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L6 no fuel to cylinder

A

amxerhull

New member
My motor is a 1984 "tower of power" inline 6. It appears that #6 cylinder is not getting fuel as the spark plug looks brand new. Cylinder #5 which shares the carb with #6 looks like all the other plugs with normal amount of gas/oil on them. The carb for #5/#6 does not have separate jets for each cylinder. #6 has lots of spark and the compression is the same as the other 5 holes (140). I just bought the motor and have had only one short test run so I have no history to share with you. Where should I go from here?
 
Pull the powerhead off.-------Pull the lower bearing housing off.-----Inspect bottom seals and have a look at the reed valves.
 
I believe post #2 is clear on what needs to be done.-------I assume that the # 6 sparkplug was changed out and that it did not show water on the plug.
 
I just pulled #6 and could find no evidence of water. I turned the engine over to see if I could get any water out of the cylinder (I used the boat yesterday) and there was no evidence of water in the cylinder. As a side note, the motor starts instantly, idles great, and has more power than my boat needs, but this clean plug has me stumped and I don't want to hurt the engine.
 
If the lower seal is blown then basically you can suck exhaust into the crankcase along with water.----That is not good.------It also will not pull the correct amount of fresh fuel / oil into the crankcase.-Also not good.---------You can inspect the reed valves for #6 when lower bearing housing is out as well.------Not a good idea to keep running the motor as it is.
 
I tried to cut corners (sorry, it's a family trait I have inherited). My local marine mechanic suggested I replace the exhaust gaskets (3) because that could be the problem and I could do that without pulling the powerhead. I found evidence of water in the lower areas of the exhaust and thought I might get lucky but after testing it for about 1/2 hour, I pulled #6 plug and it still looked "steam cleaned". Oh well, at least I have new exhaust gaskets. Time to pull the powerhead and check the lower seal and reeds on #6!
 
Sorry, but on a 2 stroke engine you can not keep running / testing unless you are sure you are getting the proper amount of fuel ( and oil ) to all cylinders.----Too much risk of doing major damage.
 
I think I am ready to remove the 8 nuts that hold the motor to the housing but I can't see where to disconnect the shift linkage that disappears into the tube to the lower unit. This motor has a jet pump on it. Do I need to drop the jet pump to find the shift link connector?
 
No. There are two aluminum adapter/ exhaust plates below the power head. Be sure to split the PH from the top adapter, not between the two adapters, and you'll be okay.

Jeff
 
Thanks Jeff, I got the powerhead out and removed the lower end cap. The inner seal is torn so I will replace the end cap seals and O ring. The reed valves and lower bearing appear to be good. There is milky mess looking up into the muffler area so I may have to re-do my gasket work in that area or at least re-tighten all the water jacket cover bolts and exhaust cover bolts. The milky mess is very prevalent in the engine housing exhaust tubes and where the end cap resides.
 
The bearings on these motors are designed to stay on the crank, where the housing slides right off--nice design!

It helps to loosen the crankcase to block bolts nearest the housing, so the housing pulls out easier. When it's back together, retighten those bolts and don't worry about leakage--the "gaskets" are strips of cork that don't leak.

Jeff
 
Damn. I just got back from a test and #6 is still being washed. At this point I have replaced the lower seals (one was torn), all 3 of the exhaust gaskets and retorqued the exhaust plates. The reeds for #6 looked like new. All cylinders have 140 pounds of compression. What do I do next?
 
Check that the lower seals are in the right way around.If the bottom seal lip is facing the wrong way it will allow water ingress
 
haventaclue said:
Check that the lower seals are in the right way around.If the bottom seal lip is facing the wrong way it will allow water ingress
Click to expand...
I was very careful here. My manual said both of the lower seals should be installed with the lips of the seals facing toward the outside of the cylinder head.
 
Is the #6 sparkplug wire / boot shorting to the cover / cowlings ??------What does " lots of spark " mean here.--------To me lots of spark is spark that will jump a gap of 7/16" and that is the test that should be performed !---The water cover gasket does not cause an internal leak to the cylinder.
 
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If I have weak or no spark wouldn't the plug be covered with unburned fuel/oil (assuming the cylinder is not being washed)?
racerone said:
Is the #6 sparkplug wire / boot shorting to the cover / cowlings ??------What does " lots of spark " mean here.--------To me lots of spark is spark that will jump a gap of 7/16" and that is the test that should be performed !---The water cover gasket does not cause an internal leak to the cylinder.
Click to expand...
 
Why not do some simple testing to see what is going on with # 6.------Obviously you do not want to replace / swap a plug wire to find out.
 
I have appreciated your suggestions and I thought I asked a reasonable question. I don't want to sound ungrateful but I have raced and done mechanical work on cars for 54 years so I am relatively confident that I can gauge the quality of a spark. That being said, I have almost no experience with 2 stroke outboard repair so I still would appreciate your help.
 
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