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71 Johnson 125 starting issue

C

Contusioncharger

Member
Hi, I have a 71 Johnson 125 I just rebuilt. I first tested it to see see if I had spark while just crank, and I did not. After troubleshooting I found that the pulse pack was bad. I got a new pulse pack from cdi, I removed the clipper circuit and I now have spark.

So so I decide to try starting it with muffs just to be sure it will start when I get the boat in the water. The Engine would not fire until I released the starter switch, it would just fire once. It also would fire once when I turned the off. I can actually hear the spark every time I turn the key off.

I found a post post here where it says to put a diode from the starter side of the relay to the pulse pack wire on the terminal strip. I did that, and it will only fire with the starter going, it kicks of the flywheel once it starts. When I let go of the key it dies. I put a jumper wire from the red wire to purple on the terminal strip and it fires right up and idles good, just need to disconnect the battery to shut it off.


I have a new battery. With the key on I have 12.5v at the red wire and 11.5 at the pulse pack. Any one have any ideas. Thanks.
 
Below is the answer to that problem, taken from me database.............

********************
(Voltage Drop To Battery Capacitance Discharge)
( Pulsepack When Electric Starter Is Engaged)
(J. Reeves)

On the older Battery Capacitance Discharge ignition systems (1968-1972), the electric starter reaches a point, even with a top notch battery, whereas the starter will draw excess voltage/current/whatever which results in a voltage drop to the pulsepack. The cure is to purchase a diode which is capable of handling 12 volts and installing it between the starter terminal of the starter solenoid (NOT the battery cable terminal) and the wiring terminal that supplies voltage to the pulsepack.

The diode must be installed so that the current flows from the starter terminal of the solenoid to the pulsepack... NOT vice versa. When that diode is installed in this manner, when the key is turned to the start position, the voltage that is applied to the starter is also applied directly to the pulsepack via the diode effectively eliminating the voltage drop and energizing the pulsepack with the required voltage needed for its proper operation.

********************
 
joereeves said:
Below is the answer to that problem, taken from me database.............

********************
(Voltage Drop To Battery Capacitance Discharge)
( Pulsepack When Electric Starter Is Engaged)
(J. Reeves)

On the older Battery Capacitance Discharge ignition systems (1968-1972), the electric starter reaches a point, even with a top notch battery, whereas the starter will draw excess voltage/current/whatever which results in a voltage drop to the pulsepack. The cure is to purchase a diode which is capable of handling 12 volts and installing it between the starter terminal of the starter solenoid (NOT the battery cable terminal) and the wiring terminal that supplies voltage to the pulsepack.

The diode must be installed so that the current flows from the starter terminal of the solenoid to the pulsepack... NOT vice versa. When that diode is installed in this manner, when the key is turned to the start position, the voltage that is applied to the starter is also applied directly to the pulsepack via the diode effectively eliminating the voltage drop and energizing the pulsepack with the required voltage needed for its proper operation.

********************
Click to expand...


i have done this, as I said. The diode is the reason why it only runs with the key in start. When I release the switch it dies, but I have power at the pulse pack, so it should stay running. If I remove the diode it only fires when I release the start switch and if there is still enough compression left it will fire once when I turn the key off.
 
I am think about installing a relay. Connecting the red wire and the pulse pack to the relay contacts. And using the purple wire from the start switch to energize the relay.
 
Don't go off tinkering with the engine, dreaming up additional electronic setups.

It sounds like you have the voltage wire (purple) attached to the "S" terminal of the ignition switch whereas it should be attached to the "A" terminal... or the terminal "Ign" depending on what switch you're using. And if so, the only time you would have 12v going to the pulsepack would be when the key is in the START position.

What are the terminals marked on that ignition switch?
**********************
EDIT: Having second thoughts....

1 - Are you saying that the engine is actually running while the electric starter is cranking the engine.... OR....
2 - Are you saying that the engine is simply trying to fire to start, as in a spark plug firing now and then.... but is not actually running.

