99 PX150TLRX No Fire

[TexasHonda]

I am trying to resuscitate a 150 HP marine engine that has set up for several years after cylinder heads were pulled/reinstalled.

Tested Stop Circuit (OK no ground present at white wire to Control Unit w/ switch On). Pulling lanyard safety switch grounds white wire, however turning ignition switch to OFF gives 66 ohms resistance to ground.

Tested Ignition Charge Coils and got over 85V peak voltage on oscilloscope w/ spark plug leads shorted to ground and engine cranking over.

Tested two of six pulser coils (difficult to backprobe harness behind fuel vapor separation cannister) and got more than 2.5V w/ engine cranking and spark plug leads grounded. All tested about same resiistance from CU harness connector.

Tested Crankshaft Position Sensor output w/ engine cranking and got over 0.5V output.

Tested CDI/CU output four of the spark coils and got practically 0V while cranking engine and spark plug leads grounded.

Connected noid light w/ LED to Blu stranded lead and terminating Yel/Red at connector on Fuel Pump Harness and got one ~2 sec On flash then Off when keyswitch turned to On. I did not try to simulate a defect code to confirm I have interrogated CU correctly.

From the Clymer manual (Yamaha 115-250 HP, 1999-2002 Shop Manual) I'm using, it looks to me to be a faulty CDI/CU unit, but they caution this is relatively rare and to look for other faults. I have repeated testing twice w/ same results.

Question: What else could I test to confirm CDI is faulty?

thanks

[rodbolt17]

did you try a simple SPARK test?
does the HP pump run for about 3 seconds at key on?

[TexasHonda]

Yes, I did try spark tests w/ no spark. I got a spark indication (timing light flash) for a few secs first time I turned engine over, but nothing since.

Fuel pump clicks but does not run. I plan to address that after I get spark.

thanks

[TexasHonda]

Further testing of ignition switch shows intermittent resistance in Off position of near zero to 1Kohms. Changes when switch is wiggled.

I did not find any evidence of grounding of white stop wire when switch was wiggled in On position or switched from Off-On to support this as reason for no spark.

thanks

[rodbolt17]

using a DVA adapter or a peak reading NOT true RMS reading meter test both loaded and unloaded both the stator output and the pulser coil outputs.
you can use paper clips to back probe the connectors.
pulsers should have 3v cranking loaded or unloaded.
stator charge coil should have 85v unloaded and 110v loaded when cranking.
an oscilloscope, with the proper attenuator as nessasary, will show peak voltage.

[TexasHonda]

I used an oscilloscope to assess voltage levels. I'm reasonably confident the minimums were met, except for spark coils.

I will get a multimeter w/ peak voltage capture and repeat tests.

thanks

[rodbolt17]

an oscilloscope can capture voltage peaks.

some will require an attenuator to prevent over voltage damage to the scope.

[99yam40]

I will get a multimeter w/ peak voltage capture and repeat tests.
thanks

The Fluke meters and probably others that have peak hold will not work for this. You need a special one built for the ignition systems or the DVA adapter.

You would be better off getting a DVA adapter to use with your regular DMM unless you plan on using the special meter a lot.

[TexasHonda]

When measuring CDI voltage output to the spark coils, the Clymer manuals says to set multimeter for AC voltage measurement, however the system (CDI/CU) description describes this output as DC current to the coil ("The CDI unit or engine control unit converts alternating current to direct current and stores the current from the ignition charge coil, then releases the charge to the correct ignition coil using input from the pulser coil and/or crankshaft position sensor."). This makes sense; coil is charged DC volts then opened to generate spark.

I have been using AC setup on oscilloscope and getting a flat zero line. Is this possibly wrong?

thanks

[99yam40]

The Yamaha service manuals usually tell you to put peak reading meter on DC to measure the peak voltage out puts of charge coils, lighting coils,, pulser coils, and the out put of CDI to ignition coils or use a DVA adapter or proper peak reading mter made for these igition systems. Never tried a scope ,so have nothing to say about that.

CDI stands for Capacitor Discharge Ignition, it just stores the DC voltage in a capacitor( cannot store AC in a cap) and then discharges to ignition coils when told to. I am fairly sure they can not have the DC on them and then break connection if that is what you are saying.

Not all motors use a CDI system, so always make sure of what motor you are working on and the ignition system it has.

DVA adapter do not cost much and are easy to make if you can find the proper capacitor. the diode and resister are common.
the reading you get this way can easily be compared to the spec in manual

[TexasHonda]

Thanks, I tried DC setup on oscilloscope and got same results. I will get a DVA adapter.

[TexasHonda]

I have found what appears to be an anamoly, but I'm not sure.

The CDI/CU unit foundation has a ground point for the port side ignition coil harness. However when I measure resistance between engine ground and CDI/CU foundation I get 5 Mohms, a very high resistance. Circuit diagrams show only a single common ground.

It appears to me the CDI/CU foundation frame is designed to electrically isolate from the engine block. Rubber bushings between engine and foundation. This would imply I need a ground strap between the CDI/CU foundation and engine block, however there was nothing like this in my parts.

I have three ground leads from top side of CDI/CU unit. Two are connected to engine ground and one (port side ignition coil harness) is connected to CDI/CU foundation.

thanks

[TexasHonda]

I decided to remove the CDI/CU output leads and carefully go over the ground connections.

I found that the starboard side ground lead which originates from the starboard side ignition harness from CDI/CU was routed to engine ground and should have been attached to starboard side of CDI/CU mount frame (isolated from engine ground). This was somewhat speculation as Clymer manual does not show ground routings w/ any precision.

After reinstalling, I attempted to measure CDI output to ignition coils w/ oscilloscope (no DVA yet) and got nothing.

I removed the grounding lines to all the spark plug lead, and checked spark w/ timing light inductive pickup. Fire on all six plug leads!

Thanks for help and guidance.

Now to solve no fuel pressure

Regards