Johnson 7.5 Kill switch troubleshooting

[76Vector]

Hoping some folks can help me troubleshoot a 1983 Johnson 7.5 which does not kill with the kill switch. Model J8RCTA is the engine in question and I just finished installing a new kill switch in the tiller handle which checks out with a meter. My question is what is the next thing to troubleshoot on the power pack (Part #: 0582452, formerly0582453) since that's where the harness plugs into? I'm not sure if there's a way to measure anything through the power pack black/yellow stripe lead kill wire to ground or another test point? I'm sure folks will say just replace it which I'm anticipating but my old school geeky brain wants to test everything so I know how to troubleshoot this 100% and not just replace parts.

Hoping some folks can share some knowledge. Thanks!

 

[alldodge]

The kill switch connects the Black/Yellow to ground. The switch should be an open connection when running, and make connection to kill motor. The switch grounds the magneto which stops the spark. If the Black/Yellow is connected to the Mag and the Black is a good ground back to the motor, then the motor should die.

If its not dying, then cheack the connections to/from Mag and ground and the contacts on the switch

 

[kbait]

I have seen cd box kill circuit fail, and otherwise work normally. You can turn the idle stop lower, and kill by slowing throttle fully.

 

[76Vector]

Sorry for the delayed response, past couple days have been booked solid. Played around with the engine tonight and confirmed via my meter the switch is functional as installed since I just installed it due to bad switch.

On this engine, the switch wires go to the power pack plug and ground to the lower coil rear bolt, all of which are showing good continuity. Question: If I measure continuity on the power pack black yellow stripe wire and the ground lead from the power pack, I should see a connection, correct? If that should have continuity, then the power pack has an open in the kill circuit as kbait mentions.

alldodge, are you referring to other plug leading to the mag plate from the power pack? If so, which wire out the power pack should have continuity with the kill circuit black/yellow stripe wire? This connector has the following wire colors:

- Brown
- Brown/Yellow stripe
- Black/White stripe
- White/Black stripe

Powerpack part number stamped on it is 582452 for reference. Curious to know what you guys would recommend. Thanks!

 

[alldodge]

If I measure continuity on the power pack black yellow stripe wire and the ground lead from the power pack, I should see a connection, correct?

Should only see continuity if the motor is turned OFF or kill switch is pulled

The power pack is grounded to kill the motor, and open to start it

 

[76Vector]

For the second statement, does this mean I should see continuity from the black/yellow stripe wire to the ground wire with the power pack removed from the engine? All the tests I've done have been with the engine off, not running.

 

[alldodge]

2 stroke
Will run if the black/yellow is NOT grounded
Will not run if black/yellow is grounded

 

[76Vector]

Day off today to tinker and get house stuff done. Engine is running as I type this and I pulled the kill wires out of the boot so I could use a clip lead to short the black/yellow stripe wire to ground and she keeps on purring at idle. Thinking this is the power pack, everything else looks good.

Is there anything that should be inspected under the flywheel? On these I wouldn't think but figured I'd ask. Otherwise thinking it's the power pack.

 

[alldodge]

Have you checked continuity of the Black/yellow all the way to here it goes?

 

[76Vector]

Where am I checking continuity? Black/yellow stripe wire should have continuity to which terminal, ground? That was my thought but that's open, if that's true, then I'm guessing the power pack is toast.

 

[alldodge]

Where am I checking continuity? Black/yellow stripe wire should have continuity to which terminal, ground? That was my thought but that's open, if that's true, then I'm guessing the power pack is toast.

Yes, with key in the OFF position the black/yellow should show zero ohms to ground. If its not then check your key switch

Key should have a black yellow on a terminal and a black on another terminal. When the key is OFF the switch should connect the blk/yel to blk terminals. The blk terminal should go to ground

They are the "M" terminals in the above pic

 

[76Vector]

I think your explaining how to do this with an engine that has a control box and ignition key. The engine I have only has the momentary kill switch on the tiller as part of the grip which I just replaced due to a faulty switch which I confirmed was dead. I confirmed the new switch is functioning as it should and when I took the power pack off I did notice a crack in it on the back where you can see the internals through the epoxy. Not sure if that will make these inoperable but that's what I noticed earlier today when I took it off to clean the terminals for ground.

 

[alldodge]

Sounds like you have tracked the issue as far as it can.
Was hoping with all the folks who has looked at the thread they might offer some insight

I'm unable to find a Johnson diagram for your model but the Merc works the same, may just be different color wires. When the Magneto is grounded, the motor stops