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View Full Version : Repeatedly fouled spark plug, 01 X9


CruisinGA
11-27-2012, 12:13 PM
http://img.tapatalk.com/d/12/11/28/ebuvu6an.jpg
While winterizing, I noticed the number 8 plug on my '01 X9 with LTR 330 engine looked very different than all the rest.
I noticed the same thing last year but didn't think much of it. I change my plugs every year with NGK. Two years in a row makes me a little concerned. See pic below.

CantRepeat
11-27-2012, 12:37 PM
Did you check for spark on that plug wire? Maybe the wire is going bad or grounding out on the exhaust manifold?

CruisinGA
11-29-2012, 08:04 AM
I suppose an intermittent problem is possible, but I know it has spark because the engine is definitely running on 8 cylinders. I have experienced only 7 cylinders (bag sparkplug) with this boat and it runs far better than that.

02ProstarSammyD
11-29-2012, 08:53 AM
I had a very similar situation granted it was with a merc ski but familiar none the less. Talked to my mechanic buddy and he insisted that it was cold starting and numerous restarts before the engine was warmed up. Fouled 2x in one season and watched my restarts until warm and haven't had the problem since. Could be completely unrelated

nm just saw it was one plug only. weird

JimN
11-29-2012, 09:35 AM
I had a very similar situation granted it was with a merc ski but familiar none the less. Talked to my mechanic buddy and he insisted that it was cold starting and numerous restarts before the engine was warmed up. Fouled 2x in one season and watched my restarts until warm and haven't had the problem since. Could be completely unrelated

nm just saw it was one plug only. weird

Have you checked compression/leak-down? How old are the plug wires? Check spark intensity.

Have you thought of using injector cleaner? 3M has a can that connects to the Shrader valve and you start the engine, running it on the can (pull the fuel pump fuse, IIRC). When it stops running, it's done. Let it sit for a few minutes, re-insert the fuse and it should be done.

Why NGK instead of MR43LTS?

JimN
11-29-2012, 09:38 AM
I suppose an intermittent problem is possible, but I know it has spark because the engine is definitely running on 8 cylinders. I have experienced only 7 cylinders (bag sparkplug) with this boat and it runs far better than that.

How it runs on 7 depends on which plug it is. Also, these use "waste spark", which means each coil pack fires both cylinders every time and if the plug wire, coil pack or IC module/connection to the IC Module is bad, you could see this kind of problem.

CruisinGA
11-29-2012, 02:28 PM
Jim,
Thanks for the response.

-I have been using NGK out of habit because all of my other toys/vehicles are Japanese and from my experience and understanding, NGK is a quality plug. Do you think I should switch to Delco on the boat?

-I have not done a compression test. I will take my tester with me next time I go to the lake. I do not have a leak down tester, but I suppose I could whip one up.

-I have considered a leaky fuel injector as a possibility, but I have not done the cleaner.

-Plug wires appear to be original. They look very good, but I have not tested resistance.

-I never would have guessed that how an engine runs missing a cylinder would depend on which cylinder?

I suppose the appropriate plan of attack might be-
1) Do the fuel injector cleaner just 'cause
3) Check spark intensity, if no issues-
2) Compression test for rings, leak test for valves, if no issues-
3) Check or replace plug wires
4) remove injectors for ultrasonic cleaning and flow testing

JimN
11-29-2012, 02:35 PM
Jim,
Thanks for the response.

-I have been using NGK out of habit because all of my other toys/vehicles are Japanese and from my experience and understanding, NGK is a quality plug. Do you think I should switch to Delco on the boat?

-I have not done a compression test. I will take my tester with me next time I go to the lake. I do not have a leak down tester, but I suppose I could whip one up.

-I have considered a leaky fuel injector as a possibility, but I have not done the cleaner.

-Plug wires appear to be original. They look very good, but I have not tested resistance.

-I never would have guessed that how an engine runs missing a cylinder would depend on which cylinder?

I suppose the appropriate plan of attack might be-
1) Do the fuel injector cleaner just 'cause
3) Check spark intensity, if no issues-
2) Compression test for rings, leak test for valves, if no issues-
3) Check or replace plug wires
4) remove injectors for ultrasonic cleaning and flow testing

You mean "switch back to", right? It came with MR43LTS from the factory and tehy work. Some parts stores don't want to carry them, but they're still available.

Doing a continuity test on a spark plug is like making sure a high frequency conductor will pass DC- it doesn't matter. The real issues come when plug wire can't pass impulses, which is what passes through spark plug wires.

Do the compression/leak down tests dry and at normal operating temperature, not with the fuel pump on.