1985 70hp Johnson Ignition Issue

[carpedium]

First, hello everyone - I have lurked around and tried to figure my issue out based on existing posts, but nothing quite like this that I can find on a similar engine.

Problem:

Motor intermittently does not start when cold and there is no spark. When it is running its completely fine.

Info:

There is not voltage on the black/yellow wire at the power pack

All connections are completely 100% good

Right now the motor is running both jumped from the solenoid with the red connector disconnected and also with it connected and controlled by the control box.
I am using a standard interstate deep cycle battery
There is resistance between the black/yellow wire and ground


Suspected issues:

Maybe its an intermittent problem with my ignition switch? I will have to wait for it to happen again to see if I can start the motor with the red connector off, correct?

Can this be a problem with the power pack? Stator? any other compnent? Has anyone heard of this happening to one of these other electronic components and having them come back from the dead?

At one point my depth finder said that my battery voltage was up to like 16.8
I use the motor primarily for trolling, so it runs at a slow speed for hours.

Anyone have any ideas?

Can a high battery voltage cause the thing not to start (no spark) but not stall? Would this voltage normally just blow the power pack?

Thanks in advance.

Thanks,

Matt

 

[Daviet]

Re: 1985 70hp Johnson Ignition Issue

I am guessing that the engine will turn over properly, but you have no spark. Disconnect the black/yellow wire at the power pack and see if you get spark, if so you have a problem with the kill circut. Check for spark with a tester and do not try and start the engine, if it would start with the black/yellow wire disconected, the only way to shut it down is by choking it down.

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Per my original post I currently have spark and everything is running perfectly. I previously shut it down by pulling the spark plug boots.

Have you heard of an intermittant issue with the kill circuit? Is there supposed to be a resistance from ground to the black/yellow wire with the red connector disconnected?

 

[Daviet]

Re: 1985 70hp Johnson Ignition Issue

If you disconnect the large red cannon plug you have eliminated all the electrical system, you need to have the cannon plug plugged in to test the system. If the only way it will run is to have the cannon plug disconnected, plug it back in and disconnect the black/yellow at the power pack, and see it you have spark.

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Right now the motor is running both jumped from the solenoid with the red connector disconnected and also with it connected and controlled by the control box.

It will run both ways right now.

With all due respect, are you reading my questions? I only ask because I know of other forums that have some kind of bots that can be malicious.

 

[Daviet]

Re: 1985 70hp Johnson Ignition Issue

I guess I misunderstood your post, You are going to have to troubleshoot the engine when it woun't start. If it starts you can't troublesoot the system. I am sure someone with more experience will come along and ansewer your questions.

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

I guess I misunderstood your post, You are going to have to troubleshoot the engine when it woun't start. If it starts you can't troublesoot the system. I am sure someone with more experience will come along and ansewer your questions.

I apologize. Again, I did not mean any disrespect at all. Thank you for your help.

Does anyone think such High battery voltage could cause this problem? Its almost like it will start after it cranks enough to get it down to 13 volts. Would this make sense?

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Bump

 

[eavega]

Re: 1985 70hp Johnson Ignition Issue

Isn't that high voltage your charging voltage i.e. when the motor is running? My 70 hp Johnson has an unregulated charging circuit, and voltage can get up to 18v at WOT. Once the motor is off and no longer charging the battery, it stabilizes at 12.5v.

Rgds

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Isn't that high voltage your charging voltage i.e. when the motor is running? My 70 hp Johnson has an unregulated charging circuit, and voltage can get up to 18v at WOT. Once the motor is off and no longer charging the battery, it stabilizes at 12.5v.

Rgds

I didn't know if that voltage affected my battery at all. Thats good to know though, I thought the rectifier would keep the voltage down to 14 or so. I also though high voltages like that could blow my power pack.

What year is your 70? Mine has a metal round thing below the power pack, so I thought that was the rectifier or voltage regulator.

Anyone know what this intermittent issue could be then?

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Thanks for you help so far!

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

:facepalm:

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

I just went out, and it still is firing up fine now. Any suggestions on how to try to force the problem in order to trouble shoot it further?

I'd just hate to be using it and have it give out on me and create a safety issue. The OB repair guy nearby said he is booked for the summer.

 

[Daviet]

Re: 1985 70hp Johnson Ignition Issue

Since the problem occours when cold, you are just going to have to keep trying it. Easier to force a hot starting issue than a cold one.

 

[James R]

Re: 1985 70hp Johnson Ignition Issue

Most often this is an issue with the motor kill circuit. Try disconnecting the black yellow at the switch box and using a multimeter, preferably an analogue unit with a pointer, on 1K setting, measure the resistance between the black/yellow and the motor case. That is with the red plug connected of course. With the ignition switch off you should get a dead short Zero ohms. With the ignition switch on there should be an open circuit, no continuity. As switches do become defective, try switching the switch on and off a few times and see if there are any changes. Not necessary to turn the motor over in fact it would be advisable to disconnect the battery for this test.

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Most often this is an issue with the motor kill circuit. Try disconnecting the black yellow at the switch box and using a multimeter, preferably an analogue unit with a pointer, on 1K setting, measure the resistance between the black/yellow and the motor case. That is with the red plug connected of course. With the ignition switch off you should get a dead short Zero ohms. With the ignition switch on there should be an open circuit, no continuity. As switches do become defective, try switching the switch on and off a few times and see if there are any changes. Not necessary to turn the motor over in fact it would be advisable to disconnect the battery for this test.

I tested with my fluke 87 on data logging mode and was not able to replicate a short between ground and the black/yellow wire at the control box. I tried this in the start and run positions.

Hmmm..

 

[eavega]

Re: 1985 70hp Johnson Ignition Issue

I didn't know if that voltage affected my battery at all. Thats good to know though, I thought the rectifier would keep the voltage down to 14 or so. I also though high voltages like that could blow my power pack.

What year is your 70? Mine has a metal round thing below the power pack, so I thought that was the rectifier or voltage regulator.

Anyone know what this intermittent issue could be then?

Mine is a '76. That round thing three wires coming off of it (two yellow, one red) is the rectifier.

-Rgds

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Has anyone heard of any particular issues with the green stator under flywheel? Any significance that it is green in color?

 

[carpedium]

Re: 1985 70hp Johnson Ignition Issue

Someone had mentioned that these items can fail intermittently, thats why i ask

 

[James R]

Re: 1985 70hp Johnson Ignition Issue

If you cannot get a dead short to ground on the black/green in any switch position either your test is wrong, you have a bad switch. bad connection at the red plug, or a wiring problem. I don't trust digital meters for these tests because the are self ranging and don't provide what the analogue meter provides.