Zen and the art of diesel repair

Originally posted on July 9th 2007.

I have a 29 year old single banger diesel engine and when I bought the boat I was nervous about it. My boat would not easily take a retrofitted outboard and I could not afford a new inboard so I wanted to make sure I could get several years out of it and had it inspected by a mechanical surveyor. I have had no issues with the engine from the start. I did however not know/trust that any recent maintenance had been done so I quickly went out and purchased all the necessary hardware to “freshen” up the engine. I installed new engine anodes, belts, raw water impeller, changed the oil, and finally the fuel filters. As a DIYer I figured I could manage all of this myself and actually did all the tasks in one foul (and I do mean foul) swoop. Bleeding the fuel line though turned out to be a struggle for me. I had air in the fuel line and did not know how to bleed the fuel system. With a book I found on the boat “Be your own diesel mechanic” and a poorly translated YANMAR manual I figured it out and ran the electric fuel pump bleeding the system. Then unwittingly I set myself of a path of engine mayhem.I developed a small fuel leak that only seemed to happen when the engine was running. I could not find it for the longest time. I spent hours sponging out diesel smelling bilge water after each extended motoring. I finally found the source. I had stripped the primary fuel filter’s bleeder nut when I was originally trying to bleed the fuel system after a filter change. After consulting some online resources I found that I would have to either seal it or replace the filter head. I opted to reseal it and use the bleeder nut at the engine. Of course in sealing this nut I got air in the fuel system and had to bleed the air out of the system. I turned the ignition to the on position and diesel did not flow out. I thought I was doing something wrong so I started the engine up thinking that the system would then be under pressure and I could bleed it while it was running. Of course it sucked air in and died completely. I then was totally unsure and began cranking the various bleeder nuts off including the one I sealed in trying to bleed it closer to the fuel tank. It was with the help of a friend that I notice that when he turned the ignition on a little squirt of fuel shot through one of the bleeder nuts. With repeated turning on the ignition I could get a series of little squirts of fuel in rapid succession allowing me to bleed the engine. We then ran the engine for an hour with out incident. Thinking I was a fairly bright fellow I confidently set off the next weekend for Gibsons. No sooner did we get out around the break water did the engine sputter and die. We quickly readied the anchor and I went below to bleed the engine. About two minutes later the engine was back on and we were motoring along. After 3 more stalls in 20 minutes we turned around and headed home. The engine even stalled in the last few seconds when docking. After we had tied up we looked over the key culprit. The bleeder nut was stripped and not forming a tight seal. This likely was a result of my initial attempts at bleeding the engine coupled with it being 30 years old. We fashioned a temporary rubber gasket out of an old piece of rubber in the junk drawer and covered it in thread sealant. This time we made it to Lion’s Gate Bridge going against the flood before it stalled. We performed a quick turn while we had steerage, bled the engine, applied more goop and took off back on course. This problem plagued us all weekend. We had about 4 other stalls all after roughly an hour of motoring. In the end we got home safe but my confidence shaken. Having called the mechanic for advice I quickly learned that my fuel pump was definitely broken and needed replacing. I decided to replace the filter housing at the same time since I would be unhooking the fuel system anyway. I now have the parts on order and will make a photo album with the repair process.