how to test powerpack 77' 115

[mudweiser]

I thought i had a fuel problem due to the rich smell and the engine running better once it open up but i now found it's spark related. It's a 1977 Johnson 115. it would run ok at low RPM, then when you slammed it it would bog then take off. This slowly got worse. Today i brought a timing light with and put it on each cylinder's coil wire. Cylinders #2 and #4 were firing fine even when it was stuttering. Cylinders #1 and #3 were cutting out. When the engine bogged, either #1 or #3 cylinder had no spark. Swicthed the coils from bank to bank and the problem did not follow. Guessing i have another bad powerpack. How can i test the power pack with a ohm meter? i found a dis-connected coil ground wire a while back on cylinder #3, could this have knocked out my power pack, it was a new power pack last season.

 

[HighTrim]

Re: how to test powerpack 77' 115

A rough running engine may be due to interaction of the Power Packs because of faulty isolation diode in Power Packs. The diode may be checked by using ohmmeter set to high ohms scale. Check it as follows:

1. Disconnect leads from power pack terminals 6 and 11

2. Connect ohmmeter leads between the 6 and 11 power pack terminals. Note the reading.

3. Reverse the ohmmeter leads and note reading. Infinite or very high reading in both directions indicates diode open. A low ohms reading in both directions (approx 100) indicates a shorted diode. A normal diode will read resistance in one direction and infinite reading in the other.

4. If the diode is defective you willl need to replace the power pack.

Joe Reeves is the master and can explain why the pack fails best.

(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 an 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.

 

[HighTrim]

Re: how to test powerpack 77' 115

More troubleshooting, taken from the CDI Troubleshooting Guide.

NO SPARK OR INTERMITTENT ON ONE BANK:

1. Check the timer base?s resistance from the #1 to the #3 sensor wire, and from the #2 to the #4 sensor wire. Reading should be 10-20 ohms on each set (or 30-40 ohms for CDI Electronics Blue Timer Bases).
2. Check the DVA output from the timer base. A reading of at least 0.5V or more from the #1 to the #3 sensor wire, and from the #2 to the #4 sensor wire (while connected to the pack) is needed to have spark. If the output is low, you may try to reset the air gap between the timer base sensor and the triggering magnet using a sensor gap gauge or use the procedure outlined in the previous page.
3. Check the DVA output on the orange wires from the power pack while connected to the ignition coils. You should have a reading of at least 150V or more. If the reading is low on one cylinder, disconnect the orange wire from the ignition coil for that cylinder and connect a load resistor to that terminal. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading indicates a bad power pack.

 

[iwombat]

Re: how to test powerpack 77' 115

I went through something like this last week. Try switching the sensor leads going into the power pack from the timer base and checking spark again - you can't actually run the motor like that. If the problem shows up in a different place, you have a timer base problem.

See: http://forums.iboats.com/showthread.php?t=256231

 

[mudweiser]

Re: how to test powerpack 77' 115

Here's my findings wityh a Craftsman auto range digital meter. Wires disconnected testing the powerpak on 6 and 11 meter was 6.2 and climbing reverse leads and it was 25.0 and climbing.

Timer base wires disconnected #1 and 3 8.0 #2 and 4 8.2.

Tested on the box with wires disconnected terminals 11/12 23.15 9/10 21.20 4/5 17.30 2/3 18.10

Black/yellow w/key off dropped to negative digits in voltage. Key on was also negative voltage.

When the powrpak was installed terminals 7/8 were swicthed around. Could this have blown it? Also the #3 coil ground was not hooked up, could this have done it? I hate to drop $100 in a new pak and wreck it again.