Jeffafa
Cadet
- Joined
- Jul 10, 2021
- Messages
- 12
Hi guys, trying to figure out why my 85 Mercedes has no/ very weak spark. Good 12v to coil + and - when points are open. With points closed (after ensuring they are clean and adjusted), coil positive drops to around 4.5v and negative shows around 1v.
I have bypassed the coil negative by removing the grey wire and the wire to the points, attached a jumper wire to negative and removed positive wires and attached a lead straight to the battery. When grounding the coil negative and watching spark from the tower it is very weak and hard to even see,, when everything is connected, spark will not deliver to the plugs. Next I disconnected all coil wires and tested primary and secondary resistance. Primary: 2.4 ohms, secondary: 11.8k ohms, after doing research these readings look to be in range. Is it possible the secondary windings are good enough for an ohm meter but not healthy enough to deliver high voltage?? In my experience with cars when ohming a coil and it's in spec, it's usually a good part. But seeing that I've bypassed the points and the power supply I don't know what else it could be other than a bad coil.
Also what are the odds someone can attach a wiring schematic as I am having trouble locating one!
Thanks in advance and happy boating!!
I have bypassed the coil negative by removing the grey wire and the wire to the points, attached a jumper wire to negative and removed positive wires and attached a lead straight to the battery. When grounding the coil negative and watching spark from the tower it is very weak and hard to even see,, when everything is connected, spark will not deliver to the plugs. Next I disconnected all coil wires and tested primary and secondary resistance. Primary: 2.4 ohms, secondary: 11.8k ohms, after doing research these readings look to be in range. Is it possible the secondary windings are good enough for an ohm meter but not healthy enough to deliver high voltage?? In my experience with cars when ohming a coil and it's in spec, it's usually a good part. But seeing that I've bypassed the points and the power supply I don't know what else it could be other than a bad coil.
Also what are the odds someone can attach a wiring schematic as I am having trouble locating one!
Thanks in advance and happy boating!!