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Stumbling Yanmar

Tom Plummer

Member III
The saga of the stumbling Yanmar 3GM30F It all started about 5 years ago. For the first 10 years we owned Jessie I changed the Racor fuel filters regularly and life was good. I was unaware that there was a filter on the engine and had never fussed with it you see. Then came the load of very bad fuel from a fuel dock and life changed. While pleasantly motoring along with landlubber guests aboard the trusty Yanmar sputter to a stop. Now as luck would have it the Lord smiled down on me that day and at that precise moment a 10knt breeze sprang up and we happily sailed into Coronet Bay. Where to our good fortune was a fellow sailor who just happened to have the correct filter on board in quality so soon we were on our way again.

The rest of our cruise was blessed with wind and so we never ran the Yanmar for more that about an hour at a time so life was filled with bliss.

On our next trip the wind was dead calm so we cranked up the once trusty Yanmar only to have it misbehave. After about 1.5 hrs of running it would drop from 2800 rpm back to 1800 rpm then fluctuate between the two for about 15 seconds. Then it would operate normally at 2800 rpm for about 10 min and repeat the cycle. Occasionally it would just quit and then after about an hour it would just mysteriously restart when we spun it over. I replaced all of the filters to no avail. I had the tank polished to no gain. I check all of the fuel fittings, replaced the exhaust water injection elbow verified there was no blockage in the exhaust system, verified good cooling flow bout raw and fresh, and even ran with the fuel cap off but, nothing worked.

So for 5 long years this has been going on. Admiral Marilyn became less and less enthused about my beloved Jessie and there was even talk of replacing her with a trawler. So as I motored down to the PNW Rendez Vous and it happened again as it always does I figured that this would be my last trip in her.

But, once again the Lord was smiling on me and their on the dock was none other than Glen the Great of California E31 fame. While am relating my sad tale of woe before I can identify the manufacture of the miserable hunk of iron that was giving me such pain he states you have a Yanmar don’t you. He then asks if I had seen his post about the primary filter bowl installation process for the Yanmar. I had not so he proceeded to enlighten me on the proper means of reinstalling the filter canister on a Yanmar.

His instructions were quite simple loosen the locking collar shake the canister slightly to wet the o-ring with fuel rotate the canister to insure that it is not going back in the exact same position. Then while gently Appling a polishing motion to the center of the bottom of the canister tighten the locking collar with you other hand.

I am happy to report that the engine ran like a top all the way from Port Townsend to Anacortes never missing a beat.
 

Tom Plummer

Member III
Alas then next time I used the boat the problem was baaaack. After a discussion with the Yanmar Rep at the Seattle Boat show I did the following.

Replaced the lift pump, they are incredibly weak having a rated lift capacity of only 3.5” and installed a electric flow through booster pump between the tank and the primary fuel filter.

5 years ago at the start of this mess I was the victim of some bad fuel I had the tank polished and all of the fuel lines cleaned at the dispenser of the bad fuels expense. But, it turns out that polishing the tank and cleaning the fuel lines will not clean the fuel pickup tube especially if there is a check valve installed at the tank. The combination of the weak lift pump and the low fuel flow rate of the Yanmar 3GM30F about 0.5GPH meant that the gunk in the line was never sucked out into the filter. It just stayed in the fuel pickup tube slowly traveling up the tube until it hit the check valve where it would stop and eventually starve the engine for fuel. The engine would slow to a bear idle the gunk would fall back down the tube allowing fuel to flow through the check valve again. The engine would resume normal operation and the cycle of woe would start over again.
It was while installing the booster pump that I discovered all of this.

Finally the cause of all of my engine woes is known. The pickup tube in the fuel tank was full of gunk, see attached photo.

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To clean the pickup tube which can not be removed from the tank I made a recirculation loop in the fuel system. After three new filters in the Racor, the first two plugged up tight enough that the boost pump shut down, the system was free flowing enough to just use the Yanmar lift pump. The loop will come in handy in the future to self polish the tank. See diagam

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To allow myself to ability to run the booster pump without the warning buzzer sounding I wired the pump directly to the battery buss just after the battery disconnect switch. I installed a double pole double throw switch to control the pump. In the fill/recirc position the pump will run as long as it has power. This position is used to refill the filter after changing the filter and for polishing the tank. The run position will run as long as there is oil pressure and power this precludes the possibility of pumping a tank full of fuel into the bilge if you break a fuel line. The center position is OFF. Electrical Drawing below.

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I hope that some of you can find this of some use.
 

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Tom Plummer

Member III
:egrin: Oh by the way to test the engine and give that Admiral :wife: the confidance she need to be willing to go sailing again I powered to and from the PNW gathering of the Vikings. It is 31.7 miles each way which worked out to 6 hrs each way. The Admiral has declared to porblem fixed :Kissy: and is now excitedly planing our next trip.:)
 

CaptnNero

Accelerant
sump access tube, bleed screw

Tom, your fuel polishing system sounds very worthwhile. I'm going to look into that myself. Because of unknown fuel quality issues, you might also want to install a fuel sump access tube immediately above the sump in your fuel tank as depicted in Nigel Calder's superb boat mechanical & electrical book.

Such a tube allows you to sample and pump dirty fuel from the sump whenever you want. Instead of hovering about an inch over the bottom of the tank as the fuel pickup does, the sump access tube goes much closer to the tank bottom. Then with a hand pump you can quickly siphon the dirt and water that gravitates to the lowest spot (sump) of the tank until it comes out clear before turning the rest of the cleaning over to the polisher.

My own experiences this spring with fuel quality problems led me to the idea of a sump access tube, and then I saw it in Calder's book. Now I am planning to put one in during our winter layup. Fuel tank sump access is routine on small airplanes; why not on boats ?

Your engine symptoms also were somewhat reminiscent of a cracked nylon Racor filter bleed screw that presented itself immediately after my recent fuel contamination. It would run fine for one to several hours, then within a minute the power would drop off until it totally quit as the lift pump became airlocked. My point is that you might want to make sure your Racor has the replacement brass bleed screw instead of the crummy nylon one to avoid any future strife with the admiral.

Good luck.
 
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footrope

Contributing Partner
Blogs Author
Anxiously waiting for your next report

Tom,

Can't wait to hear about your next couple successful trips - with no engine problems. Your report about the clogged pickup tube is most illuminating.

As the owner of an early E38 I have wondered about fuel contamination and the issues that go with it. We have future "inside passage to Alaska" plans and I have to think a good supply of extra filters is a must. Would you do anything different about taking on fuel as a result of your experience? I wonder about pre-filtering options that wouldn't be too time consuming and over-cautious looking to use everywhere? Our marina is in a river mouth and behind a bridge. An engine failure anywhere in the 15 minute cruise into or out of the area would be tough. We keep the anchor ready.

As an aside to this, when my diesel heater was installed this past winter, the installer reported that the plastic access cover ring on the tank had cracked, due to age, and asked permission to replace it with a gasketed aluminum cover. I agreed, and before they were done I went down on one of my many progress checks and was able to see inside the tank. Nice and clean. There was a little line of stuff that settled into the inside of a bend - the low point - but I was glad to see that the PO had probably taken good care of the fuel system.

One mysterious piece of gear he left me was a 2 foot long piece of 1/8" copper tubing with about 4 feet of clear tubing attached to one end. Could this be for manually sucking small amounts of gunk from the tanK? He stored it under the aft quarter berth cushion, right above the plywood tank access cover. I have puzzled over this and wonder if anyone else has a guess.

Have a great next trip - sorry I missed the fun this year. Today I change the oil, oil filter, and fuel filters in preparation for next weekend's voyage.
 
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