Johnson 5.5 CD-13 carb issue.

[joshadurham]

My compression is 90 psi on both cylinders. fuel/oil was the second tank run this season. ethanol free/24:1 fresh. and I did take out the filter, and it seemed to run better, Just not as smooth as usual, and wont run good at all at slow idle. The pressure tank releases alot of pressure when the lid is loosened, and the lines are brand new as of yesterday. I’ll troubleshoot the ignition system next. Thanks!

[fleetwin]

Not that I feel this is your issue, but please use 16:1 fuel/oil mix for that engine. I know, today’s oils are much better, etc, etc. But, those engines still use plain bushing on the big end of the connecting rods, and they will spit out a connecting rod if not lubed liberally.
OK, so compression is great, the tank is developing pressure, and removing the filter didn’t help much.
At this point, I’m "guessing" you are losing spark on one cylinder when you run slow. Have you tried new/different plugs? You may consider buying a few of those "inline neon testers", inexpensive and available at most auto parts stores (Harbor Freight as well). You can run the engine at the dock while watching the neon testers watching for a weak/intermittent glow. Keep in mind that a bad plug will affect the testers as well. Just be careful when using the testers, you don’t want to introduce more confusion by allowing a bare part of the tester to arc or short to the block.

[joshadurham]

Ok yea I’ll try out troubleshooting the ignition system. I’ll report what I find. Thanks for your help.

[joshadurham]

Update: I took apart my pressure fuel tank, and found it with a thick layer of old gas residue on the bottom of the tank. I drained the contaminated fuel and used some steel wool to break up and remove the junk. Luckily the tank turned out smooth and clean with no rust. I filled it up with fresh 100 LL Aviation fuel, mixed it 16:1. The motor started right up, and ran great. I even took it out on a small 10 foot flat bottom boat. Only let down is that it wouldn’t idle as slow and smooth as before. It ran smooth and strong in high Rpm’s. But just wouldn’t lean out like normal on the slow side. Won’t idle below "shift" it used to idle beautifully at "slow" on the throttle.

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