1974 50hp Power Pack?

[jsalz]

Hi,
I'm not getting spark on bottom cylinder.
I used a spark tester and absolutely no spark. Both coils were new last year.
I reversed wires to coils in power pack and now the bottom cylinder fires and top doesn't.
So, I've proved that both coils and plug wires are good.
I'm getting no power to cylinder 2 from power pack.
Could something upstream of the pack cause only one cylinder to fire or should I just replace pack?
Compression is 140 on both.
I don't have a dva but do have an ohmmeter.
Thanks for your help.

 

[234rick]

Re: 1974 50hp Power Pack?

It could be a corroded or separated wire inside the rubber coating. Check that coil wire from the power pack. You might be able to gently pull on the wire & if you find a thin spot that is your problem & it can be fixed with a simple solder job. That is if its far enough away from the pack. If its where it enters the pack I think you will have to buy a new one.

 

[jsalz]

Re: 1974 50hp Power Pack?

Thanks,
But I think I've already ruled out the coils and wires.
By swapping the wires under the power pack, the "no spark" did not follow the coil, it followed the terminal on the power pack.
I would like to know if something under the flywheel can cause no spark on one coil?

 

[HighTrim]

Re: 1974 50hp Power Pack?

The situation that you mention is usually caused by a faulty coil or pp.

A weak trigger magnet in the flywheel or timer base COULD cause no spark to 1 cylinder, but are rare I would think.

I would test the pp first, too bad you werent closer to me I have a couple spares laying around that we could use to troubleshoot.

 

[jsalz]

Re: 1974 50hp Power Pack?

I'm actually in Sarnia. Still not close enough. I just don't want to drop 120 bucks and find out its something else. I've done that before

 

[HighTrim]

Re: 1974 50hp Power Pack?

You could ask around to borrow a DVA meter to check the voltage on the orange wire from the pack. Should be 150V or more.

Other options are getting a DVA attachment for your meter from ebay or the like, or you could make your own with a quick run to radio shack. Follow the advice in the following link.

http://forums.iboats.com/showthread.php?p=1712691#post1712691

I also just dug around in the basement looking for a spare pp. Was going to mail it to you to see if it helps, but cant seem to locate it. Will ask my wife what she did with it

 

[jsalz]

Re: 1974 50hp Power Pack?

Well, I think I've narrowed it down to the pp. I read a procedure out of the book on soldering wires to a 1.5v battery. You then remove the sensor wires from the pp and while cranking, you tap the wires onto the terminals. One polarity, one coil will fire, the other polarity, the other coil will fire. In my case, the coil that was not firing before, still would not no matter what polarity and the other one did.
I suppose I still haven't proved out the magnets, but I know I need a new pp either way.
I have a new one on order and will be here tomorrow.

 

[HighTrim]

Re: 1974 50hp Power Pack?

Interesting test, never heard of that. What "book" was that out of?

You could test the diodes in the pp by using your ohmmeter set to high ohms scale. A normal diode will read resistance in one direction and infinite reading in the other.

 

[jsalz]

Re: 1974 50hp Power Pack?

Its from a manual that covers a whole range of Johnsons that I got before I got my oem manual.
I only have 8 terminals.
It did pass these three tests with an ohmmeter though:
Sensor Coil Low Ohm Check
Sensor Coil High Ohm Check
Charge Coil Output Check-with ohmmeter.
I do have a scope meter at work. Could I use that to see actual voltages out of the sensor coils and power pack?

 

[234rick]

Re: 1974 50hp Power Pack?

Sorry wrong thread

 

[jsalz]

Re: 1974 50hp Power Pack?

Sorry, maybe I stated it a little confusing.
The coil that didn't work, worked when I switched them. The coil that worked, didn't work when I switched them. The terminal for cylinder 2 is not working.

 

[234rick]

Re: 1974 50hp Power Pack?

Sorry, maybe I stated it a little confusing.
The coil that didn't work, worked when I switched them. The coil that worked, didn't work when I switched them. The terminal for cylinder 2 is not working.

Ok I think I have it now so it wasn't the clys. that switched firing it was the coils that switched.

 

[jsalz]

Re: 1974 50hp Power Pack?

Just thought I'd give an update. After changing the pp and realizing you need to have the keyswitch to on to use a remote starter, I now have great spark on both plugs. Thanks to everyone who helped out, I'll be fishing tomorrow!

One other thing I found for someone who might have to change the pp. My WOT timing was way out with the new pp installed, so you might want to check it out too.
Thanks again