Didn't Find My Diesel Tank Slime - Ideas Why?

[rardiH36]

A few days ago, I posted about my 2QM20 quitting while in choppy conditions. I was unable to get it going again until bleeding the system. The fuel tank was 1/4 full -- lower than I had ever let happen before.

My post resulted in lots of good suggestions from the forum which I set about today.

First step was to use the in-line electric fuel pump to drain the tank of questionable contents. I even pressed an orbital sander (without the sand paper) against the tank in the hope that the vibration might break loose and mix up fuel crud/slime from the bottom of the tank. Also I tied a line to the end of my boom, routed it to a dock cleat and back to a primary winch. By this, I was able to heel the boat at an angle that put as much diesel fuel as possible under the fuel tank's pick-up tube.
All the way through the draining process the fuel into my containers was crystal clean. No sediment or slime. When the electric fuel pump stopped delivering even foamy bubbles, I took apart the Racor filter. Last time it was changed was 2.5-3.0 years ago. The element was very clean. The amount of slime on the bottom of the Racor clear plastic bowl was just a tad more than nothing. And no evidence of any water mixed in the fuel.

The Yanmar fuel filter on the engine had no sediment on it. Looked new. Its last change also was 2.5-3.0 years ago.

For the five years that I have owned my 1980 built boat, I've been reading about how organic slime formation, rust/sediment and moisture in the fuel causes problems for boat owners.

So where is my slime? Maybe my PO's have tended to keep the tank full which might have inhibited oxygen caused growth and rust? Or San Francisco Bay is generally a cool and low humidity environment that is good for tank hygiene?

Also today, I replaced all fuel hoses with new. Upon removal of the old, I found some previously unnoticed cracking/hardening. And also noticed that most of the hose segments were undersized 1/4" that had been forced onto the ~5/16" Yanmar engine and Racor fittings. So I installed 5/16" inch hose. And new Racor and Yanmar engine filters.

Upshot is that I didn't find the expected tank gremlins. But the engine failure did prompt me to get an important item crossed off the "to do" list. Feeling better about that!

 

[Steve Dion]

Rardi:

You know the issue with cracks in your fuel lines may be just what caused you problem. Once the engine starts sucking air it can be all over.

You are in a much better situation now that you have replaced and cleaned all of this stuff incase you have an issue again. At least you know that these things are no longer an issue.

Having a clean tank and good lines are an excellent start at a clean fuel system in the future.

Did you also change all of the nylon & copper washers? If you did not, you may want to do this before you consider the job finished!

 

[Jim Legere]

All the way through the draining process the fuel into my containers was crystal clean. No sediment or slime. When the electric fuel pump stopped delivering even foamy bubbles, I took apart the Racor filter. Last time it was changed was 2.5-3.0 years ago. The element was very clean. The amount of slime on the bottom of the Racor clear plastic bowl was just a tad more than nothing. And no evidence of any water mixed in the fuel...For the five years that I have owned my 1980 built boat, I've been reading about how organic slime formation, rust/sediment and moisture in the fuel causes problems for boat owners.

I think you are fortunate that good fuelling practices and cooler climate has probably prevented bacteria from ever getting a toehold in your tank. If you never saw it on your filter changes, chances are it wasn't there. I have had a similar experience here in chilly Nova Scotia: just a tiny bit of black sediment in the very bottom of the tank. I change my Racor every two years and there is very little in it. Now that you have changed you fuel lines and are aware of the "slosh factor" you will not likely have further problems.

 

[Ed Schenck]

Some of you will remember these remarks from times past. But many years ago I was reading here about all the problems with gunk in the diesel tank. So like a good scout I cut two big cleanout ports in my tank, one on each side of the baffle. And like Rardi I found almost nothing. Because the Cherubinis do not have a screen on the pickup tube I think any accumulatied gunk just gets picked up by the Racor.

P.S. I have never kept my tank full. Not summer and not winter. It was twenty years old when I opened it that one time.

 

[rardiH36]

Steve:

... Did you also change all of the nylon & copper washers? If you did not, you may want to do this before you consider the job finished!

Thanks. Yes I did consider replacing the washers on the various "banjo" fittings while at it. Best I can tell, all are copper washers on my engine. But the local Yanmar dealer in Sausalito wasn't answering the phone yesterday so I didn't visit them for the parts just in case they headed off somewhere. It is ski week! Got my fuel line hose, new clamps and replacement filters at the KKMI chandlery in Sausalito. Next time I am swinging by the Yanmar shop, I will get the washers and will do it sometime soon.

Ed and Jim:

Thanks the info that it is possible for even an old tank to be relatively gunk free. It's just that I read so much about the problem for many boaters I got the wondering "Where's My Slime?".

 

[Don12364]

Am confusled over why you thought you had diesel bug.

Surely, if your engine quit when the fuel level was very low and it re-started only after bleeding, then the end of the dip tube must have been uncovered from the fuel when the boat was heeling or rolling about and air had been drawn into the fuel lines and pump.
Was it not just a case of too low a fuel level?

 

[Johnb]

I too have found no dirt in the tank, or in the filters. We bought our boat in 1999 (3rd owner) and were told that 2nd owner had spent "all kinds of money" on the engine, tank and fuel system. He only owned the boat for maybe a year before being transferred out of the USA so perhaps we reaped the benefit. I have always re fueled by taking down 5 gal at a time, purchased at a truck stop.

