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DVA Readings

I found this while surfing aft

I found this while surfing after looking up Carl's link to the DVA adapter.

DVA – Direct Voltage Adapter. Also known as Peak voltage. The term refers to the peak voltage as read by a specialized meter or a multimeter using a adapter to convert the peak voltage in the ignition system to a DC value. Regular meters cannot read the voltages due to the frequency and duration of the pulses in the system.
 
"That post I made about DVA an

"That post I made about DVA and the frequency...
I was gonna read the AC voltage with my meter and look up the math calculation for calculating the peak DC volts from an AC voltage, when I remembered that those math calculations are only good for AC sine waves.
I would bet that this stator does not put out a sine wave AC voltage. I would love to see the output on an oscilloscope.
So, I guess the only way to go is with using the DVA adapter.
By the way, in 35 years experience in the electrical / electronics field as an engineer, I have never heard of "DVA" outside the marine industry. Have I lived a sheltered life?

Hey David, when you get the adapter, would you please measure the center to center distance between those banana plugs that plug into the meter and post it? I would love to know if they will fit my meter. Thanks."
 
"Doug and Michael...i do not o

"Doug and Michael...i do not own a peak reading meter....it would be just another tool that i would use once every 5 years....i ordered one once but cancelled it because i found the problem within an hour after i ordered it..the only motor i maintain is my own....i carry a spare power pack in my boat as a spare...unless you work on outboards for a living i dont see the need for the meter..i may buy the adapter..but if i look at the normal sequence of troubleshooting an ignition problem in an engine before the computer i think we are talking one of three things..the powerpack ,timer base,stator..if the stop circuit is isolated and the powerpack dont fix it then its the stator..time to pull the flywheel...that exactly the sequence of my last 2 bad ignition problems...throw the spare powerpack on the motor...if it fails again then get a stator..a stator will be intermittent but its gonna completely crap out soon if flaky...keep in mind a couple things...you can take resistance readings on the stator....the measurements are published..the 2nd thing is that you can have a stator failure with a problem in the charging side..the charging is completely seperate and you do not need it working to run a evinrude/johnson but a problem in that area can cause current variation in that winding and cause a heat problem in the other winding...so when you lose a stator its a good idea to evaluate the charging side for any problems....make sure the wiring and connections are in good shape ...make sure the battery is good..watch the voltmeter and tac for proper operation..having said all that i prob will order a meter..i a sucker for tools...see ya"
 
"No problem posting the distan

"No problem posting the distance of the plug for the meter. And Yes, I am working on Marine outboards as part of my business.

Listen to the problem I am having with this boat. Center cylinder on a Evin. 70hp is burning up the piston. (looks like a lean condition or poor timing--definetly high heat in combustion) Repair completed, cylinder bored and reassembled--engine ran great for about 1 hr or less and then power problems. Disassembly showed the same problem in the center cylinder only. Rebuilt again--this time we have no spark on the center cylinder. Could we have a trigger that is sparking intermitantly, causing a faulty combustion condition? Power pack is not the cause of no spark--tried a new one--didn't work."
 
"There are a couple of other p

"There are a couple of other possibilities.
-You may have a 'loose' liner in the cylinder and water leak. May happen only when engine gets heated up.
-You may have a 'defective' carb, not giving enough.
- You may have leakage in crank-case (crank-shaft) not giving enough 'vacuum'.
Normally this would (should) have been detected on the spark plugs during testing after assembly.
One thing is clear: You did not find the original cause of break down!"
 
"That is correct--I didn't

"That is correct--I didn't find the original cause. We have looked at temperature, vacuum leaks, fueling, water getting in, reeds, cracked case, etc.. During this assembly, we will move the center carb. to see if the problem travels with the carb.

I am still somewhat confused about why the motor would run on all cylinders (spark) prior to tear down and now the center cylinder has no spark. It's not the coil--problem travels with the primary ignition wire from the power pack. It must be the trigger??"
 
"Michael,

I think that the

"Michael,

I think that the trigger is definitely bad now, but it is possible that the pack caused it to go bad. I always replace the pack when the trigger goes bad just to be safe.

Check the cylinder head for warpage. Tolerance here is 0.002 in.

You can check for spark jump by marking the flywheel at TDC for each cylinder, and using a timing light. It is obvious if the spark is jumping around.

Tony"
 
"Michael:
It is a lot about &

"Michael:
It is a lot about 'reading' the spark plugs. If it runs too hot, it might short out. A shortened plug might cause the Power-Pack to fail. A failed/shortened PP might burn the trigger.......
Burned down pistons are rarely caused by failing ignition, unless You have a power-pack that double-fires. (Ign at 2 or more cyls at the same time). However lean conditions, overheat etc might cause PP or other ignition part of ignition system to fail."
 
"I appreciate all the input.

"I appreciate all the input.
I replaced the power pack--problem still present. Replaced the trigger--problem still present. I am assuming at this point the stator must be the only other possibility (since all wiring integrity is good). I did do a AC signal test coming from the old trigger and I did get signal on all 3 trigger signals into the power pack. I thought for sure the problem would be in the power pack. Wouldn't it make sense that if you are getting signal from the trigger to the power pack, but no fire on #2 coil--it would be the power pack? I moved the primary wires into the coils and the #2 coil fired with the wires moved. Coil is good!"
 
i think i would back off a bit

i think i would back off a bit and do three basic checks...compression just to make sure..no other logical reason..just would do it...timing on the 2 working plugs to make sure no double fire..then i would hook up a sparktester and see just how much fire you got on the 2 working pistons..just because you see the plugs firing dont mean you have good fire..remove all the plugs and check for a 7/16 inch fire..if you dont have that then back off and see just how much you do have...once i had that i would start the swap business all over again in case i got my hands crossed and/or lost logic in the swap process..keep in mind that swapping can be misleading with a weak signal..you prob have a bad stator but i would redo as i suggested because of the cost..
 
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