If #1, My reply above about the ignition switch holds true.
 
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joereeves said:
Don't go off tinkering with the engine, dreaming up additional electronic setups.

It sounds like you have the voltage wire (purple) attached to the "S" terminal of the ignition switch whereas it should be attached to the "A" terminal... or the terminal "Ign" depending on what switch you're using. And if so, the only time you would have 12v going to the pulsepack would be when the key is in the START position.

What are the terminals marked on that ignition switch?
**********************
EDIT: Having second thoughts....

1 - Are you saying that the engine is actually running while the electric starter is cranking the engine.... OR....
2 - Are you saying that the engine is simply trying to fire to start, as in a spark plug firing now and then.... but is not actually running.

If #1, My reply above about the ignition switch holds true.
Click to expand...

Yes to #1. But when it starts the starter drops down and it run on its own, not with the starter. Release the switch to ign it dies.

I just checked the switch. Purple is on ign, white on start, red on battery. I ohm’d the switch. I have open in off, Continuity in ign in on. And in start on ign and start. I don’t think the relay is a bad idea. It would Eliminate the need for the diode, by supplying power to the pulse pack right from the battery and using the the purple wire from the ignition switch to energize it. But Im just a aircraft avionics engineer dreaming. But I rather have thing working the way it should before I would try that. Just seems strange.
 
Okay then, you have the old original type ignition switch... three (3) terminal.

If you have a full 12v supplied to that "ign" terminal (purple wire) in both the START and RUN position... and that same 12v is present at the purple wire terminal leading to the pulsepack..... there is no reason for that engine to stop running due to a lack of voltage to the pulsepack.

If the "Clipper Circuit" is still installed on that engine, get rid of it. OMC came out with a bulletin that it caused more problems than it cured. If still installed, it's possible this problem is one of them. Its original purpose was to eliminate possible voltage surges to the charging system.

That type ignition (Battery Capacitance Discharge) does demand a top rated battery in very good condition, with a rating of at least 75 ampere hours, otherwise damage to the pulsepack will occur.
 
joereeves said:
Okay then, you have the old original type ignition switch... three (3) terminal.

If you have a full 12v supplied to that "ign" terminal (purple wire) in both the START and RUN position... and that same 12v is present at the purple wire terminal leading to the pulsepack..... there is no reason for that engine to stop running due to a lack of voltage to the pulsepack.

If the "Clipper Circuit" is still installed on that engine, get rid of it. OMC came out with a bulletin that it caused more problems than it cured. If still installed, it's possible this problem is one of them. Its original purpose was to eliminate possible voltage surges to the charging system.

That type ignition (Battery Capacitance Discharge) does demand a top rated battery in very good condition, with a rating of at least 75 ampere hours, otherwise damage to the pulsepack will occur.
Click to expand...


I did remove the clipper circuit. Yea it doesn’t make sense.
 
I rebuilt the engine, #1 piston had broken rings. So I had everything apart to clean and paint. While I had the machine shop bore the cylinders. I did say I rebuilt it. The whole throttle/advance arm is new to me. Not like a car. I am still learning. I have the repair manual, read through it a few times. I seen your post on setting timing at full throttle while cranking, I set that. And thought the rest would fall in place. It was about 4 degree before TDC. I set it to 5 advance, like the manual said. And readjust full speed advance as your post described. And it fired right up and stayed running.
 
I just got the boat in the water. I am still having this issue. I believe everything is set right. If I jumper the red to purple at the engine it starts and runs good. If I remove the jumper it shuts off. I have power at the purple wire in on and start. Thinking it was the ignition switch I put in a push button switch for the starter but it didn’t help. It runs and goes good. But after 20 min of running I pull the jumper and it stays running and will start without the jumper. The next I need to use the jumper to start. It also seems at that time the engine begin to bog. I give it gas and it wants to stall. If I can get it past the bog and on plane. It will only go to 2500 rpm. When before it would easily get to 5000. Not sure if it’s heat related. Temp is at 120. Just can figure out why it won’t start with out the jumper if I have power there.
 
