Boat electrical issue

[bsch]

I'm can not get a spark out of the coil. Here's the rundown:


The battery is fully charged.

The ignitions fuse is good.

The wiring harness fuses are good.

The distributor cap, rotor, condenser, wires, and plugs are new.

The coil is new.

The solenoid is new.

When the ignitions switch is off, there is no 12 vdc going to the positive terminal of the coil.

When the ignition switch is off, there is a continuity connection of the negative terminal on the coil to the motor (chassis) ground.

When the ignition key is activated we measure 12 vdc on the positive terminal of the coil, when tested only to chassis ground.

However, we do not get continuity from the negative terminal to chassis ground, when the key is on.

We do not get 12vdc between the negative & positive terminals of the coil when the ignition key is turned on.

The ignition key does switch properly between the hot wire to the starter solenoid and ignition wire when keyed on.

When I attach a wire directly to the negative (ground) side of the coil from the chassis ground (while the key is turned on), and have 12 vdc going into the coil between the positive and negative terminals, there is still no spark to the plug through the ignition wiring.

Even after changing coils, we get no spark regardless of what we try,

Even though the condenser is relatively new, could it be bad?

Why would I lose continuity on the ground side only when the key is turned? Is there something that makes/breaks the ground side as well?

Any comments/suggestions?

Thanks,
Brad

 

[MikeHalloran]

The breaker points break the ground side. If they are disconnected or open, grounding the minus side of the coil stores magnetic energy in the coil. Removing that wire should produce a spark.



Mike Halloran
Pembroke Pines, FL, USA

 

[TheBlacksmith]

Need more info - engine make, year, electronic or breaker point ignition, etc. Ground with key off, no ground with key on, could be a faulty Prestolite or other elctronic module. Try disconnecting ground wire on coil and use a jumper to ground the coil, then remove, there should be a spark as Mike says.

 

[Comcokid]

On Boats-
1) Check that the ground on the block is not painted over. A common problem is that the block ground point(s) that they are painted when the engine is made, and later the wiring harness ground lug is bolted to the painted surface (a big problem on I/O engines). You may measure 12 volts at the coil because of sneak-paths through sensors to ground, but the moment you turn the key the voltage will drop to zip. This may occur not only on the 16 gauge ground wires for modules, coil (brackets), and sensors, but also on the battery ground.

2) Check the ground wire at the connectors in the boat harness. Boats frequently use AMP (Tyco) Universal-mate-N-lock connectors. If the pins are not inserted completely until they snap into the nylon housing the terminal will push out slightly when the connectors are mated. Unmate the connector(s) and wiggle the individual wires. Unlike a car with a metal chassis, grounds have to be continuous throughout the whole boat.

3) Sometimes a molded vinyl connector is used at the engine. Make sure vinyl flashing is not covering the ground in this connector.

4) I have seen engine wire harnesses where there was a wire splice in the middle of a wire within the taped-harness. The wire is pulled from a big reel, and splices may occur every few thousand feet. When they produce the harness, such splices are not cut out, and I have seen defective splices within a harness.