltage...ZAP! If you pull the cap and turn the motor with the fan until the points are closed, then turn the key ON and open the points with a screwdriver, you should be able to get the high tension coil wire to ZAP a gap to a good ground...is this how you tried to do it? I think this is how it works!

Stuart

Awesome info atomarc. We just put the screw driver in the high tension coil wire and grounded it, turned the key on and turned the motor over with the foot stomp starter, no spark. That should have caused the points to open and close and the screw driver to zap. I will give your technique a try.
Also on the side of the coil bracket their is a condensor of some sort. It attaches to the + side of the coil. What is this and could it be the cause of my trouble?

Thanks so much atomarc for all your help!

Purney,

There are anti-static capacitors that are attached in various places in the system, the + side of the coil being one of them. They help reduce electrical noise in the radio...they look just like a ignition condenser. This probably isn't a part of your problem, but you can disconnect it if it bugs you.

Have you pulled the distributor cap and actually inspected the points yet. Your screwdriver test should have gotten results, although you will want to hold the screwdriver 'near' the ground to create a gap for the voltage to fire across. It's pretty easy to just pull the coil wire out of the cap and hold it near the engine block and wait for the zzzzap!

Stuart

have not done the points thing yet but did do the coil wire from the cap. That is what is perplexing, the coil has 6 volts to it but isnt producing a zap from the coil to the distributer. And the coil is new!

Purney,

My guess is that the coil is fine but the test procedure isn't. If you are determined to prove the coil before getting into the distributor itself, you can use the - wire as the 'faux points'. With the key on you should be able to make the coil fire by alternately touching this - wire to ground and then removing it. Remember, don't ground the high tension coil wire, hold it a little off ground so the spark has a chance to build up and make the leap of faith...or, just hold on to that wire with your hand.

Stuart

Success! I put in the new condensor and got no spark, then I put in new points and still no spark! I had my 8 year old daughther stomping the floor starter for me. I went in the house totally frustrated. Then, I felt in my pocket and and pulled out the new rotor cap. Stupid me, I forgot to put it back on after putting the points and and gapping them. I went back out put it on, had my wife turn the motor over and wham! spark! I nearly crapped my pants. Put some gas in the carb, and it came to life for a few seconds. This weekend I will bypass the gas tank and get it running for real.

I had my mind made up it had to be the new coil and turns out all along to be exactly what you told me it was, $3.69 cent points. I tried to overthink it! Now it makes sense, as you said the points are the switch for the coil and when I pulled them and looked at them, they were shot and obvously not switching. Thanks so much for all your help everyone, especially you atomarc. I am one happy bolter!