Electrical problem on a 4W Freedom 160

[shotgunsmitty]

I have an issue with an electrical problem that I hope one of you can help me with. Sorry to drop in on a first time post like this, but after lurking for a while, I think you guys might be able to do me some good:

My spark is grounding out. It's not the coil. It's not the alternator/generator. It's not in the wiring harness around the motor, it's up from that. I can disconnect the wiring harness and get no continuity between ground and primary coil wire, but plug it back in and it grounds out.

Any idea where to start looking? Why would the spark go back up front? Maybe in the throttle as a safety feature? I'd like to know what would cause total disruption like this. Any ideas? I'll be happy to do a "live" troubleshooting with anyone along the way and report answers to your questions as we go along.

[gonzo]

Either the kill switch is faulty or the ignition switch. The ignition switch grounds the inginition to stop the motor.

[shotgunsmitty]

Doesn't seem to be a kill switch (bail cord, right?).

Ignition is definitely a possiblity, what about the tach? If the tach was grounding out, would that cause it, too?

[gonzo]

Yes, that's a possiblility. You can troubleshoot the problem by disconnecting one thing at a time.

[shotgunsmitty]

Gonzo, thanks for your replies. Question, though, doesn't the ignition switch open the circuit, therefore interrupting the spark, in order to kill the engine? Wouldn't terminal B open to I on the ignition switch when the key was inserted and turned one notch?

The reason I ask is because I've removed the key switch, I have three terminals, B (Black/Ground, maybe?), I (ignition, I assume), and S (start, perhaps?). It checks good. No continuity between anything when the key is out. When the key is inserted and turned one click, continuity exists between B and I.
When the key is turned to "start", then continuity exists between B and I, B and S, and I and S.
So, I'm pretty sure that the key switch is okay.

Back on the motor, when I plug the foreward wiring harness into the aft wiring harness, then the signal (positive) side of the coil shorts to ground. When I unplug it, it goes away.

Where's the kill switch typically located?

[gonzo]

I just realized I thought you were talking about an outboard. What model engine do you have?

[shotgunsmitty]

Aah, okay.

It's the 3.0 Liter 4 cyl, 130 or 140.

Well, I'm changing my story! Sorry to do this, but after redoing the troubleshooting, I found an error in my part (and a big one at that). It seems that it IS around the engine, and it's NOT forward of the harness, it's AFT of it.

Sorry to change my story, but here's what I've got: Same problem as before, the negative side of the coil is shorting to ground. That's the signal wire that comes from the distributor to the coil that tells the coil to fire and dump the high voltage to the spark plugs. I get continuity between this wire and engine/system ground. After segregating the wire, I've found that I only get continuity when the resistor wire to the choke heater is connected. When disconnected, no continuity. The resistor wire shows .055 ohms when on the lowest (200) setting. This is about 1/20th of an ohm, and the manual says that it should be showing 1.8 to 2.0 ohms.

Looks to me like this resistor wire could be bad...but why would they send the secondary signal to the choke heater on a carburated motor? Even if it is via a resisted wire? This is definitely where it's grounding out, this much I feel I've confirmed. What else can I check?

[gonzo]

The choke gets powered through the puple wire, the same that sends power to the ignition. Is your engine a Volvo or a Mercruiser?

[shotgunsmitty]

Oh, sorry, I never specified...it's the Merc.

I never checked to see how much resistance is going through the choke to ground...but I'm sure since it shorts the purple wire to ground that it would have to be inf continuity.

I picked up some ballast resistors from the Blank Stare Store. I'm making a resistance pack of 1.5 ohms and plan on wiring this into the purple wire, possibly replacing the entire wire, I read of someone doing this and it working out well. Your thoughts on this?

[gonzo]

Mercruisers have an ignition interrupt switch to help shifting. It temporarily cuts the ignition. If it is out of adjustment, the switch is stuck or the intermediate shift cable is sticking it will cut the ignition and short it. It grounds the black or blue wire from the distributor.

[shotgunsmitty]

Yup, checked that one, it checked out good. I found the one you're talking about, even removed the switch and checked it off the motor and it's fine.
I did find a problem with the starter and it looks like it's going to need replaced. In the mean time, what's next?

[gonzo]

The kill switch is typically in the dash or the control box(throttle and shift). It is inline on the purple wire. However, it shouldn't ground the ignition, only interrrupt the power. Disconnect the positive on the battery, hook up the harness and test the purple wire is grounded. Then disconnect the purple wire from the switch and test if it is grounded. If it is on both, there is a short somewhere.

[shotgunsmitty]

Okay, did that and it checked fine. I'm fairly certain that the ground is aft of the harness, somewhere around the motor. I have disconnected the harness and the coil is shorted to ground, so at this point it's segregated from the throttle.

[gonzo]

Is this a points and condenser or electronic ignition?

[shotgunsmitty]

Points and condenser. Already checked them, though, Found a set of new points and a new condenser in the boat when I bought it...but to be honest, I think that when the new starter gets here I'll put a new set of points and a new condenser in, anyway.