New owner: 1988 Sunbird OMC Cobra 3.0 ignition issue

[Wellarmedlamb]

Hello, new member here and first time boat owner. Bought a 1988 Sunbird w/ OMC Cobra 3.0(paid less than the trailer alone was worth).

Preface: I'm pretty mechanically inclined having spent many years working on cars.

The boat was sold on the premise that the owner thought it had a cracked block but couldn't really tell me why, just "wann't runnin right". So i get the boat home and start opening it up and see that he removed the head, starter, coil, and so on. I was to simply reassemble it and try and figure out what is actually wrong with it.

I installed the starter and coil and the engine cranks nice and smooth(head not installed).

So I move on to checking the ignition system. Spark plug sitting on the block: no spark. Screw driver in the coil wire and near the block: no spark.
Checked the (+) on the coil with my DVOM: 0v with key-off, 12v with key-on(which either stays 12v or quickly drops to either 9v or 6v. It seems to be different each time the key is turned on), 9v with key-start.

Also noticed that the starter terminal which goes to the coil reads 4v with the key-off. Is this normal?

Here's what I think I know, correct me if I'm wrong: There should be 0v with key-off. There should be 9v with key-on/run. There should be 12v with key-start.
External resistor reduces to 9v with key on/run to preserve the points. Secondary post on the starter becomes energized while cranking and supplies full battery voltage only during cranking.

Last thing I noted is that while there is no spark while cranking, there is one spark when the key is returned to on/run.


Could this have something to do with the ESA and related switches? (I have no real knowledge of this part of the system. As I understand it the ESA reduces ignition power to stumble the engine for gear change?)

Thanks in advance.
Jesse

 

[bruceb58]

It seems to be different each time the key is turned on), 9v with key-start.

The voltage you measure at the positive side of the coil with the key on will depend if the points are closed or not.

First thing I would do is to install a new set of points and condensor before you did anything else. To get the ESA out of the equation, just unplug it until you get the engine running.

 

[Wellarmedlamb]

I found the sticky about troubleshooting the ignition system and saw that anything from 4v - 9v is correct with the key on/run so I guess I dont have a problem there but I'm still thinking that there should be full battery voltage at the (+) terminal on the coil when cranking.

Disconnecting the gray wires from the (-) terminal on the coil does not change anything. Does this fact rule out the ESA system?

Need new points and condenser perhaps?

 

[Wellarmedlamb]

thanks bruceb58

 

[Wellarmedlamb]

New points(gapped to 0.019) and condenser, coil and rotor button. Perfect. Thanks