Burning points??

Bassman/NZ

Bassman/NZ

Well-known member
My crab dissy was built by Bubbas and has done about 1,500 miles. Because it suddenly refused to start, I took it off the engine and found the right-hand pair (as viewed from the front of the car)of points were burnt and badly pitted. Now I know that Jim uses quality points, so I'm suspecting something has caused this.
12v, neg earth system, running to a ceramic ballast resistor, running to neg side of a 12v Bosch coil, pos side of coil to condenser. Do I have the coil the right way round? Should the ballast resistor perhaps be after the coil? What should the optimum voltage to the condenser be?
Help!!!
 
Well, the coil is wired backwards for starters. What is the resistance of the coil and what is the resistance of the ballast resistor?
 
Are both sides of the point burnt equally or have metal moved and buillt up on one side ?
If metal has moved to one side of the point the balance of the circuit is wrong (coil/capacitor value).
If both sides are equally burnt in a short time to high load is probably the cause.
 
The condenser may just be the bad item. If you have a 1.5 Ohm primary side type coil resistance and a 1.4 to 1.5 Ohm ballast, they should be good to go. Polarity mis-match usually just causes a weaker spark but who knows with the parts available now days. I'd check the components out and see what they add up to just to be safe and definitely replace the points & condenser.
 
JSeery said:
Well, the coil is wired backwards for starters. What is the resistance of the coil and what is the resistance of the ballast resistor?
Click to expand...
The coil has 3.0 ohms across the terminals, and the ballast resistor shows 1.7 ohms.
 
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flatheadmurre said:
Are both sides of the point burnt equally or have metal moved and buillt up on one side ?
If metal has moved to one side of the point the balance of the circuit is wrong (coil/capacitor value).
If both sides are equally burnt in a short time to high load is probably the cause.
Click to expand...
One side has a peak, the other, a corresponding valley.
 
So far, it looks like my coil is wired back to front, and the ballast is sort of ok, but the coil is showing too high of a resistance? Or is this OK for a 12v system with a 12v coil?
 
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14v / 4.7 ohms = 3 amps, so that shouldn't be an issue. Do you have a starter bypass wired in? Is it wired correctly?
 
You have metal migration on the points so capacitor value is not as it should be.
The coil resistance is on the lower end so that shouldn´t be an issue.
The balance of the points is set by coil/cap combination if cap value is low metal goes to one side if value is high the other side.
Try a new cap and points.
 
flatheadmurre said:
You have metal migration on the points so capacitor value is not as it should be.
The coil resistance is on the lower end so that shouldn´t be an issue.
The balance of the points is set by coil/cap combination if cap value is low metal goes to one side if value is high the other side.
Try a new cap and points.
Click to expand...
Thanks. I'll try a Bosch GH208-C condenser, that seems to work well for others. Also new points, and reverse the terminals on the coil.
 
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