1977 Johnson v-4 115. bad power pak again. Why?

[mudweiser]

Bought a Ranger with a 1977 Johnson v-4 115. Cleaned the carbs, replaced with carb kit. Ran ok. First trip out, it dropped a cylinder. Replaced the coil, still no spark in cyl #3. Replaced the power pak and it ran good on the hose. Took it out to the lake and it ran strong for about 10 minutes. Then it would drop a cylinder out of the hole, some times it would fire, sometimes it would not. I noticed the Tach was not working so i replaced the rectifier. Now thinking it was a timer base or stator, i replaced those also. Still has no spark in cyl #3. Switch the coils, and cyl #3 still has no spark and the problem does not follow the coil. I suppose i have another bad power pak. The powerpak was a new Sierra PowerPak and it only worked for about 10minutes. What would cause these to fail? I can't keep replacing them, pretty spendy. But i have to get it runing good. Any idea what keeps knocking them out?

 

[Joe Reeves]

Re: 1977 Johnson v-4 115. bad power pak again. Why?

(MCD Powerpack Failures - 1973 +)
(Magneto Capacitance Discharge Systems)
(J. Reeves)

The usual cause of having those type powerpacks fail repeatedly is having a very small of voltage applied to the Black/Yellow wire at the pack. Test as follows.

Disconnect the Black/Yellow wire at the powerpack.

Insert either a ampere meter or a volt meter set to its lowest DC voltage reading between that Black Yellow wire and ground.

With the ignition key in the OFF position, observe the meter reading. Now turn the ignition key to the ON position and again observe the meter reading.

Any reading, movement of the meter needle, would indicate that battery voltage is being applied to that Black/Yellow wire. If a reading is present, remove the other end of that Black/Yellow from the raised terminal of the ignition switch.

If the reading ceases to exist when the Black/Yellow wire is removed from the ignition switch, replace the switch. If the reading continues to exist, there would be a short of some kind in either the engine or instrument wiring harness.... to determine which, simply unplug the large RED electrical plug at the engine which would eliminate the instrument cable.

 

[mudweiser]

Re: 1977 Johnson v-4 115. bad power pak again. Why?

Turned out the power pak was fine. Had another bad coil. Ignition system is now working properly and is timed and synced properly. Starts right up now at the bump of the key. On to the carbs now. Rebuilt them both last season, but it's still running rich on the top end. Needles are leaking i think.

 

[Joe Reeves]

Re: 1977 Johnson v-4 115. bad power pak again. Why?

"Needles are leaking i think"???

There are no adjustable needle valves on the 1977 115hp model. If you're speaking of the "Float Needle Valves", remove the carburetor face plate, then pump the fuel primer bulb up hard. If the floats are set wrong or have faulty float needle valves, that would be obvious as fuel would flow out of the carburetor(s). However, if this was the case, the engine would run lousy at any rpm.