Dead cylinder??

[RCSConstruction]

Have the boat in for new cables and such and the mechanic just called and said I am not getting spark in number 6!! Claims the spark plug is all wet with gas.
At idle it will start to "load up" and you have to give it some RPM's to clear it out.
If I had a DEAD cylinder wouldn't the idle be terrible? My only complaint was a "dead" spot when launching really hard to get onto plane.
All the plugs show signs of being rich, so I am hoping it's just a fouled plug?
I have never seen a motor idle so good with a dead cylinder. Has the slightest miss every once in awhile but not the pop-pop-pop you would normally get with a dead hole.
Any advice? If I have been running on 7cyl's all along wouldn't my boat run like crap? I am pretty sure I would have noticed a dead hole..
Completely stressed now as I just put a new motor in last season and closed cooling system.
The carb is a marine 4bbl edelbrock. The motor is a 5.7l vortec.
The boat listed below.

 

[Robj]

Re: Dead cylinder??

If you are not getting spark at the cylinder, then it is an ignition problem which could be wires, plugs etc. I am sure Don has a checklist for this. It should be an easy fix, don't get stressed out about this one.

I think the symptoms you are describing could be due to a dead cylinder, especially with a V8. If it was a 4 banger the symptoms would be much more noticeable.

Have a great day,

Rob.

 

[RCSConstruction]

Re: Dead cylinder??

Would a spark plug fire and ignite any fuel if there was no compression?
Kinda irks me that he calls to let me know about a possible dead cylinder without throwing a compression tester on it.
So were looking at rings,valve stuck or head gasket? (if it's not electrical)
Sure seems to me that I would have noticed something like that.
Really weird.
Thanks for you reply

 

[QC]

Re: Dead cylinder??

Have him do a compression check? What's the big deal? Don't get stressed until you have all of the info . . . Definitely don't change any parts without all of the info.

 

[Don S]

Re: Dead cylinder??

mechanic just called and said I am not getting spark in number 6!!

If there is no spark, it's not going to fire that cylinder.
It's either a bad spark plug or a bad wire. That will cause no spark on one cylinder.
Shouldn't be a big deal, replace the part that isn't firing.

 

[RCSConstruction]

Re: Dead cylinder??

Thanks for the replies guys.
I guess you can sense how tense I am about it. If you remember last season I was doing nothing but working on this beast!
What got me shook up was he went over common issues, ignition,plugs,etcc.. and he really eluded to the fact it was mechanical. Also forgot to add that it smokes a little while idling and when I asked "is it oil?" he claimed he didn't know. I became very alarmed at that point because an out of tune motor's smoke is different than an oil burning one. Seemed like he didn't want to give me bad news quite yet.
I'll let ya know what I find out but the suspense is killing me. I feel like just going and picking it up and finding out myself. All I needed was a shift cable....lol:redface:

 

[Limited-Time]

Re: Dead cylinder??

Black smoke= an over rich condition. Blueish white smoke= oil. Generally speaking. And as stated before a compression test will rule out any mech. issues.

 

[RCSConstruction]

Re: Dead cylinder??

140-150 psi in all BUT number 6!!! Getting nothing at all.
Oil in the cylinder didn't change reading so I guess that makes it a valve issue.
So, So mad. I have owned more smallblocks than I can count and never had one run so good with a dead cylinder. Mind boggling.
Hoping it turns out to be a bad adjusted valve but I have a feeling a valve is stuck.
Better than a dropped valve I guess eh??

 

[Bondo]

Re: Dead cylinder??

Ayuh,......

Water in an exhaust port will Rust'em Solid in No Time.......

Good Luck.......

 

[Don S]

Re: Dead cylinder??

I have customers all the time tell me how great there engine is running, only to listen to it and tell them it has a miss.
One guy about 2 years ago told me his idled perfect, but seemed to lack some power. It was a 5.0L Mercruiser with EFI. My boss went out and started the boat and took it to the ramp to get it out of the water. He said it sounded like it had a dead hole.
I did a compression check, and sure enough. No compression in #8.
Pulled the head, and here is what I see. Notice anything missing????
No noise noted by the owner or the boss when he took it to the ramp.
I still am amazed it kept running and didn't knock or lock up.

 

[Coors]

Re: Dead cylinder??

LOL, no noise, even when the piston was breaking into small pieces?

 

[JustJason]

Re: Dead cylinder??

Wow... what was the deal on that one??? High speed high RPM hydrolock that the conrod pushed itself through?

 

[Don S]

Re: Dead cylinder??

Actually it was a brand new engine on a Bayliner 22. It had no indication of water in the engine or manifolds/risers at all. Salt water boat, so it would have at least left a few streaks.
Merc sent a brand new engine, the old one had about 40 hours on it. They also wanted the engine back before we took anything else apart on it. They really wanted to check it out and find out what happened. Even the Merc reps couldn't believe the pictures. Never did hear back from them.

PS: The compression test I did as after seeiing the spark plug all beat to death. And only consisted of my finger over the hole. Amazingly, the rod and wrist pin built very little compression. Even with the ring/s

 

[JustJason]

Re: Dead cylinder??

Amazingly, the rod and wrist pin built very little compression. Even with the ring/s

You must have been feeling crankcase pules from the downstroke of other pistons....
If there was no water the cylinder, it must have went out of round/taper or the piston/rings were never fitted correctly from the get go.... or a defective piston... woulda thought for sure there would have been water in that one.... oh well...

 

[TilliamWe]

Re: Dead cylinder??

RCS, have you had any issues with this engine "lugging" or failing to reach the WOT RPM range? If so, you have overheated the combustion chamber and "tulipped" a valve.
Remove that rocker arm cover if you can. Adjust the valves on that cylinder and recheck compression. I'll bet you'll get a little compression. When you do, pull the heads and have them reconditioned. If you have one dead cylinder, you 'll most likely have other bad valves.
A local machine shop charged me $160 to recon my head with valves they took from my other head, which had a crack. I paid $179 for a recon head from them.

 

[Don S]

Re: Dead cylinder??

I think all you guys missed his first sentence of the original post.

Have the boat in for new cables and such and the mechanic just called and said I am not getting spark in number 6!!

Compression does not make spark ....... the ignition system does.

 

[JustJason]

Re: Dead cylinder??

if he had no compression he'd have GREAT spark!!! the coil wouldn't even break a sweat.

 

[TilliamWe]

Re: Dead cylinder??

I think all you guys missed his first sentence of the original post.



Compression does not make spark ....... the ignition system does.

I didn't miss that at all. You all covered the reasons for no spark. I was addressing the posible cause of "no compression", which he also has. So he has no spark on the same cylinder that he has no compression.

Is there any possibility that the mechanic said he had "no fire" in #6?
He could have two unrelated issues on #6 or two related issues. Either way he has two issues, according to the info provided.

 

[bomar76]

Re: Dead cylinder??

I think the first thing he needs is another mechanic....if this one is baffled by no spark he is a lost cause.

 

[Fishermark]

Re: Dead cylinder??

Before you condemn the mechanic, re-read all the posts from the original poster. This gives us a good timeline of what the mechanic did and/or said:

"the mechanic just called and said I am not getting spark in number 6!! Claims the spark plug is all wet with gas...."

"he went over common issues, ignition,plugs,etcc.. and he really eluded to the fact it was mechanical...."

"140-150 psi in all BUT number 6"

Sounds like the mechanic did in fact check the basic causes of "a wet plug." Then proceeded to rule them out one at a time.