Sears Craftsman II stopped firing on one cylinder
- Thread starter vg066833
- Start date
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Maybe just slow down a bit and clarify some things. You stated that there was fuel in the oil and one cylinder didn't seem to be firing. The fuel pump idea was floated as they do fail on these. Or was it that there was fuel in the oil as one cylinder hadn't been firing. Or it has been cranked on for a long time. You mentioned checking the pump and installing a new coil. Did you and what happened? <--- These things are much more likely than a failed cam or one that somehow came out of time. You mentioned that the valves were working. If it gives to peace of mind, do a compression test.
grsthegreat
Super Star Member
Did you verify both plugs are firing with an inline spark tester?
Installed new coil, no difference. As far as determining that it was not firing on both cylinders, two ways to check. First unplug spark plug wire on cylinder not firing, engine still runs on runs on the other cylinder. Plug that spark plug back in and unplug the other one, engine wont run. The other way to determine engine not running on a cylinder is exhaust header pipe never gets hot compared to the other cylinder. Usually never had to crank my engine for more than about 10 seconds.
Topzide
Platinum Member
Need to check compression on down cylinder. Could be rings, valves or scouring on the cylinder walls. How many hours on motor? If near the 1000 hr mark, could be DOA. You've been through carb and pump, say you have spark? If no spark on just that one side, you need to trace the grounding lead to that side coil. As they say, spark, fuel and compression, it'll run!
grsthegreat
Super Star Member
i always use a cheap inline visual spark tester. the mags could be firing, but there may be other issues within that cylinder. i always run either a compression test or i run a cylinder leak down test.
OK compression check on both cylinders are: high side 92/low side 90. Manual for the Kohler engine says if it is less than 90 than I have an issue, but both are ok. The fuel pump is a different story. Removed the fuel pump from side of engine above the down cylinder. With some fuel still in the line and holding this line up so fuel would leak out of it, I moved the fuel pump actuator and fuel came out around the actuator. So new fuel pump is on the way. Did not that my oil level and slightly increased and smells like gas again. Although the oil level is not above the max fill line. Would this keep it from running even though there was fuel pressure at the carburetor when I took that line off?
Topzide
Platinum Member
If you have gas leaking into the crank case, this will wash out the cylinders and the you're looking at major overhaul or new engine! There's something that is not allowing the coil to fire on that one side. You know fuel is getting into intake since runs on one side, this could account for the fuel in sump. Only other thing to check is push rod on intake valve, if thats not opening to let fuel in, although you say that compression is good. Keep us posted and we'll figure it out.
Topzide
Platinum Member
Do you know the hours? Sounds like you need to do a cylinder leak down test. You seem to have all the other components for it to run. By doing leak down, you'll confirm that the compression release valve isn't stuck open. It'll still read on compression gauge but not have back pressure to run. Harbor Freight has a leak down tester.