CDI ignition call for help/understanding

[Rick.]

I recently had issues with my motor not getting spark. I ended up taking it to a shop for diagnoses and they told me the power pack had failed. I've ordered a new one. In the beginning I did try to do my own trouble shooting on this problem but it seemed the more I read and checked things the less confident I became. My coil ohm'ed out way out of spec. but the boat mechanic said they often do even as temperature goes up and down. In the end he said the coil was fine. On my own I would have ordered a new coil due to the reading I got and the CDI spec's. I'm wondering if there is a tried and true troubleshooting procedure that any of our forum members are confident in. The mechanic I went to told me he only uses the ohm measure to prove the diagnostics he has done reading the volt measures with his DVA. We have meters at work that are high end Fluke and say they read peak volts yet CDI's site says no digital multi meters are capable of reading peak voltage without a DVA adapter which again ruined my confidence. I could not find anywhere to probe for volts when I was trying to test so opted to go with ohm checks due to the easy of getting to connectors. After talking to the mechanic regarding the ohm checks I felt that was an inconclusive way to check things and potentially very expense as well. The mechanic said he uses "back probes" to test voltage. I have no idea what they are. I've searched around and can't find back probes anywhere on the web. It would perhaps help if I new what I was looking for.

Sorry for the long post but I would love to see a Top Secret File thread on this CDI stuff and in the mean time would welcome any help or advice you all can offer. I did not give the model of my motor as I really want to know how to troubleshoot the CDI components, not a specific engines CDI. Hope this makes sense and doesn't have everyone running for cover. I do realize it's all complicated. Thanks to all. Rick.

 

[jjhjrcmh]

Re: CDI ignition call for help/understanding

Re: Testing a stator? Need to build a DVA...help
http://forums.iboats.com/showthread.php?t=371144 Read this.

Also if you think its the coil replace with one you know is good and check. Do you have a timing light? This is a very helpful tool. I found one of my coils would work until it got warm then would stop. Replaced and all is well.

 

[AlTn]

Re: CDI ignition call for help/understanding

Rick...will share this with you..I'm dumber than <insert comparative here> when it comes to electrical stuff...the moneky see monkey do I can sorta handle...manual for 1978 9.9 had diagnostic drawings and values...came to understand that a DVA would replace a couple of the test instruments...I ordered a jumper wire set from CDI..<this includes one wire with a spliced female end onto a male end that allows you to insert a probe point to get a voltage reading w/o piercing the insulation of the wire being tested> I also got a dva adapter from them. You can isolate and test any circuit with and w/o the powerpack connected using these jumpers. Soooo...you can read trigger voltages, charge coil voltages into the pack and voltages to the coils using these. I managed to condemn the powerpack and one coil using these,( course it only had 1 pack and 2 coils to begin with ). I used a little rubbing alcohol and a small headed nail to push the pins out of the plugs and needle nosed pliers to push them back in.
What little I know about powerpacks I learned on the forums from F_R, Daselbee, Ezeke, and many others. I feel confident that you can diagnose electrical problems with the proper equipment, OMC factory manuals, the writings of the above mentioned and the understanding that electrical gremlins can and will try the patience of a saint and the pocketbook of a patron.

 

[daselbee]

Re: CDI ignition call for help/understanding

A back probe is any type of tool that you can use to push into the back side of the connector and get contact with the metal terminal inside there to measure the electrical parameter you are trying to measure without disconnecting the connector.

I also use an OMC breakout box heavily to get my measurements. Google it for a picture...I think Stevens still makes them.

I think your peak reading Flukes will do perfectly well in taking the measurements you need. If the specs say 200 DVA volts at the coil primaries, and your Fluke consistently reads 450...well then it is not going to work. If it is very close, then you are good to go.

I rarely use the ohms testing of electrical parts as it is not helpful to me at all. For example, the battery charging coils of the stator ( yellow pair) have such a low resistance that it is hard to tell if I am seeing zero or .25 ohms. Am I reading the resistance of the meter leads? I always have those type of questions. It is very unlikely that any of the modern digital meters will read properly on the timer base leads. Timer bases have diodes and SCRs inside them, and depend on many electrical factors to read properly using an ohmmeter.
I don't even bother to ohm out a timer base.

As a rule of thumb, the first test I do is a spark gap test using any kind of the popular testers that allow you to set for a 7/16" gap.
If I find a dead cyl, I then measure the DVA voltage at the primary wire to the coil. I will get a small length of #22 wire, strip it back, and wrap it around the primary post of the coil, then press the wire and boot back on. There you have a crude example of a back probe technique. I look for the correct DVA voltage at that point.

Now it gets a bit troublesome. Depends what I see at the coil primary as to what I do next. If low voltage, but not zero, I will suspect the stator charge coils (usually the brown pairs coming from the stator) and move directly there to measure the DVA voltage off of them. Good voltage there (input), but low at the coil primary (output), will point me to the pack.

If the DVA at the coil shows zero...then I suspect the timer base, because if it is not triggering the pack to fire, then the output at the coil would of course be zero. If timer base is triggering, then back to the pack.

I always try to substitute in a known good part, (swap coils for example), before replacing any electrical part. If you have good spark on #1 for example, then with a bit of work, you might be able to swap some wires in the connectors, to JUST USE #1s trigger output to drive the dead cylinder's PP input to see if it comes to life that way. This is just an example. Of course this is only for testing, as the engine would not run like this.

There is a definite art to debugging the failed ignition component. Hope some of this rambling helps you.

 

[Rick.]

Re: CDI ignition call for help/understanding

Thanks guys for the help. I'm having a hard time feeling encouraged about all this though. LOL. Is the OMC breakout box essential for trouble shooting or does it basically make the job easier? I only maintain my own motors and only three of them have CDI ignition so if possible I would avoid buying the breakout box. So a back probe is something you have to make on your own I take it? I do understand how it would get to the wire/voltage now. AlTn you've no idea how much less of an elec. tech I am than you which makes your comment really insulting!! I can see myself buying a DVA if my meter doesn't do the job. Do you fellas own DVA adapters that work with your digital multi's or do you have an analogue peak reading meter? Again, Thanks for the help. I will be printing your replies to keep in the back of my manual. Rick.

 

[daselbee]

Re: CDI ignition call for help/understanding

To answer two of your specific questions...no you do not have to have a breakout box, it just makes things easier when you are working on lots of motors, and yes, I usually fabricate some sort of probe to go in back of a connector that I want to backprobe.
There is also the wire insulation piercing solution, but I would paint the pierced hole with some sort of liquid neoprene if I had to do that.

 

[Rick.]

Re: CDI ignition call for help/understanding

Thanks. I really appreciate you taking time to help me along with some clarity to my confusion. Your answers are just what the doctor ordered. This is an issue I will be a lot happier learning thru the winter. Right now all I want is to get it running so I can fish. Rick.