Low Voltage To One Side Of Coil

[SlowMaintenance]

Hey guys, need your advice. First let's give some background so everyone can be up to speed. Bike has a PMA, Pamco, E advancer and the red andrews coil. The bike runs on a capacitor but this evening I had it hooked to a battery for timing purposes. All of the discussion below is with a battery hooked up.

The bike is wired according to this diagram with the exception that there is an e-advancer between the ignition and the coil and there is no kill switch there, and there is no neutral light. That slot is empty on my fuse block.

I had just replaced a breaker cover oil seal so I had to reset the timing.

Put the timing plate in the closest spot to where it was before and hooked up the battery. Battery had good voltage 13V but I plugged it into a charger at the same time it was plugged into the bike so I could be sure I was getting consistent voltage. Coil read 12.5 volts at both sides.

Started kicking and it wouldn't start. Realized I left one of the plug wires off (oops) so I plugged it back in and still nothing. Figured maybe that messed something up so I opened up my wiring box and sure enough the 7.5amp fuse was blown. I replaced it with a new fuse. There's a light that comes on in the block when the fuse is blown and the light went off when the new fuse went in. Good sign.

Went to start it again, still nothing. Pulled the plugs, pretty black. No bueno. Grounded plug to engine and kicked, yellow spark. Not the usual good blue kind. Also no bueno. Alas, I didn't have another set of plugs so I put them back in and went to check coil voltage, one side still reading 12.5v, this is the side where the green wire from the e advancer runs straight to the coil (its the orange wire in the diagram above). The other wire is the red wire which splits into two with one end going to the fuse block and the other end going to the other side of the coil. This one was now reading only .5v at the coil. I tested the voltage at the fuse block terminal and it's getting 12.5V. So the issue must be between the fuse block terminal and the coil. Which leaves only that splice joint and the wires themselves.

It was late, I was tired, and I was done for the night but glad I was able to narrow down WHERE the problem was. What I don't understand is WHY. The wires were soldered and shrink wrapped at the joint, this exact same wire has run the bike before. Why the sudden change?

Next steps wise, I have three ideas that I need your advice on.

1. Try another 7.5amp fuse and see if the problem persists.
2. Recreate the splice with a new wire (I'm getting dangerously close to the e advancer housing and running out of wire so I don't want to do this again if I can avoid it)
3. Change the wiring setup to run the red wire from the e advancer straight into the fuse block, and the empty slot in the fuse block to the coil (eliminating the 2-1 splice). Idk if this will work though as the two terminals might not actually connect to each other like that.

What are your thoughts? I desperately want to finish this bike so I can ride it to the chopoff, and I'm losing time quickly.

Thank you for your help

 

[retiredgentleman]

I suspect you may have damaged the ignition coil, when you kicked the engine over, while the plug wire was not connected. This is especially likely if you have one of those super high voltage coils such as the #17-6810. Your coil put out high voltage with no place to go, so the high voltage winding may have arced through the insulation. The Pamco itself may also be damaged. Blowing the 7.5 amp fuse indicates excessive current flow occurred, because normal Pamco current is less than 1 amp.

You certainly should inspect the splice and it's wiring, looking for anything that could have caused a short circuit to ground. Use your VOM to measure resistance of the ignition coil windings. There should be very high resistance (infinity) from either winding to its iron core.

 

[SlowMaintenance]

I should have put this link in the original post, sorry about that. This is the coil I have
http://www.jpcycles.com/product/380...e=&network=g&gclid=CIrMu7nfgdUCFUxYDQodsuUHMw

I'll check resistance on the coil and see what it reads. I'll google the process for testing the PAMCO as well.

That being said, I am getting spark when I kick the engine. Doesn't that indicate that the PAMCO is working because it's technically firing?

 

[retiredgentleman]

Yes, you did say you were seeing a yellow spark. That is a good sign that the Pamco is still working. A yellow spark, being a weak spark, points toward the coil only producing a low voltage.
That Andrews coil, being "high performance", likely produces a very high voltage. It may have burnt a hole through the insulation on the high voltage winding.

 

[SlowMaintenance]

Forgive me because I'm not too well-versed when it comes to coils. When you say it may have burn a hole through the winding, that just means the coil is toast right?

You don't replace anything to fix that I'm assuming.

On a separate but related note, if this coil IS toast, is there another coil that is recommended for this setup? I never really liked the look of this coil to be honest, and also dislike the color.

 

[retiredgentleman]

I can't say for sure that your coil has failed. I recommend you measure the resistance of the primary, and the secondary windings. Also measure the resistance from each winding to the iron core. The only problem is that the low voltage used, when on OHMS, is not a good test to detect if the insulation has been burnt through. It might detect it and it might not. A device called a megger is used to test for the strength of insulation, where high voltage is involved. Most people don't have a megger handy.
If the coil previously had a good strong blue spark, and now its a weak yellow, well that indicates the coil is toast.

There are many,many dozens of coils that will work with a Pamco. I use an Accel #140403S (non CDI) 3.3 ohm coil, but they are expensive. Everyone on this site will have a favorite coil they like.
Best to do your own research.......................try "pamco ignition coil" in the Search box in the upper right corner.
Pamco will work with any coil that has a primary of 2.5 to 4.5 ohms IIRC.

 

[SlowMaintenance]

Alright guys, I've got some news to share on this. Went back over last night to work on the bike and I did get her running again, so I don't believe the coil is fried. She ran several times with the choke on, enough for me to get the timing close to where it needs to be.

The rest of the issue is carb related so I'll make another thread for discussion on that.

