76 Johnson 70 HP - Lost all spark

[eavega]

Hello Folks
My 70EL76D motor has developed a new problem. I have completely lost spark on all three cylinders. I was out fishing yesterday and actually impressed at how well the motor was performing (seems to like to run in colder water). We hit three fishing holes, plus having to do a couple of quick starts when the trolling motor got fouled up with some fishing line and the wind was pushing us into some rocks. We had just gotten done with a 3-mile WOT run back to the ramp. I dropped my buddy off so he could get the trailer in the water. As I was idling near the ramp, the motor just up and quit. It actually seemed to speed up for a moment (still at idle) and then quit. Couldn't get it to start again. Trolling motor got the boat back to the ramp and we got the boat home.
At home I ran through the basics. Pulled the plugs. Compression is still 110 110 105 as it has been for the last year. Spark test, nothing. The plugs and they had a nice brown color to them, so they were not fouled.
With no spark on any of the three cylinders, I am pretty sure its not a bad coil. I did check the overboard switch to eliminate that from the equation, but just came across the test of disconnecting the red plug and going straight from the starter solenoid to the battery and checking for spark to eliminate the ignition switch and neutral safety switch. I'll be doing that when I get home.
Now, given the loss of spark on all three cylinders, if I can eliminate the non-motor stuff (ignition switch, overboard switch, neutral safety), does the fact that the tach is still working tell me anything about the ignition components? I know the tach is still working because when I crank the engine, the tach needle goes to an appropriate "somewhere under 500 RPM" level, and stays there until I stop cranking. That would tell me the ignition system is creating some kind of power, and the rectifier is still working (I've read that the first indication of a blown rectifier is that the tach stops working).
A visual inspection did not show an anomaly with the stator (I have read that when they fail, its usually accompanied by dripping green goo. All the green goo seems to be in place). The tach doing its thing would lead me to believe the rectifier is still working, so that leaves the powerpack.
I know the PROPER way to verify what is wrong is to use a DVA Meter and follow the CDI troubleshooting instructions. Unfortunately I don't have access to a DVA-capable multimeter, and I am trying to avoid having to spend $80 for a tool that I am going to use once, and is going to tell me that I need to get a $120 part. Along the same lines, I would rather not have to purchase a $120 powerpack if I can do some other basic troubleshooting that can help narrow down what is causing the failure of the ignition system.
Any comments or suggestions would be greatly appreciated.

Rgds

 

[Will Bark]

Re: 76 Johnson 70 HP - Lost all spark

Other than than the testing, check the ground wire of the power pack to make sure its not corroded and is making good contact.

 

[boobie]

Re: 76 Johnson 70 HP - Lost all spark

Without the proper test equipment and a manual all you can do is replace parts until you find the bad one.

 

[eavega]

Re: 76 Johnson 70 HP - Lost all spark

The manual I have. Unfortunately the manual calls for specialized "Johnson test tools" which I am sure can be substituted for more common tools.

I did read in the manual about testing resistance on the sensor coil and charge coil. I can do that with my multimeter. I did also dig through enough threads to find an old thread that had a link to a company that sells a DVA adaper for $25. I'll pay that for some peace of mind.

So in the end, I guess I'll do it right and avoid throwing parts at it.

Rgds

 

[boobie]

Re: 76 Johnson 70 HP - Lost all spark

Good idea.

 

[eavega]

