No fire on 4, 5, 6.

[macgyver]

I have a 2001 Challenger 1800 with a M2 Mercury 240 EFI. Last weekend I put a hole in the hull and it lost power. I repaired the hole in the hull. I still have no power. Changed the plugs and checked the fuel system for water. Then I checked for spark... I have no spark on 4, 5, and 6. I moved the working coils to the nonworking and still have no spark on 4, 5, and 6, so that tells me the coils are good. Any suggestions what might have gotten wet to create this situation.

Thanks and have a good day!

 

[Dr Honda]

Welcome,


OK... its technically a 2-stroke... but the Merc engines have their own forum. (I'll move this for you)


Now... with your problem.... Losing spark on 4/5/6 is a strange combo. That means you lost the bottom starboard cyl... and the 2 bottom port cyl's. It would be more common to lose a bank.... like 2/4/6. (That would be all the port side cly's)

Are you sure about the cyl numbers? Port side is 2/4/6 and the starboard side would be 1/3/5.

 

[macgyver]

Yes IM sure of the cyl #. It has individual coils. And I exchanged the non working for the working and the 4, 5, and 6 still have no fire.

 

[Dr Honda]

OK....


The coils do balance each other... so the coils that are firing may actually be the bad ones. (if that makes sense) There is a diode, that creates a reverse current. OK... later tonight... I'll look at the flow diagram, and let you know. But... you should check each coil, using a meter, to see if one has an open on the diode. (do you have the Merc manual?)

 

[macgyver]

I dont have the manual.

 

[Dr Honda]

OK... I found it. (had a few min to look)

And yes... there can be a prob with 4/5/6. The high voltage charging is split... 1/2/3, and 4/5/6. So... coming from your Mag... look for a green/white wire... and a White/Green wire. These charge the coils. To start... just make sure they are clean and tight, on any of the connections. (and at each coil) Chances are... the wires are all OK since the your 1/2/3 coils are firing.


So... going from before... basically... there is a diode on the charge wires, within each coil pack. The output of the MAG is AC voltage. So... 3 coils charge in one direction... and 3 charge in the other. The diode acts as a gate, to allow the power to flow in only one direction.

Got that?


OK... so... if your 4/5/6 lost fire... they probably aren't charging. (the high voltage charges the capacitor, to make the spike in power for the spark) So... that means there is a short in a diode (or an open) in your 1/2/3 coils.


So... you need to check the 1,2, and 3 coil packs. Chances are... one of those three are bad.


So... looking at the manual... put a meter on the black and wht/grn wires, at the coil. You should have continuity in one direction, and an open in the other. Needless to say, you need to unplug the coil from the harness, and check the coil directly.

 

[macgyver]

I have a service manual for the ignition system now. I have tested all the circuits on all the cdm's per the specs in the manual 3 times... all appear to be good. I tested the stop diode circuit...forward and reverse. I tested the return ground circuit...forward and reverse. I tested the trigger imput and the secondary impedance. Now Im scratching my head...which way to go next? Also remember, that something may have gotten wet, because the loss of power happened when the engine compartment took on water...

 

[Coastiejoe]

How much water did you take on?

What components were submerged or likely submerged based on forward momentum?

 

[macgyver]

Got it running...runs great. It was a ground problem. Every ground is important!! Thanks Dr. Honda!!

 

[Dr Honda]

Glad we could help... but sounds like yo found it yourself.

Was it one of the grounds at a coil pack?