Flywheel Trigger Magnet testing???

[vrundquist]

Hello all,

This is a followup thread to on I posted about a week ago. I have a 1999 Mercury 90 HP. It had a lot of problems. I am convinced that it overheated on the #1 cylinder. here is whai I know about the motor.

After warm up it has a very erratic spark on #1 all the time. #2 has intermittant erratic spark and #3 seems OK. I know this by using a timing light with a built in tachometer. On #1 I get readings from 5000 to 7000 at idle. On #2 the display just blinks (not sure what that means). #3 gives the correct reading.

When I first got the motor it did not run at all. Here is what I did to get some spark, and fuel to the motor.

New stator (old one had wires melted together), Sierra brand
New timer base (CDI brand)
3 new coils (CDI brand)
New voltage regulator (old one charging at 16.5 volts) Sierra brand
Rebuilt carbs
Rebuilt fuel pump
New upper seal to fix vacuum issue on #1
New Spark plugs

The only component that remains in the ignition system is the flywheel. Visually all themagnets look fine. Is there any kind of test to see if the trigger magnets are broken. They are encased in rubber (or maybe plastic...)

thanks,

victor

 

[Faztbullet]

Re: Flywheel Trigger Magnet testing???

Sounds like the bias circuit in pack is damaged, this is where trigger blk wire is attached to blk/wht terminal on pack. The trigger magnet is actually 3 magnets 120? apart, so it any where damaged it would affect all cylinders not just 1 or 2 cylinders due to the broken magnet would have to pass all coils on trigger.

 

[vrundquist]

Re: Flywheel Trigger Magnet testing???

this engine does not have a pack. the trigger coil is connected directly to the 3 coils. All 3 coils are brand new from CDI. Maybe I got a bad (1 or 2) from CDI.... I attached a wiring diagram for reference.

 

[j_martin]

Re: Flywheel Trigger Magnet testing???

Actually, there are only 2 magnets, and 3 coils in the trigger. Same thing on a V6, only they use both ends of the coils. The trigger magnets are in the hub part of the flywheel.

Leakage to ground on the kill circuit (black/yellow) could cause this trouble.

If you're making observations during engine cranking, slow cranking would cause trouble.

You can test trigger and stator output with a DVA.

hope it helps
John

 

[vrundquist]

Re: Flywheel Trigger Magnet testing???

I have tested all of the above. Only test I have not performed is the DVA test after the engine has warmed up. I found a new (used actually) on eBay. Hopefully that solves it!

 

[vrundquist]

Re: Flywheel Trigger Magnet testing???

and the tests are all fine. I also did all of the OHM tests on the stator and trigger coils.

 

[jeffersondodson561]

Re: Flywheel Trigger Magnet testing???

Where did you get that diagram? I noticed the CDM's all have a charge path from the stator. I thought that Mercury CDM's had a blocking diode and had shared charging path's thru a certain cylinder. Wondering if this diagram is from CDI Technologies showing their stator?

 

[vrundquist]

Re: Flywheel Trigger Magnet testing???

View attachment engine wiring diagram 17.pdfthat diagram is from seloconline.com, and it corresponds to the Merc factory manual as well.
attached is diagram from Merc manual. it says it is for a 1998, but the 1999 is identical.

 

[jeffersondodson561]

Re: Flywheel Trigger Magnet testing???

On #1 I get readings from 5000 to 7000 at idle. On #2 the display just blinks (not sure what that means). #3 gives the correct reading.

Try reversing the clamp on your timing light and make sure that the 2 cycle selector is always highlighted. Try and watch the flashes on the timing light to try and see if you can see the miss instead of reading the RPM's.

 

[vrundquist]

Re: Flywheel Trigger Magnet testing???

I did not try reversing the clamp, but I did view the timing light and it most definitely looked odd. The marks did line up, but it looked fuzzy, which told me that there was a firing issue...

I did have the 2/4 cyc selector on 2 cyl. I am going to put on a flywheel I purchased from ebay today. Will report back as to the status...

thanks,

victor

 

[fmeroney]

Re: Flywheel Trigger Magnet testing???

whats your outcome? Im having similar issues?

 

[Big flop]

Re: Flywheel Trigger Magnet testing???

STB side hidden down low does it
have a RPM limiter?