Check the obvious, or the faulty application of Occam's Razor

[Administrator]

10.5 volts seems awfully low. Not my area of expertise (don't ask which ones are), but that doesn't seem right.

Bill

[Bratina]

With that kind of voltage (very close to the numbers I run on my engine) you probably do not need to run resistance spark plugs. You may be ok while the plug is new but later the problem could come back. Try using a non resistive plug. Edit: don't know if this has ben discussed, but you should know what your dwell reading is.

I didn't really know I was I guess that's what the R in the plug name stands for... Which plugs do you run? Admin suggested these voltages are low. Should I be looking to change anything else?

[hanleyclifford]

10.5 volts seems awfully low. Not my area of expertise (don't ask which ones are), but that doesn't seem right.

Bill

The Atomic 4 will run on as little as 9 volts. I have tested this personally and know it to be fact.

[hanleyclifford]

I didn't really know I was I guess that's what the R in the plug name stands for... Which plugs do you run? Admin suggested these voltages are low. Should I be looking to change anything else?

I run both 306 and 308, no longer available so far as I know - but I don't change plugs very often. I believe J8C was once the specification but don't be bound by that. Try to run the coldest plug that doesn't foul, then go one range hotter. One thing you do need, especially with points, is a dwell meter, available for less than $20 at most auto boutiques.

[roadnsky]

...Admin suggested these voltages are low. Should I be looking to change anything else?

Bratina-
I'd like to be certain...
Do you have a resistor ahead of your coil?
I'd like to be SURE your voltage at the coil + is accounting for any upstream resistor.

[hanleyclifford]

Bratina-
I'd like to be certain...
Do you have a resistor ahead of your coil?
I'd like to be SURE your voltage at the coil + is accounting for any upstream resistor.

If there is no resistor ahead of that coil, there is indeed another problem.

[Bratina]

I run both 306 and 308, no longer available so far as I know - but I don't change plugs very often. I believe J8C was once the specification but don't be bound by that. Try to run the coldest plug that doesn't foul, then go one range hotter. One thing you do need, especially with points, is a dwell meter, available for less than $20 at most auto boutiques.

Dwell meter is on the shopping list. I'll check gap next time too, should have done it today when I took the cap off.

[Bratina]

If there is no resistor ahead of that coil, there is indeed another problem.

As far as I know or can see, there isn't a resistor in the circuit. What problem does that voltage point to?

[hanleyclifford]

As far as I know or can see, there isn't a resistor in the circuit. What problem does that voltage point to?

Typically an alternator will put out around 14 volts of which around 13 volts would be making to coil+ after going thru wires and switches etc. Since that is too much for the coil the practice is to put resistors just ahead of coil+ to bring down to 12 volts or lower. There is a formula available using Ohm's Law used by some members, but if you are below 12 volts you should be OK. Your problem seems to be that your voltage is already down there without resistors which means your alternator is not putting out enough voltage or some other problem exists in the wiring. Maybe the next step is to check voltage at Alt+ (large output terminal).

[hanleyclifford]

Dwell meter is on the shopping list. I'll check gap next time too, should have done it today when I took the cap off.

In a new distributor specified point gap should yield specified dwell, but since the lobes are worn on our old distributors this is no longer the case. Dwell is the important specification, not gap; and you will find that correct dwell will land you at a gap setting well below specification - which is OK.

[Dave Neptune]

Bratina, is there a ceramic piece with wiring mounted to the bracket with the coil? With points you could well still have the original "ballast resistor" still in the loop. Can you shoot and post a pic?

The 10.5~10.9 voltage is fine for the ignition but if it is actually your operating voltage it could be an issue.

Look for the big original equipment resistor or even a small one mounted near the coil. The ignition wire from the keyswitch should hook directly to the positive side of the coil, what you need to see is if that wire (purple I think) hooks to something else first then to the coil. It is very common to lower voltages on point systems to make the points last longer.

Dave Neptune

[Bratina]

In a new distributor specified point gap should yield specified dwell, but since the lobes are worn on our old distributors this is no longer the case. Dwell is the important specification, not gap; and you will find that correct dwell will land you at a gap setting well below specification - which is OK.

Now I don't feel so bad that I didn't check the gap today. I'll check dwell and report back.

[Bratina]

Bratina, is there a ceramic piece with wiring mounted to the bracket with the coil? With points you could well still have the original "ballast resistor" still in the loop. Can you shoot and post a pic?

The 10.5~10.9 voltage is fine for the ignition but if it is actually your operating voltage it could be an issue.

Look for the big original equipment resistor or even a small one mounted near the coil. The ignition wire from the keyswitch should hook directly to the positive side of the coil, what you need to see is if that wire (purple I think) hooks to something else first then to the coil. It is very common to lower voltages on point systems to make the points last longer.

Dave Neptune

I'll take a look when I'm at the boat next, I assumed there wasn't one because of the points and OEM-looking coil. There are at least three other wires hanging off the + on the coil. Not sure if that's also a factor.

[hanleyclifford]

I'll take a look when I'm at the boat next, I assumed there wasn't one because of the points and OEM-looking coil. There are at least three other wires hanging off the + on the coil. Not sure if that's also a factor.

I like Dave's idea of having a picture to look at. Those "three other wires" hanging off coil+ could also be having a big impact on voltage if they are driving anything significant such as a fuel pump or blower.

[Administrator]

Typically an alternator will put out around 14 volts of which around 13 volts would be making to coil+ after going thru wires and switches etc. Since that is too much for the coil the practice is to put resistors just ahead of coil+ to bring down to 12 volts or lower.

Hanley, I don't think this is correct.

Bill