Yanmar fuel problem: air leak?

[jaysweet]

Two days ago, I ran the engine (Yanmar 2GM20F) on dry land to test it before today's launch date. I mean: I ran the heck out of it. Usually, I just do one bucket of water-worth, but this time, I had a garden hose going into the bucket, so I did maybe 3 buckets worth (say 3-4 minutes). It started a tiny bit hard (as usual after sitting), but started right up and ran flawlessly, as it has for 18 years.

This morning, I was picked up by the Travelift, and put in the water. Checked below, adjusted the stuffing box, and tried to start it. It would always catch for a few seconds and then die. After many attempts, they handed me around to a nearby slip (not my own). I hung my head in shame...

My first thought was: what changed since it ran 2 days ago? The boat was vibrated and moved, so maybe sediment stirred up in the tank and clogged the fuel filter. I went and bought a new filter. Changed it out: the fuel drained from the bowl looked almost perfect. Just a few specks of black, and no water. Tried to start it again: same behavior. Tried bleeding at the secondary (the one on the engine, I think?). I believe I did see a few seconds worth of foam, and then steady fuel. Wouldn't start. Did this 3-4 times with the same result. Tried bleeding at the bolt on the engine after the secondary: I think fuel was coming out fine. No start.

Went back to the primary, which is a Racor 120RMAM with a R12T screwed into it. There's a little puddle under it, which maybe I didn't clean up when I changed the filter? Wait: there's fuel on top of the filter around the "head bolt" which screws into the filter:

I wiped this down (I think I did last time, but...) and it keeps seeping out. Did it a few times: still seeping. You can see the red in the photo. So at this point, I'm thinking: if fuel is getting out, air is getting in. Here's the head bolt:

So it's got a couple of o-rings and a metal washer, none of which are spec'd by Racor separately. I ordered a kit that I think (?) will contain these, but not from Racor.

I really hate these things where more than one thing may be going wrong at the same time. If this air leak is the problem, then why did it magically occur between my running on land and when I launched today? And now that I'm no longer at the boat, maybe I didn't screw this bolt down far enough? (Actually, I did torque it down pretty good.) Putting on the filter/bowl combo is come combination of spinning it onto the bolt (which protrudes through the top piece), and then finally tightening down the bolt to snug the filter up to the top piece. Maybe I should have just done this all over again from scratch, but at that time I was getting tired.

Anyway: I've read for years and years about gunk in the tank clogging filters, and about air leaks and bleeding. But to be honest: my 2GM20F has just run flawlessly for 18 years. I'm not even sure I've ever bled the fuel lines before! I just fill the filter and bowl up to the top when I change the primary, and screw it on. It always starts right up. Never had a problem. So that leaves me without much in the way of coping skills now. I tried to bleed the dang thing many times today before discovering the leak on the top of the primary, so I'm hoping that's the problem. Any and all advice is welcome! Thanks.

 

[jaysweet]

Reading and thinking: Occam's razor is now making me wonder if I pulled up the mechanical stop lever 2 days ago and forgot to push it back down. That wouldn't explain the fuel leak at the filter, but as I said: sometimes more than one thing is happening at once. Never rule out stupidity, that's my motto...

 

[Ralph Johnstone]

Your filter body doesn't match the Racor 120RMAM series.

But that aside, any time you find an external fuel leak, it's a good chance for air to enter and the centre bolt looks to be a good source of air with the flattened O rings.

Can't really see what purpose the bolt serves other than being a R12T filter by-pass in a tight situation. I imagine the head of the bolt has an arrow on it ?

Any reason why you chose non Racor replacemnt parts ?

 

[Ralph Johnstone]

wonder if I pulled up the mechanical stop lever 2 days ago and forgot to push it back down.

Not likely because that's MY specialty after fuelling up .

HOWEVER, what I've seen on my 2GM20F is that it will not even cough if the stop is pulled and you try to start.

I pulled up the mechanical stop lever 2 days ago and forgot to push it back down. That wouldn't explain the fuel leak at the filter,

Can you elaborate why you think that caused a positive pressure on the bolt in the 120RMAM as opposed to the same situation when the engine is shut down ? Your fuel level sounds like it's well above the level of the filter.

 

[jaysweet]

Your filter body doesn't match the Racor 120RMAM series.

View attachment 205313

But that aside, any time you find an external fuel leak, it's a good chance for air to enter and the centre bolt looks to be a good source of air with the flattened O rings.

View attachment 205314

Can't really see what purpose the bolt serves other than being a R12T filter by-pass in a tight situation. I imagine the head of the bolt has an arrow on it ?

Any reason why you chose non Racor replacemnt parts ?

