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1987 Johnson 70, no spark

C

christianfreiss

Member
Hey guys,

I’ve got no spark until I disconnect a wire from the warning horn. After that it runs beautifully. Does this indicate failed horn or is this a symptom of another issue. My horn is wired in the remote control wiring harness. It has a purple (hot), tan (neutral?), and black (ground) wire attached. Voltage is being induced into the tan wire which seems to be killing spark. I did try disconnecting the tan wire on the VRO, temp switch, and I don’t have a separate oil tank. I also disconnected the kill wire (black with yellow stripe) on the key switch. Nothing helps. I couldn’t find a good wiring diagram for it either. Maxrules only extends to 84 for a wiring diagram.

Thanks in advance,
Christian
 
christianfreiss said:
The motor is new to me. It didn’t come with a tank so I ordered one. Until it comes in.. I did try disconnecting the VRO plug. No help
Click to expand...
If you hook a tank back up to it there is a certain procedure for testing the VRO pump. I would keep it as a pre mix motor for now. The wiring diagram for an 84 70 hp should be pretty close to yours.
 
Ok. I will looking into testing the VRO when the tank arrives. Premix is a great idea.

I looked at the wiring diagram and I just can’t see where the tan wire and kill wire (black with yellow stripe) interconnect. Somehow power is leeching to the kill wire, which is killing spark. I may need to pull the harness apart to get my answer. The wiring diagram indicates that it is isolated. I suppose it is possible the insulation is cracked in the bundle somewhere and making contact
 
Like I said, the motor is new to me, so I haven’t really been running it. More so, I ran it the other day for the first time on mixed gas. I only meant until I’m certain the VRO is mixing correctly (50:1), I’ll run mixed

I can’t see how it could leak through the ignition switch mainly because I disconnected the kill wire there and still no spark, but also because the tan wire doesn’t connect to the switch.

I’ll pull the wire bundle apart later on tonight and trace the wires. If I understand how OMC intended the warning horn, it’s an isolated system. It charges as soon as key goes on, and sounds if it finds a ground. That’s it. Somehow voltage is bleeding from tan wire to black yellow and then ground.
 
You cannot allow power to enter the black/yellow.....it will destroy the power pack. Spark is
defeated when black/ yellow is GROUNDED.
 
Gentlemen, just wanted to share a photo. I’ll post again when it’s running as it should the full finding. Near the red plug where the wire passes through the cowling, I found this under some electrical tape and hose shown in the photo
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I found the damaged wires by ohm(ing) between the tan wire and kill wire while flexing along the wires length. When I found a place that shifted the resistance I opened up the area. It looks like maybe it chafed then burned the insulation off of 4 of the wires. After cutting out the damaged portion of wires, soldering and heat shrinking the wires back together, I recovered the affected area with the chunk of hose material. After that I checked for voltage at the kill wire near the power pack. I measured approximately 0.2 volts. I checked for spark and it looked good. Run check was good. Maybe this will help someone some day.
 
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