Ignition Problems

[Chip_W]

Hi y'all. new member to this site and can't believe how much experience and information is here. A Big Thanks.

I was wondering if you can keep me from beating my noggin against the wall. I have a 91, 351, Prostar 190 that I bought a few years ago. I've used it with absolutely no issues until I decided to change the spark plugs a few weeks ago. Although I have the standard 240 hp 351, I messed up and bought the plugs for the 351 HO, Autolite 764. Not knowing I had the wrong plugs, I took the boat out over labor day weekend and it would start good, idle good at first, but as it warmed up it would begin to idle rough. In addition to the rough idle, there was a strong fuel smell, which indicated to me I was missing a cylinder. Knowing something was wrong when I got home I searched this site and found that I should have used the Autolite #24 plugs. Today I installed the #24 (gaped to .035), new plug wires, distributor cap, and rotor that I purchased from Skidim. Started the boat and it didn't fix the problem. Is there a possibility that I messed up the electronic ignition by running the wrong plugs? Could changing the plugs change the timing? I did change plug brands. The plugs I replaced were NGK. I checked the advance springs in the distributor and everything seems to be moving freely. Could I have messed up the coil?

[thatsmrmastercraft]

Welcome to Team Talk. Any chance you crossed a couple plug wires?

[Chip_W]

Thanks mr. mc for the quick reply.

I don't think so. To avoid that problem when I replaced the plugs and wires I did them one at a time. Just to make sure it's right though, I'll check it tomorrow.

Another thing I thought it could be is poor gas, but I've run new fuel through it and the problem remains.

[TCrate]

Check the plug wires to make sure you did not miss a connection. Also make sure you did not damage one when you swapped them out. You can determine which cylinder is not firing by starting the boat and idling it. Pull the plug wires one at a time. As you pull each one the motor should run rougher than with all 8 connected. After you check each wire reinstall it. The one that does not change the idle quality is the one that is not firing. Then check the resistance on the wire or that plug. It is possible you cracked the plug as well. Good Luck.

[Covi]

Check the plug wires to make sure you did not miss a connection. Also make sure you did not damage one when you swapped them out. You can determine which cylinder is not firing by starting the boat and idling it. Pull the plug wires one at a time. As you pull each one the motor should run rougher than with all 8 connected. After you check each wire reinstall it. The one that does not change the idle quality is the one that is not firing. Then check the resistance on the wire or that plug. It is possible you cracked the plug as well. Good Luck.

Dont use your fingers to do this you could get zapped.

[oldairboater]

I think you have a misfire. Check all of your plug connections including the distributor side and double check your firing order. It is possible that you broke or got a bad spark plug also. Doesn't happen often but it does happen.

[frosty]

Dont use your fingers to do this you could get zapped.

Zapped would be an understatement! :shocked:

[Chip_W]

I checked firing order and all is good. I then took a heavily insulated screw driver and checked spark to the plug by removing the plug wire from the plug, inserting the screwdriver into the wire end, starting the engine and checking for spark against the manifold. All cylinders have a spark. Oh, and yes, even though I had the big screwdriver I still got bit twice..zap, zap, zap.. I’d die being a snake handler. I then pulled each plug to see if they were wet. All had a flat chalky black color on the tip, but some were a little wet around the base. I really like Tcrate’s idea of pulling plug wires at idle. I tried this and it may sound crazy but I really couldn’t make out if pulling that wire made it run worse or not. Because I wasn’t brave enough to remove these while it was running, I removed them one at a time then started the engine and let it idle. Is it absolute that I pull them while it’s running? If so, I’ll have to find a tool like Covi suggests. I’m afraid pliers will destroy my new plug boots.

Even though there is a spark could it be that it’s a weak spark, an indicator of a bad coil, or ? I did notice when I pulled each wire to check for spark that it sounded like there was an internal clicking noise in the coil. Is that normal? Also, when I installed the plugs and plug wire there was this dielectric stuff in a tube that came with the wires. I put a small amount of this stuff on the plug tip. I hope that was the right place. Thanks everyone for the input! Wife and kids wanted to go skiing today, but…well let’s just say I’m in the doghouse.

[Laurel_Lake_Skier]

The dielectric grease should go on the boot. It is non-conductive and designed to add to the insulating ability and seal of the boot and the spark plug insulator. If you put the grease on the tip of the plug - I assume you are referring to the outside end not the tip that would be inside the cylinder - it may be enough to prevent a good connection between the plug and terminal.

[Chip_W]

yeah, I figured out that the grease went on the boot after I posted. It was on the outside end of the plug, but I've since cleaned it out with a q-tip and alcohol. Good and clean now, but the problem remains.

I went to the autoparts store this afternoon and bought one of those inline spark checker. It has a light in it that blinks as the cylinder fires. again, I have spark in all cylinders. I'm beginning to wonder if it's a spark related issue at all. How would this play into the problem - when I remove the hose from the PCV the engine runs much better? I can shake the PCV and feel the ball inside move freely back and forth, but the second I put it back on the hose it slows the engine, then I put it in the valve cover and it really starts to choke and send black smoke out the exhaust. There's another post on TT where Mr. MC suggests these symptoms are the result of a blown power valve. I’m beginning to wonder if it's a flooding problem?

[thatsmrmastercraft]

Your problems could be the result of a blown power valve. Often times a good backfire will cause it to blow. They can also fail just because of age and/or ethanol working on the rubber diaphragm. Any backfires when the wrong plugs were in?