Ralph, I think (by what I'm seeing online) that the 120RMAM was replaced by the 120RMAM2, which no longer has the bolt. That's probably what they mean by "series". The part we have seems to agree well with the one at this link:

https://www.racorstore.com/PDF/12945_Rev_B_(120RMAM).pdf

I suspect the main point of the bolt is that it makes it easier to get the filter off (vs. just spinning it off the top part). Clearly, they've done away with it in later models, maybe b/c it's another point of failure. Although it's worked perfectly for 18 years, so no complaint from me. No arrow on the bolt. I think the holes don't have to line up with anything.

It actually looks like the kit I ordered

[RK-10063]Parker Racor KIT-REPLACEMENT GASKETS 120

[RK-10063]Parker Racor KIT-REPLACEMENT GASKETS 120

www.dieselfiltersonline.com

is probably a Racor product.

https://www.parker.com/parkerimages/Racor/10065%20Rev%20-%20(110%20&%20120%20Rebuild%20Kit).pdf

 

[jaysweet]

Not likely because that's MY specialty after fuelling up .

HOWEVER, what I've seen on my 2GM20F is that it will not even cough if the stop is pulled and you try to start.



Can you elaborate why you think that caused a positive pressure on the bolt in the 120RMAM as opposed to the same situation when the engine is shut down ? Your fuel level sounds like it's well above the level of the filter.

You're probably right that possibly failing to push the stop lever back down (which I'll obviously check next time I'm out anyway) doesn't seem particularly consistent with the 2 problems I observed: catching and dying, and the fuel leak.

Actually, my fuel tank sits quite a bit higher than the filter, at least when it's full. For example, if I forget to flip the fuel cutoff at the tank and open the drain under the fuel filter, the fuel tank will gladly fill whatever container I'm trying to use to catch the 1-2 cups of fuel from the filter. Yes: I regularly forget about the cutoff, and have to scramble to put the drain back in so I can flip it...

I suppose it's possible the cable clamp on the stop lever slipped loose, so it's cutting the fuel flow off partially. Another thing I'll check. Some years ago, I think a solenoid in the fire suppression system stopped the electrical fuel stop from working, so I replaced it with a mechanical pull cable that sits just inside the companionway (so inside, out of the weather). I've been very happy with the positive mechanical cutoff.

 

[Ralph Johnstone]

I'm with you so far but I've got to know the purpose of the through hole in the bolt. As you say, no arrow on the bolt and if it IS a filter bypass, you could easily be passing dirty fuel on to your primary fuel filter without knowing it.

When looking at the above drawing, I become even more confused as there's no 120RMAM2 just the original 120RMAM. The centre bolt makes no sense other than it's purpose is to catch the centre threads of the spin on R12T fuel filter. The hole through the centre bolt must have a use, but it remains a mystery to me.

I seethe steel washer is shown in the Racor drawing so I guess it best to replace it when the kit arrives.

In the end, all that's important is that this thing filters the fuel and doesn't leak. One can only ignore the why's and how's of how the filter works. It's not for us mere mortals to know.

 

[RoyS]

Try bleeding at the injectors as you crank.

 

[jaysweet]

Try bleeding at the injectors as you crank.

I think I need to get the air leak (assuming there is one) sorted out first, though.

 

[Benny17441]

I started reading your post and was about to suggest that you look for fuel leaks; as where fuel leaks out usually air can get in. I read further and see you already found that out. The 2GMs are notorious for being difficult to bleed and often requires more than one bleed operation to clear any trapped air. Go ahead and bleed at the secondary fuel filter case and then at the high pressure pump to the injectors. If having difficulty consider utilizing a piggy back electric fuel pump.

 

[jaysweet]

I started reading your post and was about to suggest that you look for fuel leaks; as where fuel leaks out usually air can get in. I read further and see you already found that out. The 2GMs are notorious for being difficult to bleed and often requires more than one bleed operation to clear any trapped air. Go ahead and bleed at the secondary fuel filter case and then at the high pressure pump to the injectors. If having difficulty consider utilizing a piggy back electric fuel pump.

I'm hoping it will all clear up quickly once I fix the air leak, since my engine never needs bleeding after I change the primary. But maybe that's because I've never introduced air between the primary and the engine before. We'll see how it goes.

 

[jaysweet]

Regarding the stop lever. Not the problem:

 

[Ralph Johnstone]

I'm hoping it will all clear up quickly once I fix the air leak,

You're absolutley correct in your approach. Ignore EVERYTHING until you fix that one air leak.

In 24 years, I have ripped out fuel hoses, moved filter housings, and changed filters so often, I've lost count. And like yourself, I have never bled my 2GM20F once. It's probably passing so much fuel around the recirculation route, the small amount of air never causes a problem.

 

[jaysweet]

You're absolutley correct in your approach. Ignore EVERYTHING until you fix that one air leak.