In the meantime though, one issue does persist, and I'll need some of your guidance to help me determine the problem. The low voltage issue flared back up. It ran and it got battery voltage to both sides when I started working on it, then later I was doing some carb troubleshooting and I couldn't get it started when low and behold, same issue to the same side of the coil. Reads good, kick it a few times, now it reads low.

Here's where I need your guidance. I found this explanation for coil testing on the PAMCO site


Testing the coil:

1. Using the lowest scale on the meter, measure the resistance between the primary terminals with the wires removed. Should read from 2.5 to 4.5 Ohms.
2. Using the highest scale on the meter, measure between one of the primary terminals and the center core of the coil. Should be infinite resistance. (open)
3. Measure between one of the primary terminals and one of the plug wire terminals. Should be infinite resistance. (open circuit)
4. Measure between one of the plug wire terminals and the core of the coil. Should be infinite resistance (open circuit)
5. Measure from one plug terminal to the other. Should be 15,000 to 20,000 Ohms

This is the coil I'm working with

What I'm confused about is the terminology in the test procedure. I see 3 main components to test. Primary terminal, center core and plug wire terminals. On my coil, there are only two exposed metal items. The ones I run my ignition wires to, and the ones my spark plugs go to. I'm assuming this means I have only primary terminals and plug wire terminals.

Testing the coil, I get 4.2 ohms across the primary terminals and 18,000 ohms between plug wire terminals. (I should say, my voltmeter setting is "2,000" and it reads 9 so I'm guessing that means 18,000)

Am I testing this correctly?

 

[mrtwowheel]

Fill in the blanks......Where are you measuring voltage at the coil? By low voltage, are you meaning "weak spark"?

 

[SlowMaintenance]

Good question. I'm measuring voltage with the key in the on position supplying power to the coil. Negative electrode on the frame ground, positive side on the nut holding the wire onto the coil. (The small brass part sticking out from the coil in the pic above) The reading is the same whether I touch it to the nut or the terminal the nut threads onto.

When I first started working on the bike they both read about 12.5V. After some kicking one side drops to .09V, other side still reads 12.5V.

Maybe my wire is losing voltage. But now that I think about it, it can't be the wire. Because that wire is the only one which is bringing power to the coil. The side of the coil which is reading 12.5V is the one with the green PAMCO wire running to it which wouldn't be supplying any power. This just got more confusing lol

 

[retiredgentleman]

I would not be concerned about seeing battery voltage on one side of the primary coil, and near 0 volts on the other side. That is just showing that there is current flow through the coil and its associated voltage drop (ohms law). When testing , don't leave power on for very long or you can over heat the coil.

This is the testing prodedure from Pamcopete's web site.

Testing the PAMCO with E-Advancer
1. Use a voltmeter and check for battery voltage on the red wire with the key and kill switch are turned on.
2. The dual output coil has to have both spark plug wires connected to a spark plug at all times.
3. To test for spark, connect one of the spark plug wires to a spark plug that is grounded to the engine.

To test for spark without having to turn the engine over, do this procedure:

1. Remove the advancer cap on the right side.
2. This will allow you to spin the rotor to produce a spark without having to turn the engine over.
3. Connect one of the spark plug wires to a spark plug that is grounded to the engine, but not installed in the engine.
4. Make sure that the other spark plug wire is connected to a spark plug in the engine.
5. Turn on the ignition switch and the kill switch.
6. Spin the rotor while looking at the gap in the spark plug for a spark.
7. Turn off the kill switch and the ignition switch.

 

[SlowMaintenance]

Ahh, ok, so it's not necessarily bad if it reads lower voltage at one side then. That's what was getting me confused. I've already tested for spark which I am getting and the engine did run yesterday so it's definitely working in some capacity. Was just worried when I saw the low voltage reading that there was some other problem with it.

It is strange through that when I started working on the bike it read battery voltage at both sides. Is that maybe because the voltage drop doesn't occur until you kick it through a few times and "wake it up" so to speak?

 

[retiredgentleman]

Yes, the Pamco E-advancer design is set up such that the engine must make one full revolution before current is switched to flow through the coil primary.

 

[SlowMaintenance]

You're a lifesaver, thank you for confirming this. Now I can stop stressing about my coil and focus on stressing about my carb hahah

 

[XSLeo]

Just for reference, battery voltage flows to one side of the coil primary. This happens with most any ignition, points, TCI, Pamco. As the engine turns over your ignition grounds the other side of the coil primary. Points close, TCI, Pamco, turns on a transistor. This allows current flow through the coil, Building a magnetic field around the coil secondary. As the engine turns further the ignition ungrounds the coil, this causes the magnetic field the collapse, creating a very high voltage in the secondary of the coil. This voltage can reach in excess of 20,000 volts in a stock coil, in some performance coils possibly 100,000 volts.
This high voltage is what causes the spark.
On points, if you test voltage on the coil when points are open, both sides will read battery voltage. When the points close, the positive side may still show battery voltage, but the points side will show no voltage. The points are ground., Ground to ground will read no voltage.
On a TCI or Pamco they use transistors instead of points and even in the off position there is still a bit of leakage across the transistor. This shows up as a low voltage reading.
Hope this helps you better understand ignitions.
Leo

 

[SlowMaintenance]

It definitely does. Thank you for explaining that.

From here, the issue is to determine what's preventing the bike from starting. It could be that the plugs are too fouled up from the float being set incorrectly which is keeping it from running decently. Maybe I can clean them up and see if it makes a difference.