cleaning main diesel tank

[Ronar M]

Hi All,

I have to take the top off Ronar M’s main diesel tank to clean it out. Has anyone done this? My main question is whether all those bolts holding the access hatch on are captive. Once I get the nuts off, will the bolts fall into the bottom of the tank or are they welded or glued in place. I guess they must be because it’s impossible to get a spanner on them when tightening the nuts but I would appreciate confirmation before I start.

Cheers, Trevor

[Moderator]

Hi Trevor – yes, we have cleaned our fuel tank. We were also scared of the bolts falling in. It did not happen. Removing the lid was relatively straight forward. The two biggest problems were:
1. how to pry off the cover once the bolts were removed (just took patience and persuasion.)
2. How to get a new gasket. We had a diesel mechanic make on for us from cork sheets.

A word of caution – do not lose any of the nuts as you take them off. They are BSF threaded, and so replacement is not straight forward! Fortunately, we could reuse all of ours.

We have a posting on our experience here. The photos at the bottom of that page will be interesting for you. Click on the i icon just above the photo to be able to read the caption that explains what you are seeing.

Be glad to answer any more question if we can. This task was definitely worth the effort – our tank was filth! I strongly recommend – just do it!

Marilyn and Van

[Moderator]

Ah – one more thing, Trevor. When we cleaned our fuel tank, we had about 20 gallons diesel. So we paid the mobile fuel polishing service several hours of wages as they filtering all that diesel. They also charged us for several expensive filters. I think he went through 3 of them. End result was maybe US$500 or more was spent on keeping that 20 gallons of diesel. That didn’t make economic sense.

You might consider starting with not much diesel, and plan on discarding it. Scrub the bottom of the tank, then siphon out the gunk and diesel together and discard it all. If you don’t bother filtering the gunk from the diesel, you might save some money.

Not sure who will clean tanks that way, or how you might get rid of dirty diesel in an environmentally responsible manner – but it’s something you might consider.

Marilyn and Van

[Ronar M]

Hi Marilyn & Van

Thanks for that. I have already pumped a lot of filth out of the bottom using a pump on my electric drill and clear tubing so that I could see the dirt. Now that Ronar is ashore and no longer stirring up the sediment I plan to pump off the top (hopefully clean) fuel before going for the sludge. I think the auxiliary wing tank is ok but plan to let the fuel from this into the main tank once the latter is down to the dregs, let it all settle and then repeat the procedure before taking the top off. I friend has a motor factors company and says he can get cork gasket material so I’m ok there.

Cheers, Trevor

[Ronar M]

Hi Marilyn & Van

Job done and with the minimum of grunting. Am aboard Ronar M at the moment. Will write a longer account to help others when I get home. Trevor

[Ronar M]

Hi All

I found cleaning out the tank reasonably easy but there were a few sticky bits which I will relate in the hope that it will help others. I easily loosened the small unions on the top of the tank (fuel feed, fuel return and a third pipe of unknown function)and either pushed away or bent away their copper pipes) That left me with the half inch(15mm)breather pipe and the large (2 inch?) filler pipe. The unions came undone easily but the pipes would not move. A glance in the engine bay revealed a union on each pipe which would break the pipe and allow their removal. The breather pipe union came undone easily but the union on the large filler pipe was right in the forward port side corner of the engine bay (where the outlet from the wing tank also joins it). This was a swine to undo and took ages and lots of WD40 (whilst lying on my belly with my feet in the air in the saloon). It has a large nut requiring a very large wrench and the handle of this had to be negotiated round various obstructions in the engine bay, not least a hot water calorifier which I have fitted on the port side of the engine. Once this was off and the pipes moved I could lift off the top of the tank – I had previously undone the ‘n’ nuts which hold this on. There are two long copper pipes on the underside of the lid so be careful when lifting it off. The inside of the tank was well gunged up – a thick layer of black sludge on the bottom and sides as well as both sides of the tank divider. I used a wallpaper scraper taped to a short piece of wood to remove this and decided to scrape upwards rather than downwards to prevent even more sludge from accumulating in the bottom. I had left a gallon or so of fuel in the bottom and I stirred this vigorously before pumping it out . The pump coped reasonably well but finally blocked up leaving about 2 pints of fuel and sludge in the bottom. This I removed with an old polythene box. Last of all I used an old sponge to wipe down the walls of the tank and to soak up the residue in the bottom. I found the wallpaper scraper on its handle was helpful for pushing the sponge around and retrieving it from the tank each time it needed squeezing out. The tank was now bright and shiny – just like the day it was made. There was a thick rubber gasket under the lid which stayed on the top of the tank throughout. I cleaned it up and put some jointing compound on it before bolting down the top and reconnecting the pipework.

Note that previously I had sucked fuel out of both tanks using clear pipes so that I could see what was coming out. I taped a length of wire to the pipe so that it was stiff enough to move around the bottom of the tanks. A lot of black sludge came out of the main tank but none from the wing tank. I think if any sludge formed in the wing tank it washed into the main tank every time fuel was moved from it to the main tank so I have not bothered to clean the wing tank. Also I think that being fibreglass it will not produce as much condensation as the stainless steel main tank so there was probably never enough water in the fuel to let ‘the bug’ flourish. Cheers, Trevor

[michael bennett]

I have installed a fuel polisher (diagram avaiable to email) which pre cleans fuel and returns to tank, so very clean fuel to primary double filters. It also enable bleeding when filter change time, which is now double the time it was and they are still very clean filters, but I change anyway, the 12v pump can be switched both for bleeding, saves those indents in thumb from pumping fuel pump, and the return from the polisher can be redirected to feed primaries if mechanical pump fails, I have fitted a new one and kept the old for a spare anyway. Pump works when engine starts, and can also be swiched on when in marina or at anchor.
The cause of all this protection was the result of a engine stop, yes dirty filters, in a busy seaway just outside Santa Teresa di Gallura, Sardinia, with ferries giving me 5 on the horn! no wind, and trying to change the filters with them roaring past and me slopping in the wake, not want to repeat that again. The cause was a fuel load taken on there, I also now use a filling funnel http://www.asap-supplies.com/green/fuel-filling-funnels like that which protects from dirt and water from the provider. Hope this helps, I know Marilyn and Van have done something similar.

[Moderator]

Hi Michael (aka angelsson) –

Yes, we have installed a fuel polishing system, but yours seems more clever because it can do double duty. Ours just polishes and returns to the tank. I would be very interested in seeing your diagram. Pls email to me at Rainshadow(at)driftwoodkey.com – just replace (at) with @.

The details of our fuel polisher are described on our blog here.

Cheers – Marilyn and Van

[Author]

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