At the ignition switch, the 12v voltage "Purple" wire should be hot only when the key is in the ON or START mode. At the engine that same 12v "Purple" wire should be connected to the pulsepack "Purple" wire terminal. Check it.
 
It is. But I think I figured it out. Not sure if it will fix the starting problem. But the battery isn’t charging. Checked the rectifier and it bad. The shift diode is bad also. I have those on order. The engine will run good with a full charge battery then slowly start to Stutter
 
Keep in mind that the ignition system on that engine demands a top notch battery, fully charged, with a rating of at leasst 75 amp hrs. Anything less will, in a short time, result in damaging the pulsepack.
 
Got the new rectifier, battery charges good now. Still the same with starting i have all the right voltages it will only run with the key in start, the starter kicks down but spins. Still if i put a jumper between the red and purple it starts and runs fine. U have tried 3 ignition switches, and also ohm'd checked them. They check good. The weird thing is after going for a ride around. i pull the jumper and it stays run, and will start normal.
 
Contusioncharger said:
I did and I said I do. Seems like after the engine ran awhile everything works like it should. When it cold it doesn’t.
Click to expand...

I don't think you're paying attention or you're having trouble understanding what I'm trying to get across to you.

When I say:......
At the ignition switch, the 12v voltage "Purple" wire should be hot only when the key is in the ON or START mode. At the engine that same 12v "Purple" wire should be connected to the pulsepack "Purple" wire terminal. Check it.
I am telling you:......

You must have 12v constant at the battery wire connection (A terminal usually marker "BAT" or just plain "B".

In the ON or START position, you must have 12v at the "Purple" wire that leads to the pulse pack. If you do, the engine must run!

What is the terminal marked that the purple wire is on?...............Better yet....What are the terminals marked on the back of that ignition switch and what color wires are attached to them?
 
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I have been. Ive re-wired jets for 25 years. I know what I’m doing. Re-read my post 8. At the terminal post match the wire diagram. At the red wire I have 12v all the time. Key off no power at purple. Key on 12 volts at purple. It will only run with the key in start. Like I said I ohm’d out the switch. It’s good. If I put a jumpeter at the engine between purple and red, it runs. I remove the jumper it dies. But I have power at the purple wire with the key in run and start by its self.

If I drive it for while with the jumper in. It will stay running. When it would before. And it will start fine with out that jumper. After it’s been running awhile. Battery volts is at 13 when running. I also have tried the diode thing made no difference.
 
Reading this long story makes my head hurt. The symptoms scream out IGNITION SWITCH. But you said you have tried three switches. OK, so I'm going to go out on a limb and make a guess. Guess: Are you using the correct three-terminal switch? I'm thinking the continuity is being broken as you move between "ON" and "START" and back to "ON". During that brief interval the pulse pack loses it's 12V input and spark quits and engine stalls. The jumper wire is eliminating that brief loss of power to the pulse pack.

BTW, if I am not mistaken, the pulse pack does not put out a spark instantly when you feed power to it. There is a slight delay to prevent the engine from running backwards. Plenty of delay for it to stall during that bief loss of input from the key switch.

If this is a good guess, no award necessary. Sorry, not intersted in a job working on jets either.
 
It making my head hurt to. I have ohm’d the switches have they are good. No drop in continuity between start and ign. I just tried same thing. But after it running few minutes I removed the jumper and it was working fine. You say delay. Should I be leave the key in there ing for a bit before starting to build on power.
 
Just tried again without the jumper. I left it in fast idle and it started. Left there for two minutes brought idle down run good for a little the Spudering. Just touched the jumper it and it smoothed out. Left it one for awhile and it was fine.
 
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