Cylinder Misfire

[Reel Poor]

Mercury 90 hp ELPTO 2003 Serial # OT617676

Compression #'s
#1 - 115
#2 - 115
#3 - 115

Spark Plugs Autolite 2872. Look new.

#1 cyl - no fire
#2 cyl - firing
#3 cyl - firing
Engine runs on #2 & #3 cylinder. Dead miss on #1.

Switched #1 & #2 coil positions.
#1 cyl - firing
#2 cyl - no fire
#3 cyl - no fire
Engine runs on #1 cylinder. Dead miss on #2 & #3.

Moved origional #1 coil to #3 cylinder and #3 coil to #1 cyl and origional #2 coil back to the #2 cylinder position.
#1 cyl - no fire
#2 cyl - firing
#3 cyl - firing
Engine again runs on #2 & #3 cylinder. Dead miss on #1.

WTH ? ? ?

 

[Laddies]

Re: Cylinder Misfire

Sound like #1 CDM (coil) is shorted

 

[Reel Poor]

Re: Cylinder Misfire

Sound like #1 CDM (coil) is shorted

Why would it fire when moved to the #3 cyl ?

 

[Laddies]

Re: Cylinder Misfire

The CDM ign. acts real strange at times, at times one CDM is shorted and it effects anouther cyl. I usally disconnect the units one at a time and ck for spark. the stator is apparently OK as you wouldn't have spark at all if it were bad and the trigger is working on all three so by the process of elemination I say CDM and would think #1. I have the advantage of a CDM tester from CDI which I would use but most don't so the best you could do would be OHM or volt test the stator and trigger before you buy the part-Bob

 

[Don S]

Re: Cylinder Misfire

This is from the manual RP, kind of explains what you were seeing.

3 Cyl.:
CDM #1 gets its charging ground path through CDM #2 or #3
CDM #2 and #3 get their charging ground path through CDM #1
A shorted Stop Diode in CDM #1 would prevent CDMs #2 and #3 from sparking.
A shorted Stop Diode in CDM #2 or #3 would prevent CDM #1 from sparking.

 

[Reel Poor]

Re: Cylinder Misfire

This is from the manual RP, kind of explains what you were seeing.

3 Cyl.:
A shorted Stop Diode in CDM #1 would prevent CDMs #2 and #3 from sparking.
A shorted Stop Diode in CDM #2 or #3 would prevent CDM #1 from sparking.

From this I would conclude that CDM #2 is shorted because origional complaint is no spark at cly #1, when I switch places with CDM 1 & 2 only cyl 1 fires, I lose cyl's 3 & 4.

Sounds like complicated simplicity.

Thanks Guys

 

[Don S]

Re: Cylinder Misfire

when I switch places with CDM 1 & 2 only cyl 1 fires, I lose cyl's 3 & 4.

Bet when you lost #4, you lost piston, cylinder and all, did't ya

Anyway, got an email address? I got something for you to read that is too big to put here. It's about 1.8MB.

 

[Reel Poor]

Re: Cylinder Misfire

Bet when you lost #4, you lost piston, cylinder and all, did't ya

Were keepig cyl #4 and all its accessories in the spare parts bag for emergencys.

 

[Don S]

Re: Cylinder Misfire

Got it, you can edit out your email address if you want.

 

[Don S]

Re: Cylinder Misfire

You have mail......

That ought to keep you busy for a couple of minutes anyway.

 

[Reel Poor]

Re: Cylinder Misfire

WOW.......Thanks for the literature. I think i'll go give her a complete examination.

Anybody seen my rubber gloves ?

 

[Reel Poor]

Re: Cylinder Misfire

Replaced the #2 CDM and she pured like a kitten.

Thanks