1974 Johnson 40hp will not kill

[boydog]

you guys helped me out on this couple of months ago and i found the problem and fixed it! but now its doing the exact same thing, wont kill with the key switch. new switch ohms out ok, blue and blu white ohm out ok up to master plug, after master plug they ohm to all zeros when the key is on, weird. i traced both wires to the flywheel and all look ok but still all zeros on the meter.
what could make it do this?
thanks

 

[F_R]

Not sure what you are telling us, but the key switch connects the blue and blue/white together when turned "Off". There is no connection when turned "On".

Connecting those wires together shorts out the ignition and the motor quits.

 

[boydog]

With key on or in off position the blue and blue white wires read all zero after the master plug. before the plug the wires read as they are supposed to. guessing maybe corrosion in the master plug, ill check it tonight and advise.
something making it not read correctly

 

[Crosbyman]

disconnect the kill wires from the flywheel ...........start the engine….

short the wires at the plug (motor side !) ……………………..does it kill the engine yes/no ???


if NO…. problem in the fw side of the wiring … pull FW inspect for broken wire or connection .. bad crimp ??

if YES reconnect the wires (plug) … & go back to the switch



disconnect the wires on the switch start the engine

short the wires

...........................................does it kill the engine yes/no ???

yes….then switch is bad (does not short the wires in the OFF position

no...then the wires from the switch to the engine are bad (one is likely broken in a bend somewhere )
test individually by testing ohms between the ends of the individual wires (all the way between the switch end and the motor plug (switch side !) .

could also be a bad plug connection causing loss of continuity.. inspect for corrosion.. if plug contacts are bad

get new connectors or spilce the wires together


to test for broken wire while the engine is running try turning the steering to the right side while the key is OFF ...if engine does die find the broken wire in the cabling harness ​

 

[boydog]

Will do! Thanks ill do it this afternoon when i get home, thanks

 

[boydog]

from key switch to master plug, key on reads 1., key off to master plug 0.00. which is correct.
from other side of master plug (male side) to flywheel 0.00 key on or off. i cannot find a break anywhere.
with wires disconnected at the plugs, would not start, plugged back in, cranked, while running i unplugged 1 wire and it started missing, unplugged other and motor quit. removed both plugs wired direct now, no change.
with master plug unplugged, male side still reads 0.00 all the way to flywheel key on or off.
im at a total loss now

 

[F_R]

???If the engine runs, everything is ok at least as far as the blue and blue/white wires at their connections to the external coils. So why do we have the flywheel off?

The motor is killed by connecting those two (Blu & Blu/W) external coil wires together, via the harness and key switch.

 

[boydog]

FR correct, but when i turn the key off motor keeps running.../ pulled flywheel looking for pinched bl/bl wh wire none found

 

[Crosbyman]

OK lets start again…I am getting disoriented with some of the terminology :doh:



step#1.... USE 200 ohm range on the meter you are looking for continuity or no continuity in two short pieces of wire going to the switch via the harness

20k ohms it is like using a telescope to read a book . All you need is a magnifying glass to look close up front ! we are dealing with and looking for a ohm value between 0-2 ohms

step#2 with the meter probes on the two blue wires going under the FW and switch OFF measure the resistance and report back

to kill the motor you must read 0 ohms or almost 0 ohms (full conductivity) while the switch is OFF so no need to start the motor for this test. we know the motor works :joyous: just measure and report back

with the switch in OFF & If you measure .. infinity ... open " no conductivity" … that is the highest resistance then the internal short inside the switch is not reaching the destination….mainly you probes and the meter (ultimately the points which need that short circuit inside the switch …... to kill the ignition.

that said if you do not see a short on the blue wires going under the flywheel…...via the harness plug…... then all the way up front to the switch :facepalm: then one or two wires are broken or the switch is bad.


we are down to basic wire testing.... you will need to hunt down the open condition and you have few options

1- broken wires..flywheel to harness ( unlikely but possible since the mag plate moves them a lot )
2- bad connections crimps somewhere
3- bad harness internal joint (corrosion)
4- bad key switch (not shorting the 2 kill terminals in OFF mode ) M I believe they are marked FR can confirm

 

[F_R]

I say again, the motor runs, so there is no wire problem between where they leave below the flywheel to the external coils. From there, the blue wire is extended all the way to the ignition switch, via the harness (and plugs). Ditto for the blue/white wire, except it also passes by the center terminal of the vacuum cut-out switch. Do you have two blue/white wires connected to the cut-out switch (one coming from the #2 coil and one going onward to the big plug)?

 

[boydog]

yes both wires connected to cut out

 

[Crosbyman]

Not sure what you are telling us, but the key switch connects the blue and blue/white together when turned "Off". There is no connection when turned "On".

Connecting those wires together shorts out the ignition and the motor quits.

boydog…. as per FR comment do you have readings (ohms) on the blue & blue-white with switch ON and OFF ???

 

[boydog]

[No message]

 

[Grub54891]

It may not matter, but it looks like somebody poked the blue wires with a test probe. I personally hate that. It allows corrosion/moisture to enter and compromise the wire internally. If there are other wires around the motor like that, it could be where the problem lies.

 

[boydog]

you are correcdt, thats why i ordered a new harness, wires are very soft in spots, corroded in others....

 

[Grub54891]

you are correcdt, thats why i ordered a new harness, wires are very soft in spots, corroded in others....

Good let us know if the new harness cures it. When you get it running, take the old harness and pull each wire like a rubber band. You just may find a stretchy spot in the wire.

 

[Crosbyman]

you are still using 20K range…. you should use 200 ohms

in any event based on pics you are showing dead short 0.00 ohms with the key off which is good
but a pure 0.00 ohms on a 20k ohm range may not be a pure 0.00

my only suggestion is to disconnect the blues tape them up and tuck so them under the flywheel so

they won't rub​

wire up 2 new small l gauge wires to the points where the blues were connected bring them out under the flywheel
via an openning

start the engine…. and short the 2 wires to simulate a KEY OFF condition the engine should die

I hope it does ! if it does not something is screwy with the points because they should mutually ground themselves when the kill wires are linked (shorted)

 

[boydog]

ill try that before the new harness gets here and advise, thanks

 

[Crosbyman]

and…….

 

[boydog]

sorry, new wiring harness installed, have not had a chance to crank it yet. maybe sunday! i will keep you guys informed