1986 140HP no spark on 1 & 3

rude70

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Mar 6, 2006
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Hi I am working on my friends Yamaha 140AET0.

There is no spark on cylinders 1 & 3, but there is spark on 2 & 4.

I swapped the CDI 2 & 4 outputs and connected to coils 1 & 3 and there was spark - so coils must be ok

Is the issue likely to be the power pack or the trigger/pulse coils? I have down loaded the manual but was looking for a few pointers cos the power pack is $500!!

Thanks
 

99yam40

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Sep 7, 2008
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If you have the manual follow the testing procedures for ignition system.
Ohms and peak voltages from pulsar and charge coils and then outputs of CDI

If good inputs but no or bad outputs of CDI would be a problem with CDI if kill circuit is not grounding out the voltage
 
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rude70

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Update - sorry there was no spark on #1 & #2 cylinders - I checked out outboardignition.com but they do not ship to Australia! I ran some tests yesterday and the ohm readings were mid range in the specs for the charge coils and pulse coils. I was using a digital multimeter and could not get a reliable read on the voltages but I saw as high as 65v on the charge - have been told that I should use an analogue!. The output of the CDI pack on 1 & 2 was nothing and spark is stil on #3 cylinder - from the spark tester. I am inclidned to think it is the power pack since the ohm readings were good- would anyone agree?? Any further advice? thanks
 
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99yam40

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you need the proper test equipment
A DVA adapter with your DMV will work fine
 

rude70

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Mar 6, 2006
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Thanks 99yam40 I made a DVA with help from google! I tested the pulse coils at cranking speed looing for 2.5v but got about .5v. Similar results with charge coil and CDI out put to coils.The cranking speed seamed low (it's my friends engine) so I removed the spark plugs and of course cranking speed increased.Now all voltages in spec, pulse coils just over 3v, CDI output around 100v same with high speed charge coil. Low speed charge coil around 20+v. I am suspecting the starter motor because car jumper leads connected -ve to starter earth and postive to starter (bypassing solenoid) still had a slow cranking speed - battery was a fully charged 600cca marine battery! How can I test the starter motor? Thanks
 

rude70

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Mar 6, 2006
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Update new battery power cables fixed the starter motor issues. Still now output on cyl one from the cdi. Got a secondhand cdi, still not out put on cyl 1 - from spark tester ot from a peak DV. I understand that a change in polarity from the magnets changes the polarity of the output from the timer base that determines which of cyl fires. Is it possible that the timer base is the fault? Thanks
 
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