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The culprit of our air leak, we think

Cruising is fixing your boat in exotic (or non-exotic, in our case) ports. I knew this going in, but the engine issues have given me a harder time than expected. I am not the best mechanic but I’ve learned so much recently.

The entire fuel line from the tank to the fuel injectors have been taken apart more than once trying to figure out the problem (some parts probably half a dozen times). I’ve gotten very good at bleeding the air from the fuel line without a bleed point at the highest point and without the assistance of an auxiliary electric fuel pump. But I often reak of diesel odor for days afterwards.

Yes, I can buy and install an electric fuel pump (which I probably will in the future), but I’ve learned that the cruising lifestyle is mostly about making do with what you have. For example, I’ve used a hand suction pump to help bleed the engine and a hand bicycle pump to pressure test the system. And when the bleed screw on the primary filter housing got stripped, I had a local machine shop weld the hole closed. The thought of replacing every piece of the fuel system was considered more than once. But I never would have found the problem, nor would I have learned as much.

Boat mechanic guru Nigel Calder in his Marine Diesel Engines book describes a persistent air leak into the fuel system as one of the hardest problems to troubleshoot.

So, what was the source of our air leak? There were probably two culprits, both in the vicinity of the primary fuel filter (which I now have a spare filter assembly for): a stripped bleed screw and a corroded metal gasket (see photo above).

How did I find the culprits? At first, my approach was to go after the most likely offenders, namely the fuel filters. But problems persisted after changing both filters. Then I put rescue tape on as many of the joints on the fuel system as possible. Still problems. I then had a machine shop weld shut the bleed screw on the primary filter assembly (I wanted them to re-tap a hole for a bleed screw). Still problems. Ugh! I felt like throwing in the towel & calling a mechanic for help. But with the encouragement of a circumnavigator in Newport, RI, I persisted (thanks Sten).

I hooked up a bicycle pump to as much of the fuel system as possible to pressurize the fuel lines and to spot leaks with soapy water. Found no leaks. The only part that I was not able to pressure test was the primary fuel filter assembly. The bleed screw was already plugged up, so I went through all the pieces on the filter assembly and found one metal gasket that was corroded and cracked. Armed with extras from a trip to the Volvo dealer (because I lost one to the bilge the previous week), I replaced the metal gasket and the engine has been working since.

Some things I’ve learned from working with our diesel engine:

  • Have lots of gaskets and washers as spares. They are cheap. And supposedly the metal gaskets or crush washers are only supposed to be used once and then replaced.
  • Over tightening is bad. Broken banjo bolt. Stripped bleed screw. Now when I use adjustable wrenches on the engine, I use the one with the smallest handle so I can’t over tighten too much. Funny side note – I had just read ZTC’s post on too much torque the day I broke the banjo bolt.
  • Prolonged exposure to diesel fumes in cramped quarters often with my head below the rest of my body in a rolly anchorage impairs my judgement.
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4 Replies to “Engine rant (not to be confused with the coupling saga)

  1. Tig, I wish I could give you a great BIG HUG!!!! Tenacity at its finest. You are AWESOME! Congratulations and love to you and the family. Miss you all. Lauren 🙂

  2. Tig,
    Wow – we just followed in your footsteps this week! What a frustrating, smelly, sweaty (at least in the Mexico summer) job this is. We FINALLY traced our leak back to the junction of the injector pump and high pressure line…after about 6 days of fiddling, getting covered in diesel and pulling our hair out…..then ALMOST calling in the mechanic. Thanks for the rant, I’m sure we’ll be posting ours soon also! 🙂
    Katie and Mark

    1. Katie & Mark,
      Glad you solved your engine problem too. There are much more pleasant things to do. I see you did not put”have kids” on your progression timetable. That one slows everything down. So glad you guys are deciding on this lifestyle as well. Fair winds & hope we meet up someday.

  3. Tig,
    One of the best little tools that I got was this giant syringe from Amazon. IT is originally used to mix oil and gas, but you can do many other things with it: It has a tapeded end, so you can adapy it to a 1/4 inc hose
    I did :
    Remove the water form contaminated fuel
    Blew free a contaminated clogged fuel hose
    Able to verify lack of leak by applying vacuum
    Check fuel consumption by running engine directly from syringe
    Use it to fill suck out and fill exact measured oil into transmissiom
    Bleed hydraulic autopilot
    Fill fuel into primary filter and force it downstream to easily bleed the air.
    It is only $11, and I have 2 on board always. If you are interested, search Amazon. If you can’t find it I will send you a link.
    Ahmet

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