no spark , hot wired

[ricsorbi]

I have a 5.0 OMC, age unknown. I get no spark off the coil wire. I disconnected all wires from the coil positive side and ran a jumper to the battery. No spark. Tried another coil, same set up same, same no spark. Am I right thinking I have to get into the distributer and find out why there is ground/no ground? New points and condensor by the way. Am I going the right way and what am I looking for? Appreciate any help. Thanks.

 

[ricsorbi]

Re: no spark , hot wired

Am I right in thinking that if I measure voltage at the positive post of the coil I should get about battery voltage as long as the points are closed and then turning the motor by hand, lose voltage when the points open? Again, thanks for the help.

 

[daveswaves]

Re: no spark , hot wired

Hey Polar guy, close but no cigar, your problem is in the dist end of the system, not the battery end. You will have around 8 to 10 volts at the plus term of the coil as the unit is cranking. Try to think of the points as a switch that is normally closed, or on. When the bump on the dist cam hits the points, they open and allow the current that was flowing through the coil to stop, very quickly. When the current stops the collapsing magnetic field induces a high voltage into the secondary windings of the coil and that voltage makes the spark. If you put new points in make sure that they did not slip and that they are indeed opening and closing when the dist turns. Check for wiring on the points or dist shorting to ground.

 

[ricsorbi]

Re: no spark , hot wired

daveswaves, thanks. So ohming throught the wire from the distributor (disconnected from the coil) I should only get continuity to ground when the points are closed. If there's a ground/continuity when the points are open, the points are shorted to ground and not letting a spark build.

 

[daveswaves]

Re: no spark , hot wired

Exactly right Polar Guy, sounds like you are close to getting it sorted out.

 

[ricsorbi]

Re: no spark , hot wired

Daveswaves, everything ohms out okay, still no spark. Could it be that both of these coils are bad, sure. Bought an $11 generic GM at the auto store to try and there you go. I'll bet the marine coil isn't $11. Thanks for letting me know I wasn't barking up the wrong tree.

 

[daveswaves]

Re: no spark , hot wired

Glad you got it fixed, very unusual for both coils to be bad unless they have overheated. Make sure the coil you put on has an internal balast resistor (should be marked as such on the coil) or if not use an external balast resistor or resistor wire. Your local marine supplier will be able to help you with this.