2012 8.1 #6 cylinder missing

zaayer

Seaman Apprentice
Joined
Jul 24, 2022
Messages
31
While my family was on vacation, I started feeling a mis. I could feel a shake at 1000-1200 rpms. I took the boat to a Volvo Certified mechanic. He hooked it up to a computer and said that #6 cylinder was missing. He swapped spark plugs and that had no effect. He checked for spark and said there was one. He thought that it was a wiring issue, but since I was 500 miles from home I would need to get it fixed at home.
The engine has 185 hours on it, but a drip from the engine hatch falls right above the #6 cylinder. I noticed that the coil pack 6 was quite rusted. When I pulled it off, the metal ring flaked and some rings from the coil broke off. I decided to replace the 4 coils on that side of the engine as the other 4 had no rust. That did not help. Still the shake. It seems to be getting worse with time.
My problem is that I have another vacation booked at a lake house in 12 days and no boat. I have ordered a new wiring harness for the starboard coil packs but they don't get here until Monday. I am also trying to find a mechanic local but they are all busy. Do you have any ideas on what to check on next?
The mechanic I met did not think it was a injector issue as the computer did not have any codes for the injector.
Also when I took off the exaust manifold #6 looked wet. I thought it was just unburnt fuel making it look that way. Maybe it is water?
Any ideas would be greatly appreciated. I don't want to cancel my familys vacation. My boys would be devistated.
Brian
 

dubs283

Vice Admiral
Joined
Jul 27, 2005
Messages
5,322
Cylinder drop test? Compression test?

A kv meter will show you a comparison of voltage through the plug wires.

What do the spark plugs look like?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,054
Check compression on 6 and a couple others to compare
 

zaayer

Seaman Apprentice
Joined
Jul 24, 2022
Messages
31
Cylinder drop test? Compression test?

A kv meter will show you a comparison of voltage through the plug wires.

What do the spark plugs look like?
The spark plugs look good. No fouling. I will check the plug wires. I have a new coil wiring harness. The mechanic thought the problem was electrical and possible in the harness. If that does not work, I am trying a compression test next. I really appreciate your help.
 

zaayer

Seaman Apprentice
Joined
Jul 24, 2022
Messages
31
Thank you both. I found the problem. It was a bad plug wire. I believe the malfunctioning coil caused the wire to fail. We Will Have A Boat On Vacation. I appreciate your help!!!!!!!
 
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