In 24 years, I have ripped out fuel hoses, moved filter housings, and changed filters so often, I've lost count. And like yourself, I have never bled my 2GM20F once. It's probably passing so much fuel around the recirculation route, the small amount of air never causes a problem.

Well, that's just music to my ears....When I went out there today, after seeing that the fuel stop lever was not in the "stop" position, I put my time into other things (house battery upgrade, commissioning the fresh water system, etc.) while I wait for the o-ring kit to arrive. No matter what else is going on, I shouldn't be getting a fuel leak (and/or air leak) at the top of the primary filter. Why this leak chose to rear its head between Thursday's engine test (flawless) and Friday's engine failure (at launch), I have no idea. But most problems are not there until all of a sudden... they are. So over-thinking this is pointless, IMHO.

A couple of other points/questions. First of all: this is an 18-year-old boat. I have an 18-year-old Tundra pickup truck which has never given me much trouble, and I've never considered changing all the fuel lines. So I'm reluctant to plunge into this type of cure-for-a-dimly-understood-problem with my boat. I think the boat engine and fuel lines have led a much easier life than those in the pickup truck. Way less heat. Way-way fewer hours (the boat engine has maybe 400 hours total...). Others may have comments on this, and may well disagree. I'm interested in everyone's thoughts.

As for the hole in the "head bolt": it seems pretty clear that the top cap is divided into 2 chambers. The inlet chamber diverts fuel from the tank to the outside of the filter and to the bowl on the bottom (to let water settle and separate), while the outlet chamber has to have a way to get fuel from the center of the R12T filter. The hollow head bolt is that path: it screws into the center of the filter and guides fuel up and through the holes (that have been bothering you), where the fuel flow passes into the outlet chamber and on to the outlet fuel hose. In the re-designed Racor 120RMAM-2, I would imagine this bolt has been replaced by a hollow tube that serves the same purpose. I'm guessing the only difference is that in the new design, you have to spin the filter (with attached bowl) onto this tube just as you would with the bolt, except that you can't screw the bolt down right at the end. They probably made the change to save money in the manufacturing, and to avoid the possibility of leaks around the bolt.

 

[Ralph Johnstone]

Well, that's just music to my ears....

Ain't music your hearing, just the voice of reason.

First of all: this is an 18-year-old boat. I have an 18-year-old Tundra pickup truck which has never given me much trouble, and I've never considered changing all the fuel lines.

Not such a big deal, mine is a 24 YO boat. I changed out the fuel lines in the Nike shoe box about 5 years ago:

It gets bloody hot in there after the engine shuts down because the engine housing cooling fan shuts down at the same time. The hoses in there were hard and next they would be cracking. The hoses outside the Nike shoe box were in perfect condition because they were always cold as they lay on he hull. The only reason they were changed is because I was always looking for a better way to route them and change the filter to a more convenient location for a filter change.

 

[jaysweet]

Thanks for the the info, Ralph.

After wondering where my o-ring kit was, I ended up canceling the order, b/c it looked like it wasn’t going to get delivered any time soon. I ended up ordering a complete filter assembly. I really want to get it installed by next weekend. One big question: what type of sealant should you use for the 1/4” NPT fittings on the filter? Teflon tape? Pipe dope? If so, what kind?

I will have 2 plugs and 2 barbed fittings to seal up. Thanks!

 

[Capt Robbie]

try to hook up a fuel can directly to the secondary fuel filter fuel line to eliminate any issues from the engine. Then work your way back to the fuel pick up tube systematically. I just had the same issue last week. My cause was a broken hose clamp on the fuel tank pick up. Hose clamp looked good however the clamp teeth had a worn area allowing air into the fuel line. Stuff like this can make you go crazy.

hope this helps.

 

[Ralph Johnstone]

One big question: what type of sealant should you use for the 1/4” NPT fittings on the filter? Teflon tape? Pipe dope? If so, what kind?

The common industry practice for petroleum products in threaded piping 2" and less is several layers of teflon tape applied CW followed by a thin layer of Permatex #2 applied CW.

The tape must be wound CW otherwise it will not seal.

 

[jaysweet]

try to hook up a fuel can directly to the secondary fuel filter fuel line to eliminate any issues from the engine. Then work your way back to the fuel pick up tube systematically. I just had the same issue last week. My cause was a broken hose clamp on the fuel tank pick up. Hose clamp looked good however the clamp teeth had a worn area allowing air into the fuel line. Stuff like this can make you go crazy.

hope this helps.

That’s great advice: thanks. If things don’t go perfectly after swapping out the filter, I’ll take your advice.

 

[jaysweet]

The common industry practice for petroleum products in threaded piping 2" and less is several layers of teflon tape applied CW followed by a thin layer of Permatex #2 applied CW.

The tape must be wound CW otherwise it will not seal.

Thanks, Ralph. Lots of experience with plumbing and teflon tape. Not so much with diesel fuel fittings.