Help - Arcing / Sparking in the engine bay

[mira4581]

Hi all, I have a 2013 Bayliner with 3.0 Mercruiser MPI motor that's idling very ruff. Once its pass 1000 rmp the boat runs perfect. After suggestion from a friend I run the motor in the dark and saw arcing/sparkling all over the engine in different parts (top, side, bottom) every 2-3 seconds. I've been trying to address this idle issue for about a year now but never noticed arcing until this week and now thinking back i've heard the clicking/arcing noise for a while so it must have been arcing the entire time since my idle issue started. I've changed a few things: spark plugs (3 times), idle control valve (twice), distributor cap, rotor, spark plug wires , MAP sensor, O2 sensors, cleaned injectors. When I changed the spark plug cables I noticed the main cable which goes from the center cap to the coil was pretty dark on the coil side, but changing the cables didn't resolve the issue. My battery cables look great without any corrosion on the battery side, gas is not an issue. I am thinking the next step is to change the coil. Is it perhaps some negative/ground cable that's attached to the motor that's bad and causing the arcing ? I am at a complete loss at this point. I would appreciate any suggestions.

 

[alldodge]

Arcing all over the motor is different.
Is the motor clean, or wet?

 

[Grub54891]

What brand of plug wires. You can't go cheap on them. They are always damp till the motor warms up. Seen that happen more than once.....

 

[mira4581]

Arcing all over the motor is different.
Is the motor clean, or wet?

The motor is clean. What I mean it’s arcing in different spots not in one particular. The easiest for me to spot is when it’s happening between the belt and the engine block in the front.

 

[mira4581]

What brand of plug wires. You can't go cheap on them. They are always damp till the motor warms up. Seen that happen more than once.....

I don’t recall the brand but I am on my 3rd set , I’ve taken it to a few mechanics and that’s the first thing they do is replace the plugs. Unfortunately I didn’t notice the arcing and the mechanics did not either so I think if they knew it was arcing maybe they would have look at the situation differently.

 

[alldodge]

belt and the engine block in the front.

Up by the water pump?
If so, check your battery cable ground and other grounds attached to the rear of the block

 

[Grub54891]

I'd go to the coil as you stated it's black on top. Carbon tracking would do that. You said the mechanics change the plugs three times? Don't use champion plugs, it's a Chevy block, from my experience Chevy don't like champ's.

 

[alldodge]

Its not the plugs

 

[mira4581]

Up by the water pump?
If so, check your battery cable ground and other grounds attached to the rear of the block

Yes around that area, I checked all the ground cables that I could find and everything seems to be fine.

 

[mira4581]

The coil looks a little rusty but doesn’t seem to abnormal , I order a new coil anyway should be here at on Tuesday

 

[mira4581]

When I removed the distributor rotor it looked rusty to me ... is that normal ?

 

[alldodge]

Lots of rust, must be near or on salt water
Agree, think I would replace the coil also

The post does rust up if unprotected. Put a thin coat of grease on it after taking a small wire brush to it

 

[Grub54891]

Also, use dielectric grease on the spark plug wires and dizzy ends if you haven't already.