Bleeding a Small Ynamar Diesel fuel system

[Jeff_H]

Bleeding the Fuel System on a Small Yanmar Diesel.

I have always heard that replacing the filters and getting the engine bled after replacing the filters is a pain in the butt on the smaller Yanmar diesels. When I bought the boat in 2002, I had an independent mechanic check out the engine and in the process change the filters and change and check the fluids. Frankly, I have run so little fuel through the engine, that I have not felt the need to replace the fuel filters on my 3GM 30 since.

This weekend I figured it was time to change the fuel filters yet again and with that in mind I picked up the parts to do it myself. I firmly believe that as a general rule, as much as possible I should do as much of the maintenance on the boat as I have time to do as a way to keep current with the condition of the boat and to be able to make be self-reliant when it came time to make repairs whenever I may be.

Here I digress with a short story that is a bit off –topic……

Decades ago, when I lived in Savannah we went out to eat with some friends who had just moved to Savannah from California. They wanted to have dinner at an ‘authentic’ Savannah experience and so we went to dinner at a shrimp shack. This particular shrimp shack was a small ramshackle structure located on a dock within a shrimping cooperative compound. Out back were rows of shrimp boats tied side by side or laying long side to be unloaded of their catch. The air was filled with the din from winch on the sheer leg cranes being used to unload a boat alongside, the compressors that chilled the large walk-in coolers where the catch was stored waiting for shipping, pressure washer motors, the throaty shrimp boat diesel exhaust, and various sounds from a near by working boatyard.


Inside the shack were rows of wooden picnic tables lined up on the scrubbed through paint on a concrete floor that noticeably sloped to large drains that opened directly to the Thunderbolt River below. In the corner stood a pressure washer that was used nightly to wash down all of the surfaces and which gave the shack it’s scrubbed by worn appearance. The fingerprint laden, mimeographed menu listed few items, most of which were a reciting of grades, quantity by weight or bucket size of shrimp which clearly was the specialty of the house and only choice for a main course on the menu. The main course was delivered in various sized metal buckets and was dumped without ceremony on a piece of newsprint placed haphazardly in the middle of the table. Each diner was given a plate and a picking knife. The bucket was left on the table for the shells and entrails but most diners asked for an extra piece of newsprint and dumped the detritus there.

Our waiter was a short black man with a limp, who leaned to the side with his bad arm and one good eye, the other eye being hidden by fading black patch. Cigarette dangling out of the corner of his mouth he slammed a menu on the table and asked what we wanted in a strong coastal Georgian accent and with the low rasping voice that told of too many decades of cigarettes, cheap hard liquor and shouting into the wind. This was just the beginning of the time when waiters would introduce themselves by name when they came to the table. This trend must have started in California but was still a score of years from making its way to backwater Georgia. That did not stop our Californian friend from asking the waiter, “So, what do they call you?”


“Dey calls me Shorty,” the waiter growled back.


So our California friend says, “Ok Shorty, I’ll have a medium bucket of number…..”

But before she could finish her sentence, the waiter glared at her and snapped back. “I ain’t never sez I liked it.”


Which brings me back to the topic, while I am a strong advocate for maintaining my own boat as much as I can, “I ain’t never sez I liked it.”

I have bled a number of larger diesels and that was a piece of cake since they had electrical fuel pumps just for that purpose, and my small Buhk had been a piece of cake, but having heard all kinds of horror stories about bleeding small Yanmars approached this with some small amount of concern. I did a bit of homework and a bit of innovating and I thought that I would pass this along to others about to do the same. For convenience the tips are highlighted in bold.

First of all, my boat has as separate Racor filter. The great advice on this is to start with the Racor and do not touch the filters on the engine until I was finished with the Recor. To make this operation easier, I cut down a half gallon milk jug to catch spills just below the handle, which meant it was deep enough to hold the cartridge assembly upright and catch any spills.

The steps are pretty much as printed on the cartridge; remove the cartridge, clean everything thoroughly, lube the O-rings, screw on the bottom chamber if you have that kind of cartridge. And here is the next time saver, it saves a huge amount of work if you fill the cartridge and bottom chamber to the brim with diesel fuel before you reassemble it.

The next hint was very critical and helpful. Once the Racor is back together start the engine and run it for 10-15 minutes. This will save a lot of aggravation. There was a few missed beats but there was adequate fuel in the engine mounted filter to seemingly pull out whatever the air was trapped in the Racor.

