1984 70 HP Johnson with no spark on bottom cylinder

[LOWfishin]

Hi all, I'm new to this forum so please bear with me. I'm trying to diagnose a problem with my '84 Johnson 70 hp 3 cyl. It has no spark on the bottom cylinder. I have of course tried a new plug and have replaced the coil and sparkplug wire for that cylinder, as well as checked all wires and connections between the pickup coil on the flywheel and the CD box and any other wires that are part of the ignition system. Still no spark. The motor starts and runs on the other two cylinders. Anyone have any ideas? Could the CD box still be bad? thanks for any ideas or help!

 

[durban]

Re: 1984 70 HP Johnson with no spark on bottom cylinder

could be the stator or power pack . i would suspect the power pack first .

 

[durban]

Re: 1984 70 HP Johnson with no spark on bottom cylinder

could be the stator or power pack . i would suspect the power pack first .

what i do to check a power pack on the Earlie models like in your case is swop the wires around that come from your timer base going into the power pack around . your model has plugs on you can do it but you have to cut the plugs off . doing it my way will tell you straight away where the problem is if it sparks then you know its the senor if it doesnt spark then you know its the power pack take all the plugs out when you do it this way & don't forget to put the wires back to original

 

[LOWfishin]

Re: 1984 70 HP Johnson with no spark on bottom cylinder

Ok i need a bit of clarification. When you say timer base, are you referring to the pickup under the stator? And by powerpack i assume you are referring to the CD box. I am not very familiar with this type of ignition system, so please bear with me. The pick up has 4 wires 2 brown, 2 yellow. The 2 brown wires go to the CD box, but have a connector about midway between the pick up and the CD box. The 2 yellow wires go to a junction block on the side of the engine case that has multiple wires connected to it. Some of these wires tie into a small metallic "coil" looking part mounted below the CD box, and the rest go into the wiring harness. So are you saying i should switch the two brown wires that go to the CD box around to do your test??

 

[durban]

Re: 1984 70 HP Johnson with no spark on bottom cylinder

i will try and explain my way , with the 1970 ties motors its easy , because you can see the wires in the timer base , they got smart & sealed it all up in the newer motors , but they still work on the same principal . inside they have 3 HALL SENSORS one for each spark plug . there are 4 wires coming from the timer base , white , purple , green & light blue now 1 of these wires is the what i call the common wire it feeds all 3 sensors power in other words it goes into 1 sensor then no 2 & 3 that comes from the stator .the other 3 wires are connected individually to each sensor , find the common wire first . once you have it , then the other 3 wires are your plug wires , those 3 you can swop around , but not the common wire , that one stays with its m8t .

the 4 wires coming from the stator 2 yellow & 2 brown leave them where they are , if you have swopped any 2 wires around from the 3 & that plug then fires then you know your sensor for that plug is at fault .once you have fond the fault make sure you connect the wires like you found them originaly other wise your fireing order wil be mixed up , if you get stuck , all you have to do is make sure the common wire is connected with its m8t , then connect 1 wire at a time leaving 2 out to find your spark at no 1 plug once u have it then connect 1 more wire to find your spark at no 2 plug & so on

i do it this way it saves money on the 1970 ties motors i do not go & buy a new timer base , i just buy a HALL SENSOR 5 or 10 dlrs & off i go fishing

get a 1970 ties timer & base strip it then you will know what iam on about , if you find that its your timer base , just fit a 1970 ties one cut the plug off on your power pack end or fit 1 to the 1970ties one the black & white wire on the 1970ties timer base is the common wire make sure you connect it with the common wire on the power pack end , it will work . i knowooo

 

[durban]

Re: 1984 70 HP Johnson with no spark on bottom cylinder

i will try and explain my way , with the 1970 ties motors its easy , because you can see the wires in the timer base , they got smart & sealed it all up in the newer motors , but they still work on the same principal . inside they have 3 HALL SENSORS one for each spark plug . there are 4 wires coming from the timer base , white , purple , green & light blue now 1 of these wires is the what i call the common wire it feeds all 3 sensors power in other words it goes into 1 sensor then no 2 & 3 that comes from the stator .the other 3 wires are connected individually to each sensor , find the common wire first . once you have it , then the other 3 wires are your plug wires , those 3 you can swop around , but not the common wire , that one stays with its m8t .

the 4 wires coming from the stator 2 yellow & 2 brown leave them where they are , if you have swopped any 2 wires around from the 3 & that plug then fires then you know your sensor for that plug is at fault .once you have fond the fault make sure you connect the wires like you found them originaly other wise your fireing order wil be mixed up , if you get stuck , all you have to do is make sure the common wire is connected with its m8t , then connect 1 wire at a time leaving 2 out to find your spark at no 1 plug once u have it then connect 1 more wire to find your spark at no 2 plug & so on

i do it this way it saves money on the 1970 ties motors i do not go & buy a new timer base , i just buy a HALL SENSOR 5 or 10 dlrs & off i go fishing

get a 1970 ties timer & base strip it then you will know what iam on about , if you find that its your timer base , just fit a 1970 ties one cut the plug off on your power pack end or fit 1 to the 1970ties one the black & white wire on the 1970ties timer base is the common wire make sure you connect it with the common wire on the power pack end , it will work . i knowooo

in other words to make it all really simple , like you can swop coils around to check , so can you with sensors , providing the common stays with its m8t