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Johnson 90 hp J90TLCOS spark problems

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fernandos

New member
hi, guys bought this engine very cheap with no remote control.
was told ran great when was on the boat.
anyway, this is my first time playing around with a motor with no controls.
my first thing was checking the compression on all cylinders and I got between 90 to 95 psi.
it sounds low but is an old motor.
next checked spark and only have spark on 3 cylinders .at first I thought maybe a bad coil.
the no spark is the top left-hand side I'm not sure if its called cylinder 1.
so I disconnected the coil with no spark and connected the coil from the lower left and still no spark.
so that means the problem is coming from somewhere.
followed the wire from coil took me to a box I believe is called Power Pack Assembly.
is there a way to test if this is the problem?
 
your description of trouble shooting loses me somewhere.

I assume what you have done in your coil test is...... you switched the wire from the powerpack that leads to a firing coil to the non firing coil, and the non firing coil still didn't fire. That indicates a bad coil. If your test was anything different, humor me... do this test as it keeps things simple.

On the other hand, with the above test... if the non firing coil fires, switch those wires back to where they were so that the non firing coil once again does not fire, then... test the timer base assembly by switching the wires between the powerpack and the timer base. Now, if the non firing coil now fires, that indicates a faulty timer-base assembly. But if nothing differs with the timer-base wires switched and the non firing coil still doesn't fire... then usually it's a powerpack failure.

Hopefully I haven't confused you... it sounds drug out but it's really a simple test.
 
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hi joe thanks for the help.
maybe I can explain better.
the coil that is not sparking i replaced with the one that works, and still no spark.
them i replaced the coil that didn't spark to the connector of the coil that was sparking and it sparked.
so my diagnosis is coil is in good working order.
hope this makes sense I'm sorry this is the best I can do.
I'm, not a mechanic, I'm sure you have guessed it.
I'm trying to fix this as my old 70hp Johnson has seized.
i can't afford to get it fixed so i been lucky to find this engine.
i also enjoy working and diagnosing, fixing stuff etc
i have no idea what timer-base assembly is but i will find out.
here pick of power pack
 IMG_20181013_174645.jpg
 
The pictured object is the powerpack... don't attempt to open it.

Yes I understand your test procedure of the coil. And the fact that that you can get it to fire proves the coil to be okay.

The timer base is the component under the flywheel that moves as the throttle cable and the attached linkages move. As it moves, the spark is either advanced or retarded depending on the direction of movement.

As it stands, your problem is either a failed powerpack or one of the timing sensors in the timer base. The sensors are not replaceable.

To tell which is at fault... (your engine has dual powerpacks)... switch the powerpacks. Now, with the packs switched, if the problem followed the pack to the opposite bank of cylinders, the pack is faulty. If the spark problem remained the same, the timer base is at fault.

Note: The exception would be, if the spark remained the same... that a connection within one of the rubber connection plugs was flawed... such as a pin/socket pushed back out of place slightly, OR a wire broken off from the pin or socket and held in place by pure friction of the rubber plug... check all connections.

Let us know what you find.
 
ok update the power pack big plug is damaged.
i went around cleaning all the pins of all the plugs and the big female side of one of the pins (blue wire) was damaged
the female pin was squashed the male pin would not attach.
so i have found and fixed the problem.
thanks joe you have saved me from buying stuff i don't need like new power pack etc.
thank you
im goint to try and start it put video of her running
 

hey mate, I see you live in Florida hope you're not affected too much by the hurricane.
all the best stay safe
 
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fernandos said:
hey mate, I see you live in Florida hope you're not affected too much by the hurricane.
all the best stay safe
Click to expand...

Glad to hear you found the problem and have your engine running well.

I live in an unincorporated area named Valrico which is growing rapidly... about 20/25 miles east of Tampa, quite away from the actual shoreline (Gulf Coast). All we got of that hurricane here was some welcome shade (cloud cover), a welcome drop in temperature, and a gentle breeze... but I do appreciate your concern. Happy boating. (Joe)

Oh, you can always find me on eBay also... Seller = Joe_OMC32
 
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