Now to Yanmar’s built-in fuel filter. This is not all that hard but it’s where the biggest nuisance lies, so here are the key tips. Put the milk jug below the filter housing and make sure it fits and is out of the way. The steps are pretty much the same as the Racor; remove the outer housing, remove the cartridge, clean everything thoroughly, and insert the new filter on the stem. Before installing the outer casing fill casing with diesel to the brim and make sure the O-ring is perfectly in place.

Here is the part no one seems to tell you. You could be there pumping for half an hour if you only use the little pump to fill the casing and bleed the air out. The hot ticket is to remove the bleeder screw and fill the filter chamber to overflowing.

This is a bit of a pain in the butt since the hole is so small. In my case I used a tiny funnel roughly 1/8” in diameter and a cleaned out spice bottle full of fuel to slowly pour the fuel in. Other people tell me that they have used a veterinary hypodermic syringe or a small meat baster. Again fill to overflowing with diesel through the bleeder screw hole (it all gets caught in the milk jug below. Only then do you reinsert the bleeder screw and pump a few strokes to bleed the tiny amount of air left.

As a word of caution, you sometimes see people suggest trying to start the engine before bleeding the filter chamber. No matter what, Do not try to start the engine until you have bled the filter chamber. But once you have bled the filter chamber,at this point you might try to start the engine without doing any more bleeding. With any luck it will start and run fine.

One word of caution, a friend suggested cranking starter for a minute or more. Don’t. First of all, if you time it 15 seconds is an enormous amount of time to crank an engine, but you also risk flooding the exhaust system and then backing up into the valves. Bad idea….

In any event, if the engine does not run after only bleeding the filter chamber then bleeding the next short length of pipe is so easy that it is hardly worth it not to bleed this short piece by pumping the lever. I cheated and used my small funnel with some model airplane fuel line to fill the hole through the bleeder screw hole. It wasn’t worth the effort since the hand pump does this part so easily.

I will tell you that really old clothes and a good pair of rubber gloves is a nicety since you will be taking a bath in diesel. It’s helpful to keep a bottle to dump the excess diesel in as you clean out the old filters and the chambers. Otherwise its not too bad a job, that said, “I ain’t never sez I liked it.”

So that is about it. Good luck,
Jeff

[Jeff_H]

One more point here...If you go the route of trying to crank the engine for a long time to bleed the upper line, I suggest that you close the cooling water seacock to avoid flooding the engine.

Jeff

[thisisus]

One thing I did on my 2GM20 was to add a small electric inline pump between the racor and the engine. Did this when I had a fuel pump go out and was able to limp her home. After that neatened it up and left there with a switch. When changing filters I can turn it on and open the bleeder. Takes 5 seconds and easy as can be. I've ran it out of gas which is usually a pain to get them going again. Up and running in a couple minutes. My last boat had the 3GM in it and ran it out before (seems a common thread here) and it took forever to get that one going. Pump was around $20 at the parts house.
Thisisus
Islander 32
Mobile AL

[LittleWingCA]

Jeff_H:

Does your 3GM30 have a return fuel line to the tank or does the return fuel line go back to the Yanmar fuel filter housing?

On my Yanmar 2QM15 the return fuel line does not go to the tank but to a fitting on top of the Yanmar fuel filter housing. After draining my recor and yanmar filter housings, and replacing the filters, I just loosen the hose clamp on the return line that goes into the yanmar filter housing, and attach the hose to an electric suction pump. Once the pump is on, I place my finger over the return fitting, and the pump pulls the fuel from the tank, through the line, through the recor, through the line, fills the yanmar filter housing, and when fuel comes out the hose, turn off the pump, pinch the hose, and re-attach the hose to the return fitting I had my finger on. Tighten the hose clamp and you are done.

[thisisus]

that was on my last boat.....pretty sure it returned to the fuel tank on that one.
Thisisus
Mobile AL

[Northeaster]

As mentioned in simialr threads, the mechanical (hand) pump must be in the proper poistion, with respect to the camshaft. So, if you pump away for a miute or so, and don't see any air bubbles / fuel spirting out of the bleed hole, flip off the decompression levers, and hand turn the crank once. If still nothing, try again. When you get it right, you will feel slightly more resitance on the hand pump, and fuel / bubbles will start coming out.

[Selkirk]

When I'm ready to bleed the primary fuel filter and system I pressurize the fuel tank.

I do this by taking the vent tube loose and blowing a full lung-full of air into the tube. Had to blow two lung-fulls into the tank once when it was pretty empty. Then I stop it up with the proper size bolt.

Then I just open up the proper bleed screws and fittings and she bleeds herself.......