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Last week as I was motoring out to a club race, my engine died suddenly, and would not restart. (Aside - a generous competitor graciously towed us out to the starting line and another towed us back to the dock after the race. Thanks to my friends at LSYC.) What transpired later was a lesson in contortionism and humility. I want to share what I learned.
The problem was pretty obviously a fuel system problem. All the nasty possibilities raced through my mind - bad fuel, water in the fuel, algae, clogged pickup, clogged filters, clogged injector, failed pumps, no fuel <img src="emoticons/icon_exclaim.gif">, pinhole air leaks or cracks in the fuel hoses, etc. It's amazing how many things can go wrong with a simple system. Unfortunately, as it turned out, I started debugging at the wrong end of the system. I started by changing the primary engine-mounted fuel filter. The element was dirty but not clogged. (By the way one "expert" told me these filters should be changed annually, even if you have a secondary (Racor) water-separating filter - which I don't, yet.) Then I tried seeing if there was fuel getting to the bleed screw at the input to the high-pressure pump. Nada. I traced my way back up the fuel system one bleed screw at a time and never saw any fuel. By the way, one important lesson was to learn how many times you need the flick the annoying little lever on the low-pressure pump before it is reasonable to expect to see fuel. I had no idea when I started and must have flicked the damn thing a couple of thousand times 'till my fingers all hurt! The answer is, to fill the whole line including an empty primary fuel filter requires 180 strokes! Eventually I got directly to the bleed screw on the output of the low-pressure pump. Ah! A gush of fuel -- very misleading. After much more futile debugging I went back to that bleed screw and realized that what I had seen was just s little fuel sitting in the line. I actually had no output from the low-pressure pump. So I was sitting there under the cockpit with bruised ribs wondering what to do with my legs so I could get my head and arms in where they needed to be, dreading the next step of replacing the fuel line or taking the fuel tank apart. Not having a spare fuel line at hand, I decided to tackle the fuel tank. What I found was suspicious. (No, cynics, it wasn't an empty tank!) The fuel is sucked out of the tank through a threaded in fitting on the top of the tank, with a hose barb inside the tank. Attached to the barb is a plastic tube that goes down to the bottom of the tank. This is an interesting design, since it ensures that the engine will pick up all the water and crud off the bottom of the tank before getting any clean fuel. (Diesel fuel floats on water but crud sinks in it.) So far I had found no obstructions or clogs anywhere in the fuel system. The critical observation was that the plastic tube didn't seem like it fit on the barb too tightly. So, off to the local marine parts store (Bristol Marine in Port Credit) for the second or third time, to buy a new (fire rated) fuel hose and plastic tube. Apparently, the tank pickup assembly is quite standard (a big surprise in the marine industry) and is only sold as a unit. The plastic tube is joined onto that metal barb incredibly solidly. This gave me some confidence that I was finally on the right track. My theory was that the old pickup tube was allowing tiny amounts of air from inside the tank to enter the fuel line, and the engine just wouldn't run on diesel vapour alone! To make this a little clearer, please take a look at these two pictures:
<A href="http://members.rogers.com/rsengland/images/FuelTank.JPG">http://members.rogers.com/rsengland/images/FuelTank.JPG</A>
The first one shows the top of the fuel tank with the fuel feed line disconnected and the pickup assembly removed. The second fitting visible is the fuel return line.
<A href="http://members.rogers.com/rsengland/images/FuelPickup.JPG">http://members.rogers.com/rsengland/images/FuelPickup.JPG</A>
The second picture shows the fuel pickup assembly on the left side and the shutoff valve that screws into it on the right side. Notice how poorly the plastic tube fits on the barb.
Next day (by this time I could barely stand up straight), I installed the new pickup assembly in the tank. After 180 more strokes on the low pressure pump lever, I had fuel at all the bleed points. Then, after cranking the engine for a while, the high-pressure side of the system managed to bleed itself (this is a nice thing to know about Yanmar engines, since bleeding the lines to the injectors can be a pain and even a dangerous job), and the engine started! Problem solved.
What do I wish I had done differently? First, I should have started with the bleed screw directly on the output of the low-pressure pump. Second, I shouldn't have been fooled by a small amount of fuel coming out there that was just left in the line. Third, I shouldn't have wasted time and energy pumping the low pressure fuel pump priming lever so many times -- after a couple of hundred strokes, if you aren't seeing fuel you aren't going to! Lastly, I shouldn't have been so reluctant to open up the fuel tank. It didn't turn out to be as difficult as I feared.
Congratulations to anyone who has read this far.
Bob, S/V Heatwave
Bob, I know where you are coming from. After I installed a 2GM20 It would run fine for about 8 hours and then cough, sputter, and quit. Bleed the system and it would run for another 8 hours. Problem, air getting into fuel. As this was a new installation the solution was to redo all the hose connections. It is amazing how little air it takes to mess up the system.
Also, When I built my fuel tank, I used a piece of Stainless hydraulic tubing for the fuel pick-up and have it set 1/2" from the bottom of the tank. Seems to work fine.
Ralph Ainslie
"Hyperion" 27 Mk1
Hi Ralph. I would like to hear about your 2GM20 you installed on your boat. How difficult was it, what cost and how is the sound level when under power. I have a YSM12 Yanmar now and love the power it provides, but on a day with no wind it's a killer to listen to the sound of a single cylinder diesel engine.
Bob Wilson
Bob, When I fire up the 2GM20 it sounds like it is going to throw a rod. You would almost think it was not getting any oil. When you bring up the RPM the hammering goes away. I have checked with a few other owners who have this deisel and they tell me it is just the nature of the beast. Once I had my fuel problem solved, the engine works like a dream.
I only used a waterlift muffler and I don't know if this is the reason, but the 2GM20 is louder than the Atomic four. I guess I am just getting used to it. I'd much rather put up with a little more noise than to not hear anything as was the case with the atomic four.
Ralph Ainslie
"Hyperion"
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