Join Date: Oct 2009
Location: Swarthmore, PA
Thanked 143 Times in 132 Posts
Rep Power: 11
Re: 2017 Sailing Season on the Chesapeake
Gorgeous day today. Seemed like a nice breeze in the morning, but died around 10 am, so we didn't bother to go out.
My fuel filter replacement went well - I think. I waited until this morning so I'd have more natural light. The secondary filter came right off without a tool - possible cause for concern as a source of air contamination.
I'm very glad that I did not proceed to Corsica and attempt a fix there. My filter wrench was big enough for the Universal secondary filter, but not big enough for the spin-on Racor primary filter. So I would not have had all the needed tools. And it was much nicer working on a cold engine, with A/C running in the slip.
My fuel system has a recirculating arrangement where fuel goes though the banjo washers and back to the tank, continuously polishing the fuel. Some Catalina owners go so far as to suggest installing the secondary filter dry and letting the recirc system pump filtered fuel into the secondary filter to displace the air. I opted not to do this, figuring a few ounces of fresh fuel would never have enough particles to plug the secondary filter. I did not want to risk having a huge slug of air going through my system, even though the recirc system should, in theory, remove the air.
The Racor system is the less user friendly spin-on type (instead of the nicer type with drop-in filter), apparently selected due to limited vertical space under the aft berth. As a result, you can't really inspect the filter - you just take it off and can get a little bit of a look inside after you dump the fuel out. Once I had borrowed the needed wrench from a marina neighbor, I got the thing off, dumped the fuel, cleaned the bowl, refilled with fresh fuel, and got it back on. Primary filter definitely looked worse than the secondary filter, but that might just be an optical illusion because the sec filter captures particles too small to see with the naked eye.
I primed the system by running the lift pump for about 5 minutes to recirculate all the air out (or so I thought). I chose to do this on 50% duty cycle, because lift pump is wired with the glow plugs and I didn't want to burn them out.
Motor started up fine, but after about 3 minutes at 1200 RPM it starting shaking and I had to kill it. I started worrying about a plugged injector. But after about a 30 minute wait and more priming, it started again, shook for a split second, and then ran fine in the slip for about an hour. The true test will come next time I take the boat out.
I suspect that what may have happened was as one of the filters developed resistance to flow, a negative pressure may have built up sucking air through the loose secondary filter. That could have brought in enough air into the injector pump to mess things up between the recirc loop and the injectors. Obviously I could have bled the high pressure lines up to the injectors, but I'm glad I didn't have to because turning the wrong nut by the injectors can screw up injector adjustments, requiring sending back to the factory for re-adjustment. (Your ordinary shop down the street can't do it.)
I am still seeing some little "effervescent" bubbles in the Racor bowl when the engine runs. I think this is just some air that was trapped at the top of the primary filter getting broken up with the motion. They seem to be disappearing gradually. I'll continue to monitor just in case it's an air leak.
Rick S., Swarthmore, PA
USCG Certified Captain, OUPV and 50 Ton Master
ASA Certified 101/103/104/105/106
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2001 Catalina 34MkII Tall Rig Wing Keel Breakin' Away, Universal Diesel M35B, Mantus 35 lb. anchor, sailing out of Rock Hall Landing Marina