After an incident like that I think it is wise to verify the whole system.

 

[rardiH36]

Hi Donalex and JohnB:

By keeping track of the plastic fuel jugs that I pumped my main boat fuel tank into, I have determined that the fuel I had remaining was about 7 gallons = just shy of 1/4 full. Really seems like a a sufficient reserve considering that each outing might use 1/4 gallon on average. But because of the engine failure, now I am alerted not to let the level get that low ever again because air suck will likely happen if heeled or bouncing around. 1/2 tank will be the minimum from now on.

My refueling practice has been similar to JohnB's. I stop by my town's Chevron station and fill my five gallon yellow jug with "land yacht" diesel. So much easier and for me safer than going solo into the tight marine fuel dock in Sausalito. Five gallons equates to approximately 20 outings so the practice is convenient. Because the road fuel is ultra low sulfur I do add an ounce of a lubricity additive for good measure. Although I do realize this is probably a "placebo" type of practice.

Donalex: As you suggested I was reasonably certain during my outing that my engine failure had something to do with the low tank level coupled with a lot of bouncing around = good chance of air suck. That's why my tactic was to anchor then bleed (and endure my wife's physical discomfort about the deviation from standard practice). But also, in the five years I had owned the boat, other than changing the filters once, I really had been ignoring my 30+ year old fuel system. The failure event prompted me to delve into it -- and ask for forum opinions. Part of the maintenance and investigation was to consider that maybe my tank had some of the frequently posted slime/bacteria/sediment gremlins. Seems that this wasn't the case. And hearing from forum members that their tanks also are free of gremlins helps a lot.

 

[Steve Dion]

Rardi:

Have you checked the length of the pick-up tube? It may have been cut short (who knows). I would get a measurement to determine how far the pick-up tube is from the bottom.

You can calculate how much fuel is below the bottom of tube by determining the cubic inches (231 cu in = 1 gallon).

None of this is really that important if you keep you tank topped off (I have run out of fuel a couple of times). There is nothing like running out of fuel going under the Golden Gate Bridge with an ebb tide and no wind.

 

[rardiH36]

Steve:

Interesting thought about the length of the pickup tube. But no, hadn't occurred to me to check. Also my guess doing the check will be a project in itself! Something that might be more important to know if I ever evolve a from SF Bay day sailor instead towards Baja bash cruising or more. But if that ever happens .... then instead a newer boat might be the preferred project!

 

[Steve Dion]

Rardi:

There is no reason not to take you boat out of the bay and head down to Pillar Point for the day. There are plenty-a-sailor that can join you for a trip out the gate and down the coast.

Life is short. Get your ass movin' and get sailing. You have a great boat that is more than capable of doing one of these short trips.

Hopefully your fuel problems are behind you. I would reconsider your battery issues but that is something that will come in time. A new charger will keep new batteries in tip top shape so this will NOT be your next issue.

 

[Benny17441]

If you used the in-line electric pump to drain the tank and were able to draw 7 gallons out of it the length of your pickup tube should be fine. Your fuel gauge seems to be on the money but always "trust but verify". That is an adequate amount of fuel to prevent sucking air under most conditions. Perhaps it had to do with the cracks found in the fuel line or some temporary obstruction. That is not a bad idea to always keep at least 1/2 tankful. Here in the warmer climates we get a lot of condensation and bugs in the fuel so it is pretty much standart practice when we motorsail and head out into open waters to have to replace the filters and purge the system underway.

 

[rardiH36]

Rardi:

There is no reason not to take you boat out of the bay and head down to Pillar Point for the day. There are plenty-a-sailor that can join you for a trip out the gate and down the coast.

Life is short. Get your ass movin' and get sailing. You have a great boat that is more than capable of doing one of these short trips.

Hopefully your fuel problems are behind you. I would reconsider your battery issues but that is something that will come in time. A new charger will keep new batteries in tip top shape so this will NOT be your next issue.

Steve:

Thanks for the motivational thoughts. I might not sail long distances or stay out for the duration, but we are out on SF Bay a lot. If the winds are good, it will be 2-3 times per week. Suites our style, available time and wife's like for the boat, but only if she isn't confined on the boat for more than 4 hours or so. But yes, Pillar Point has been on the radar screen. Also an over-nighter North to Drake's Bay will happen sometime in the next year or two.

Re the battery/charger, I think maybe you've tagged me for some other forum member's topic? On my boat, I've got two relatively new group 27 deep cycle batteries. And a backup emergency start AGM. A 20 watt solar panel routes into a recent vintage dual battery solar controller/charger. This is supposed to allocate the charging between the batteries "intelligently". Seems to be working. Every other week, I flip a switch which disconnects deep-cycle #2 from the controller and routes the charging to the emergency battery. For 110V source charging, about a year ago, I removed the original equipment ferro-resonant charger from the boat and replaced with a new 4 bank smart charger rated for marine use. (The wire for the 4th bank is neatly curled up since I only got three batteries.) But because the solar is working so well, and since my day sailing electrical demands are relatively light ... I haven't yet needed to charge my batteries with the 110V charger!