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Old 06-03-2018, 08:22 PM
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Unhappy A Puzzle: Engine seems to be running rich or burning oil but has good compression

I have a new to me A4 out of a freshwater sailboat that has been converted to fresh water cooling. The old engine was having challenges with oil pressure and even after adjusting the oil pressure to 60 PSI at idle it would drop to 10 at when hot at idle so I jumped on the newer A4.

It was in visually just about perfect shape, no rust and looked to have little use. The folks just used the engine to get clear of the dock and to return to the slip. The compression was 110 psi on cylinder 1-3 and 90 psi on #4 and it didn't improve with a squirt of oil. The lead to me that one of the valve seats may be touchy, and I'm not sure overall accuracy of the compression tester since we used the seller's, but nice older Craftman, before Sears sold out.

I installed tne 'new' A4 and I seem to have a problem with smokey exhaust. First thing, i took the carb apart and cleaned it and that helped with starting but I had problems with a bit engine RPM varying and idle or under consistent throttle setting. Not horrible, but annoying. Since I don't know a ton about this engine, I spurged on a new carb from Ken at MMI and installed it this weekend plus the engine came with the Indigo PCV kit. I also replaced the plugs with with the RJ12C (0.035" gap) and notice when I pulled the old spark plugs the were all uniformly sooty, with the #4 cylinder spark plugs was 'moist' a touch of oil on it.

So I squirted a bit of MMO into each cylinder as it replaced the plugs and let it sit for an hour or so before starting. Got the traditional whiteish smoke and then settled down to looking like it was running a bit rich but better than with the old carb and plugs. I adjusted the carb in about a half turn for 1 turn out from seat. That seems to be where it idled the best.

Next, I dug into the distributor removed the Pertronix base plate and checked the advance mechanism. Nothing stuck and everything moves, but the advanced springs seem pretty light, I could easily turn the rotor by hand and max out the advance ... but I'm not an expert.

I then timed the engine at 1800 RPM tied at the dock and got the highest RPM and backed off a touch. It's maybe a a bit better on the exhaust smoke but more than it should. At this point the engine starts perfect with the new carb, no idle creep (one thing fixed! ) and has been run for about 30 mins since the carb install.

So being curious, I pull the spark plugs and they all looked just like the old plugs! All were sooty and a bit moist on #4. The boat is 2+ hour from home so I put about an 1oz of MMO in each cylinder, reinstalled the plugs, pulled the coil wire and 'bumped the starter' to help toss the MMO around head/valves... reinstalled the coil wire and drove home.

I'm hoping the MMO will help clean/loosen something... but I'm grasping at straws. I was not expecting sooty spark plugs after 30 mins of operation.

Any other wisdom, thoughts and/or ideas?

Thanks,
Ron
Portland, OR
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