Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak voltage

[mike101650]

I have no spark. I had spark last fall and engine actually started. I started it without any water intending to see if it would start and it did but would not turn off with the key. I ran back to the engine and grounded the kill terminal on the Pack and it only ran about 10 seconds. I don't think that was long enough to hurt anything. Now 5 months later, I am back on the project and no spark using my in line tester. I took advice from someone on Iboats and bought the book. Now the book helps but I don't have the special tools required. I also downloaded the CDI, Inc. trouble shooting guide. This is probably a one time project for me and I don't want to spend a bunch of money to gear up just for these tests. I would rather spend the money on gas when it runs or ammo if it doesn't. I am wondering if a typical in line spark tester will work OK. I have one of those but don't have the thing recommended in the book. Also I don't have a DVA. My meter is a TRUE RMS meter. For a normal sine wave, I would multiply that by 1.41 to convert RMS to Peak. I don't have a DVA and am wondering if anyone has taken both RMS and Peak measurements on the same engine under the same conditions. I know the wave shape determines the multiplier but should be close enough to work. If I knew those readings, I could then convert my RMS to Peak without buying or building a DVA. I am reading 136 volts on my RMS meter across the brown and brown-yellow. Surely that would convert to between 150 - 400 as stated in the voltage measurement chart of the CDI, Inc trouble shooting guide.
Thanks in advance IBOATS.

 

[Bosunsmate]

Re: Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak vol

Hows your cranking speed?
try it with all sparks out and grounded

 

[F_R]

Re: Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak vol

Meaning this in a good-natured friendly way, but as they say you seem to know enough about electricity to be dangerous. My guess is that the brown/brown-yellow voltage you are getting is probably ok. I'll bet you know how to make a DVA adapter from a diode and a capacitor. Then you can test the power pack outputs.

You are sure the black/yellow kill wire isn't the problem, right?

 

[classiccat]

Re: Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak vol

I'm going to go out on a limb (i don't own an o-scope) and say that the trigger traces are a very short duty cycle

 

[classiccat]

Re: Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak vol

this is one of many iboats threads on how to make/use a DVA.

simple-easy-make-dva-adapter-standard-multimeter

 

[mike101650]

Re: Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak vol

Hows your cranking speed?
try it with all sparks out and grounded

Not sure what you are getting at here. Do you want me to hook the spark tester in series with a plug wire to ground with all plugs removed? I have a rev counter. It was reading around 250 so I thought probably marginal and added another battery. Now it is around 285. Shouldn't that be enough to generate a spark?
If I jump with my Pick UP, I can get the cranking rpm up over 300. Still no spark on my in line tester.

I have not heard from anyone if it is ok to use my tester as opposed to the one described in the book.

 

[mike101650]

Re: Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak vol

Meaning this in a good-natured friendly way, but as they say you seem to know enough about electricity to be dangerous. My guess is that the brown/brown-yellow voltage you are getting is probably ok. I'll bet you know how to make a DVA adapter from a diode and a capacitor. Then you can test the power pack outputs.

You are sure the black/yellow kill wire isn't the problem, right?

A few times in my life, I have worked on something until it no longer fixable. I am trying to avoid that on this project.

I tried to get a spark with the kill wire disconnected from the pack just in case it was causing the problem.

 

[F_R]

Re: Electrical tes on a 1977 Evinrude 140. Spark testers and RMS voltage VS Peak vol

Forget all the fancy stuff. You seem to be unsure if you have spark or not. Remove only one spark plug wire and stick a phillips screwdriver in the boot. Hold the shaft of the screwdriver 3/8" from a head bolt. Have somebody crank the motor with the key. Are you getting spark?