Burned points

[boozer1966]

1984 mercruiser 140 alpha mr. Why did my points burn up. Less than a year old. Very little use. Set gap, dwell and timing within spec when installed. Now have occasional rough running and points are almost completely gone. Any thoughts?

 

[Don S]

Re: Burned points

Some probably replaced a burned up resistor wire with regular wire.

View attachment 140 Wiring.pdf

 

[stonyloam]

Re: Burned points

Could be the capacitor is shot. The capacitor acts as a buffer (to absorb the voltage spike) to reduce arcing of the points when the points open. If it is not functioning the arcing will burn up the points.

 

[gm280]

Re: Burned points

Could be the capacitor is shot. The capacitor acts as a buffer (to absorb the voltage spike) to reduce arcing of the points when the points open. If it is not functioning the arcing will burn up the points.

I have to answer YES to that question. The capacitor (condenser) could be open and not doing anything. It would cause the points to burn easily. Some Mulitmeters have a capacitor scale on them and you could check to see if the capacitor is good or not very easily. A shorted capacitor would have been most obvious by now because you would not get any spark at all from the point/capacitor setup. But being opened is a little different to detect without a meter...

 

[thumpar]

Re: Burned points

Measure voltage at the coil with the ignition on. It should be 7-9 volts and not 12. If it is 12 Don S is right.

 

[boozer1966]

Re: Burned points

Many thanks to all.