[Chip_W]

It didn’t backfire, but when I replaced the plugs the first time I did monkey around with the linkage trying to lubricate it with some WD-40. I wonder if when I was moving the linkage by hand that I might have ruptured the power valve diaphragm. At this point that seems most likely to be problem. Is the power valve on the bottom of the front carb bowl? Would you suggest just replacing the power valve, or rebuilding the whole carb. I rebuilt the quadrajet in my pickup last year without problems. Are Holly’s harder or easier to rebuild? Thanks again for the help!

[thatsmrmastercraft]

The power valve is located inside the primary fuel bowl and is screwed into the main body of the carb. The linkage you were working with was for the secondary diaphragm. You couldn't have damaged that by lubricating and ensuring the linkage was moving freely.

Holley 4160 carbs are very easy to rebuild and work on. If you choose to rebuild, be sure to get a marine rebuild.

To test the power valve for function, you would need to remove it from the carb and try to turn the small end while holding the larger end. It should not turn. If it does, it means the diaphragm is bad. If you replace the power valve , replace with the same number valve. They are marked as to the vacuum level that they open. Typical power valve in a Inboard is 2.5 (vs. an automotive which might be a 6)

Another thing to consider when doing any carb work on a Holley is to upgrade to the Blur reusable bowl gaskets. The stock gaskets are only good for one time.

[Chip_W]

Ordered a carb rebuild kit from SkiDim today. I also threw in a coil, maybe a waste, but almost out of summer and I'd like to squeeze in a couple more ski days. Hopefully I'll get the order by the weekend. Will let you know how it works out.

[Cloaked]

Ordered a carb rebuild kit from SkiDim today. I also threw in a coil, maybe a waste, but almost out of summer and I'd like to squeeze in a couple more ski days. Hopefully I'll get the order by the weekend. Will let you know how it works out.
The instructions that come with the rebuild kit are a far cry from useful.

If I recall correctly, there is a good tutorial somewhere here, or on Holley's site which references an automobile application but it is almost step by step the same. A couple of hours (aside from the overnight soak if you so choose) is about what it should take. I think I spent maybe 3 hours with mine after a soak. One thing that helped me was having a good working space ready with a chair and a beverage.

I have a PDF of the same steps attached below.

Point is, do not expect a good set of instructions. Get some rounded up before the kit arrives. The process is easy enough, just takes a little time and patience.

http://www.holley.com/TechService/Library.asp



.

[Cloaked]

Holley Info

.

[Cloaked]

Adjust your air screws and your electric choke afterwards. You will now have a fresh set of gaskets and may need a little tweaking.

http://www.youtube.com/watch?v=2YCbkaXuqvE


You will not use all of the parts that come with the kit, so don't think you have left something off. There are parts in these kits for other similar applications.

Some of the steps in the tutorial can be skipped or considered not applicable. You be the judge of that. I ddi not do any vaccum tests, etc.



.

[Chip_W]

Wow, Cloaked, thanks for taking the time to post and share the info. The step-by-step detailed .pdf will be very useful. This may turn out to be a pretty fun project. appreciate ya.

[Chip_W]

Hey guys, I rec'd my new coil and I'm trying to install it. Problem is I'm not sure what wires go where. The old coil has "Bat" on one of the 3/8" terminals and nothing on the other. The new coil has "+" on one side and "-" on the other. The Bat side on the old coil has three purple wires attached to it where one goes to the choke, one to the distributor and one into a wiring harness. Will these three purple wires go to the positive side, or negative side of the new coil? Thanks!

[Cloaked]

Hey guys, I rec'd my new coil and I'm trying to install it. Problem is I'm not sure what wires go where. The old coil has "Bat" on one of the 3/8" terminals and nothing on the other. The new coil has "+" on one side and "-" on the other. The Bat side on the old coil has three purple wires attached to it where one goes to the choke, one to the distributor and one into a wiring harness. Will these three purple wires go to the positive side, or negative side of the new coil? Thanks!
See if this helps. I suspect the positive side, since one of the purple wires goes to the choke as a hot lead. The others should follow suit. I am not 100% on this but it seems like the diagram indicates such. Someone that is in the know may comment.

.

[TX.X-30 fan]

Wow, Cloaked, thanks for taking the time to post and share the info. The step-by-step detailed .pdf will be very useful. This may turn out to be a pretty fun project. appreciate ya.



He is a saint........................... :D

[Chip_W]

Coaked, the diagram worked perfect. After, new plugs, plug wires, cap, rotor, coil, gas, PCV valve, rebuilt carb, new transmission fluid (unrelated but had to be done), and help from y’all, the Prostar is purring like a kitten. It really made my night. It’s a little troubling that I can’t definitely pin the fix to a single component, but I have a strong suspicion that it was the carburetor spacer gaskets. When I removed the carb there were little wandering black veins that looked like leaks. The power valve in the carb was ok. Again, can’t say it enough, thanks for helping me work through this deal. Off to the lake tomorrow. :D

[Cloaked]

Cloaked, the diagram worked perfect. After, new plugs, plug wires, cap, rotor, coil, gas, PCV valve, rebuilt carb, new transmission fluid (unrelated but had to be done), and help from y’all, the Prostar is purring like a kitten. It really made my night. It’s a little troubling that I can’t definitely pin the fix to a single component, but I have a strong suspicion that it was the carburetor spacer gaskets. When I removed the carb there were little wandering black veins that looked like leaks. The power valve in the carb was ok. Again, can’t say it enough, thanks for helping me work through this deal. Off to the lake tomorrow. :DEnjoy the lake. Glad you got your boat running to satisfaction. Nothing like a high level of confidence in a smooth running engine. :)