Merc won't fire on one side

[Damn Yankee]

I have a 1994 Mercury 135HP and the left side (cylindars 2,4,6, I believe) have no spark at low RPM. Out of the water I run the motor and it idles rough and imbalanced however in the water the motor idles rough however when I accelerate there is a noticable increase in power like the cylindars are kicking in. I have a shop manual and my preliminary thoughts are a switch box problem but I have to check both of them with a meter to be sure. Does anyone have any ideas or advice.

 

[tashasdaddy]

Re: Merc won't fire on one side

take an induction timing like with you , while running check the spark with the light. i agree sounds like switch box.

 

[Laddies]

Re: Merc won't fire on one side

It could also be a stator, whikle cking for spark swap the red+red/white and the blue+blue/white wires on the switch boxes if the spark changes side of the engine it's a stator not a box

 

[Damn Yankee]

Re: Merc won't fire on one side

Thanks guys for the advise. I switched red/blue wires between the boxes and the left bank still didn't fire, so I narrowed it down to the switch box as the likely culpret, not the stator. Due to the cost difference, this was welcome news for once! Prior to the swap however, I visually inspected the engine for broken or loose connections and discover my bottom voltage regulator suffered some kind of geo-thermal meltdown. The wire insulation had melted and the plastic casing had a huge hole melted into it. I'm assuming the voltage regulator suffered a catostrophic failure of some kind (maybe a charging problem) and then took out the switch box. Is this possible, or did the swith box break and then take out the VR? There is a problem somewhere and I'm nervous about replacing $300 worth of parts only to have it happen again in a few weeks. Any suggestions on what caused the issue with these components?

 

[DHPMARINE]

Re: Merc won't fire on one side

A lot of Merc V6's use one switch box to run two cylinders on one bank and one cylinder on the other bank.Vis-versa for the other switch box.

The stator has a low speed rating (test). And a high speed rating (test).

That could be where your problem lies.Follow your manual for the ohm tests on the stator before going too far.

And it 'could be' a stator plus a switch box.

DHP

 

[Damn Yankee]

Re: Merc won't fire on one side

Thanks for the advice. I swapped a switch box and VR from my #2 engine and now it runs well. I'll test the stator today like you suggested, and maybe that will shed some light on the problem. It makes sence that the stator may have a problem because when I was out on the water the engine would bog down and then kick in during acceleration.

 

[Damn Yankee]

Re: Merc won't fire on one side

Ok now I'm really frustrated. Last week when I was trouble shooting my #1 engine firing problem I swapped the switch box and voltage regulator from #2 and #1 ran just fine after that. Problem solved, right. Now after ordering the replacement parts I replaced parts on #2 (which were placed on #1 during trouble shooting) and now #2 won't start at all...no spark! I double checked the switch box wiring and it checks out. The engine ran perfectly before I removed the switch box and VR. All the original parts are back where they were before the trouble shooting began. The only thing I can think off is I did put battery power to #2 without either switch boxes and one VR installed in order to trim the motor up for transportation. Maybe I shorted something in the process?? What's the next step for trouble shooting #2 for the spark issue? If this Merc was a horse I'd shoot it!!!! Help please before I go crazy

 

[Capt Ken]

Re: Merc won't fire on one side

Connecting +12 won't cause that problem. Battery power does not connect in anyway to the CDI's. Check the black/yellow wire for a ground. That is the kill circuit and if there's a ground on it, it will kill the ignition. Also check to be sure your engine doesn't still have the mercury switch on the side that kills the engine if you tilt too high. They have a habit of shorting out.

 

[Damn Yankee]

Re: Merc won't fire on one side

Thanks Ken. I just got your reply and I'm happy to say I found the issue. It appears the bullet connector on the idle stabilizer wasn't completely seated. The manual said to disconnect it to isolate it and recheck for spark. I disconnected it and it fired right up. Just for grins I inspected the bullet connector and I think it was corroded enough to cause a short. I clean it up and reconnected it and the engine runs great. Looks like between you guys and the manual, I saved a few hundred bucks...again Thanks a million, Scott