Re: 76 Johnson 70 HP - Lost all spark

Okay, so while I am waiting for the arrival of the DVA adapter, I did go ahead and perform the resitance tests on the various circuits. I have some odd results that I wanted to run by someone who knows better than I, and ask a question as to testing using the DVA.
1. On the various references I have, one of the tests is to test the timer base coils (trigger coils?) resistance. According to the guides I have (CDI and Manual) the acceptable values are OPEN, and 0, which would indicate either a good coil or a failed coil respectively. on the 2K Ohm setting on my multimeter, I got a reading of 1350, which is neither open or short circuit. I got this consistently on all three leads. Do I have a bad timer base here, or did that test tell me anything other than I definitely don't have a short circuit?
2. Again, testing resistance from the Timer base coils to the common lead, I was supposed to get a reading in the vicinity of 10-20 Ohms. The manual actually calls for 7.5 - 9.5 +-1, but they specify a temperature of 70 degrees so I am assuming some variance there and will follow the CDI expected readings. Besides, CDI guide says 10-20 Ohms, and I hit that range. I had erratic readings that jumped around from 100 to 10, back and forth, and a bunch of places in between. I had about the same range for all three leads, and all three seemed to settle down the longer I left it connected, but the reading kept moving lower and lower. again, same behavior on all three leads. Should I re-do this test and wait until I get a steady value? Is my multimeter suspect? (I have a cheep one from Harbor Freight, so I don't know if I need to upgrade my testing gear. It serves for reading voltages and short circuits...)
3. Although my readings were out of spec for the timer base, they were consistent across all three leads on both tests. When a timer base fails, does it usually do so consistently, or does it fail one coil at a time? (remember, I have lost spark on all cylinders, which is why I suspect the power pack). I priced a new timer base assembly, and if I thought the cost of the power pack was high, this is three times as much!
4. Dumb question, but I have to ask; you do the DVA test with the engine cranking, right? You need those coils spinning to generate voltage, I would assume.
5. When you are using the multimeter with DVA adapter to measure DVA, do you use the appropriate DC settings? there are two different ranges we are looking for; 0.6V for the trigger to the trigger common, 150V-400V for the trigger to ground, and the across the stator leads. Nothing specifies if that should be VDC or VAC.
6. Are there any precautions you need to take for cranking the engine with the various leads disconnected? I don't want to damage or render inoperable any other part of the ignition system because something was not properly grounded, or some stray voltage leaked somewhere and blew out another componen...

Thanks so much in advance for any help you all can provide.

Rgds

 

[eavega]

Re: 76 Johnson 70 HP - Lost all spark

Okay, I seem to be the only one answering my questions, so I'll use the thread to track my progress.

I resolved the erratic readings from the multimeter. Turns out the connectors for the test leads had corroded some, so my readings (especially for resistance) were off. Lesson learned. You get what you pay for. Borrowed a buddy of mine's recently calibrated multimemter, and readings were spot on for trigger resistance (9.5 Ohms) and for Stator resistance (685 Ohms). Also had valid tests for short circuits on both. That only leaves the DVA measurements to verify that my stator and timer base are still good.

On further reading and searching of threads, I did have a couple more questions, if anyone is reading this:
1. One thing I did test is whether there was any stray voltage on the kill wire. With the key off I get nothing, but with the key switched on, I get .002 V. Now, CDI troubleshooting guide says to be concerned if you get a voltage reading above 2 V, Joe Reeves says be concerned if you get ANY voltage on the kill wire, as this will damage the powerpack. Is the .002 V sufficient to start tracing where I may have some stray voltage?

2. Since it seems that the likely culprit of my no-spark is the power pack, can anyone suggest what can kill a powerpack, and what dies in the powerpack that would prevent it from allowing spark on all cylinders? The powerpack looks like nothing more than a series of pulse-activated switches which allow the proper voltage to pass from the charging coils to the ignition coils to be properly stepped up. I can understand how the powerpack could fail and prevent spark on ONE cylinder, but what has to die to prevent spark to all three?

Inquiring minds want to know.

Rgds

 

[idonthaveaname]

Re: 76 Johnson 70 HP - Lost all spark

My 70 Johnson did the exact same and I went through all of the decisions you have. In the end, rather than trying to figure out the problem (time), I found a good mechanic. He discovered the timing base was dead. I wasn't disappointed in that getting to it you have to pop the flywheel which was impossible to remove for me. Anyhow there are about 4 or 5 parts that can cause the problem and I knew that much. FWIW

 

[eavega]

Re: 76 Johnson 70 HP - Lost all spark

In the end, it was a bad powerpack. the DVI tests showed that the stator and trigger were putting out the correct voltage as long as they weren't connected to the powerpack. Replaced the pack, spark is back.

Rgds