Bleeding a Yanmar 3GM30F - SailNet Community
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post #1 of 7 Old 07-26-2008 Thread Starter
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Unhappy Bleeding a Yanmar 3GM30F

Hello All,

We have a Yanmar 3GM30F in our 1990 Caliber 33. After a pleasant early evening sail. We fired up the engine to motor into the inlet of our harbor and had problems with engine stalling at RPM's over 2000 and under 1000. Once I found the range she would stay running I was able to limp her into the harbor and to our mooring.

The gauge next to the Racor filter was clearly in the red. I usually have the yard spring commission the engine and the filter usually lasts through our 6 month Long Island sailing season. I've actually never had to change one myself.

I read through various diesel engine books that I have aboard including notes from a Mack Boring seminar I attended a few years back.

I removed the Racor filter and looked inside it didn't look dirty, but like I said I never changed one before. I filled the new filter and bowl with fuel right to the top. Smeared some fuel on the O-rings and hand tightened her up as the books recommended.

Then I proceeded to remove the bleed screw (phillips head) from the secondary filter. I can't believe Yanmar chose to stick the thing up under the heat exchanger . I was able to get a wrench on it but had no room to swing the wrench. I had to remove the other screw on top of the filter to remove the bleed screw.

I operated the lift pump and was not getting any fuel out of the top of the secondary filter. I put back the outer screw and tried again, nothing. Actually I wound up with a small amount of fuel on my fingers which I was using to operate the lift pump. For those of you not familiar with a Caliber 33, starboard side excess to the engine is visually limited. I use a mechanics mirror just to put the oil dipstick back into the engine. I had to use a mirror to see the screws on the top of the secondary filter.

I replaced the bleed screw on the secondary filter and started the engine. She ran for about 2 minutes at about 1000 RPM's before she stalled. I was not able to get her to start after that. Finally I said uncle and called the mechanic where we moor our boat.

The mechanic was not able to get fuel into the secondary filter. He found that the hose running from the primary filter to the fuel pump was cracked, probably original hose. He replaced that, but still no fuel. He ordered a new pump which he is waiting for.

I didn't really delve into it any deeper because I figured I was doing something wrong. This is from someone that when my SUV doesn't run correctly I take it to my mechanic.

Depending which book you read. Some say that in most cases you only need to bleed up to the secondary filter while other books say you should bleed the whole system up to the injectors .

I just haven't been able to figureout the iron Jenny . Give me circuits, electronics, computers, and I'll make them work . Gears, belts, and fuel lines have got my number .

Thanks for your replies.


S/V Sailor Dance
1990 Caliber 33
Long Island Sound
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post #2 of 7 Old 07-27-2008
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We had the same engine and same problem. The deal with the Yanmar's is that when the fuel pump goes, your're dead in the water. We had some little outboard squeeze bulbs in the fuel line for priming and I finally bought an electric fuel pump installed in-line after the racor filter to supplement the yanmar pump (which is a piece of crap). After installing the new fuel pump, no problems.

Good luck! Nothing worse than a diesel that won't run.

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post #3 of 7 Old 07-27-2008
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From Yanmar.... BLEEDING AIR I also use a priming bulb installed in line before the filter to assist in bleeding filters.
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post #4 of 7 Old 07-27-2008
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The fuel system has two sections - a low pressure section and a high pressure section. It's important to understand where one ends and the other starts. I'll try to describe that here. Once you understand them you can then learn how to bleed them.

It's helpful to know where the lift pump is and where the high pressure injection pump is. From the bleed point entering the high pressure pump back towards the secondary fuel filter, lift pump, primary fuel filter, and tank is all part of the low pressure fuel system. Removing air from this system is always step 1. If you work on the low pressure system, for example changing fuel filters or the lift pump you do not normally need to bleed the high pressure system. The high pressure system includes the high pressure fuel pump, the high pressure fuel lines, and the injectors. To find the high pressure pump, follow the lines coming off the injectors to where they meet in a row on top the the high pressure pump. Another clew is the final bleed point from the low pressure side, it too attaches to the high pressure pump.

If you work on the high pressure system, such as replace a high pressure fuel line, or as in your case, run the engine without the low pressure system being air free, you introduce air into the high pressure system.

(Note: You can also introduce air into the high pressure system by completely filling the secondary fuel filter with fuel before installing it on the motor. Leave it empty or no more than half full before installation. People do this to minimize the hand pumping, but it traps a slug of air in the low pressure system, which will end up in the high pressure system)

Once you get air in the high pressure system you need to bleed the low pressure system first, then bleed the high pressure system.

It sounds like you are familiar with bleeding the low pressure side. The high pressure side is pretty easy... once the low side is air free, follow the lines fro m the high pressure pump to the injectors. This step shows you which is the injector inlet and which is the outlet (or fuel return). Open the connection at each injector 1 full turn. All injectors are bleed at the same time. (The engine cannot start with these lines open). Do not remove the line from the injector or bend it. Now just turn the engine over with the starter until fuel comes out of each loosened nut. Only a very small amount of fuel is pumped each revolution. (Do not pull out the engine stop during the process or it wont work.) Then tighten each fuel connection at the injectors. The need to be tightened more firmly than the low pressure side since they run about 2,500 psi. Now try to start the engine. If it starts and runs for 10 minutes you are done. If it stalls, re-bleed the low side, then the high side again.
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post #5 of 7 Old 07-27-2008
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You did not say if you checked the engine fuel filter. If you are following Yanmar's recommendation to run a 10 or 30 micron (depending on who you ask) in the Racor and a 2 micron on the engine, you could easily have a clean looking Racor and a fouled engine filter.

I have had the same engine in my last two boats. My experience with the symptoms you mentioned is that it is usually caused by a fouled fuel filter or less likely air in the line due to a loose or split fuel line before the pump. I personally use a 2 micron element in the Racor and rarely ever have to mess with the engine filter which is harder to change. There was a discussion about this recently on another thread. Try searching for "racor".

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post #6 of 7 Old 07-12-2015
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Re: Bleeding a Yanmar 3GM30F

Can you provide more info about your installation of an electric pump, please?
Thank you,
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post #7 of 7 Old 07-12-2015
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Re: Bleeding a Yanmar 3GM30F

On the 3GM30F, there is a second bleeder screw for the injector pump. It is not obvious, being under the exchanger hose on the top/left side. I have a 3GM30F and took a while to find that bleeder. If you don't first bleed the filter and then the injector bleeder, the engine will never start. Once you get fuel to the injector, the engine will fire right up. Don't mess with your injectors/banjo fittings YET. Once you crack those banjos, you may wind up having to replace the washers. Your original problem was almost certainly the cracked hose. You just need to bleed the second bleeder screw. +1 on having an outboard squeegee.

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Last edited by smurphny; 07-12-2015 at 09:40 AM.
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