CDI Testing Procedure? 1995 Yamaha C85 TLRT

[JoLin]

I need a guru. Tracking an apparent ignition problem. Have resistance-tested the coils individually and they match the specs in the shop manual. I'm having trouble interpreting how to test the terminals in the CDI. I think I understand the 'grid' contained in the manual (resistance readings across various combinations of leads) but the manual is unclear on 2 points...

- Ignition On or Off during testing?

- 'Over-Rev' sensor lead remains connected or not?

So far, in testing each of the 3 coil leads to the 'W' connector (for example), I'm getting consistent readings of 55 ohms across all 3. The book calls for 75 ohms +/- 20% (or, 60-90 ohms). Might a failing CDI give 'out of range' but consistent readings across all? Confusing, and at $600 I don't want to guess.

(gotta tell you, compared to the OMC manual I had for a 1996 Johnson, Yamaha's shop manual is pretty poor)

Thanks.

 

[99yam40]

Re: CDI Testing Procedure? 1995 Yamaha C85 TLRT

do the peak voltage tests into and out of the CDI.
they are a lot better test than the ohm readings

Make sure you use a DVA adapter if you do not have the proper voltmeter for these systems

 

[JoLin]

Re: CDI Testing Procedure? 1995 Yamaha C85 TLRT

Thanks, guy, but I'd need you to describe those tests in excruciating detail. My genu-wine Yamaha service manual doesn't make a single mention of voltage in any component testing. It speaks only to resistance testing.

 

[99yam40]

Re: CDI Testing Procedure? 1995 Yamaha C85 TLRT

My genu-wine Yamaha service manual doesn't make a single mention of voltage in any component testing. It speaks only to resistance testing.

Seems you do not have a genu-wine Yamaha service manual then, where did you get that thing?

See if this will help some it is not from Yamaha, but has good info on troubleshooting
I believe Yamaha specs on page 112
ISSUU - CDI Electronics Practical Outboard Ignition Troubleshooting by CDI Electronics

 

[JoLin]

Re: CDI Testing Procedure? 1995 Yamaha C85 TLRT

Thanks for the link- mine IS the Yamaha factory service manual for my engine...

YAMAHA
CV85/C75/C85
Service Manual
LIT-18616-0044

Yamaha Motor Corporation USA
Printed in USA by Crestec USA

 

[JoLin]

Re: CDI Testing Procedure? 1995 Yamaha C85 TLRT

I found a downloadable version of the CDI Troubleshooting Guide here:

Technical Support | CDI Electronics

Looks like it'll be pretty handy. Once I've digested some of it, I'll probably have a few more questions concerning the troubleshooting procedures. Also have to either buy or borrow a DVA, so I'll be checking around to see if a nyone I know can lend me one.

Thanks for the guidance to this point. I'll be back!

 

[JoLin]

Re: CDI Testing Procedure? 1995 Yamaha C85 TLRT

Just following up. There were 2 running issues, but as it turned out neither had to do with the CDI. The first was bad fuel. I'll need to pull the tank and clean it out. Luckily it isn't a terrible job on my Sylvan. A portable tank and fresh fuel solved that issue. It still wasn't quite right, so I put an air gap spark tester (again) to each of the cylinders. This time #2 looked weak/erratic so I broke out the DVOM again.

Specs call for 4.8 ohms resistance +/- a fraction. 1 and 3 were within spec, but #2 read nearly 15 ohms. Replacing a cable means replacing the coil at nearly $100. Ouch. So, to be sure what I was dealing with, I stripped off the boot and spark plug connector (spring), then cut back the cable about 1/4". Put the DVOM to it and got a reading of 4.76. Bingo. I ordered a new boot and connector, replaced those and I was back in business for about $10. (replacement is a pain in the butt, btw).

I now have a rock-steady idle of 900 rpm (might be a little less) according to my dash-mounted tach. Cold or hot the motor fires immediately.