My engine is very light on fuel so I prefer to fill a 20 ltr drum at the servo rather than top up at a marina. I also
use FTC as an additive which I put in the drum prior to carting it to the boat. I use the recommended amount ( quite
miniscule ).
Last week I changed the CAV fuel filter cartridge and in the separator was a pool of dark brown liquid that looked
awfully like FTC. There wasn't a great amount (maybe an eggcup full ) it lay at the bottom of the separator so it was
heavier than diesel.
So does this mean that FTC does not fully mix with the diesel fuel or is it that the CAV filter can separate the two. When
I swirled the separator around before I emptied it there was no sign of it re-mixing. Or was it some other substance
entirely ??.
Betting not FTC but water.
An egg cup is quite a deal though.
With your CAV filter do you reverse it against the instructions
Sam
I've just had a similar issue. I do have some water in my tanks which does come into the filter now and again. I also had a brown layer that sat between the water and the diesel. And I thought the same as you. So I have a contact in the chemical industry who had supplied me with a fuel additive to deal with the bug. He told me the brown layer is the bug. I need to dose the fuel at a higher dose to eliminate it. I was given the additive complementary so it is not as though he is looking for more sales.
Scrubby
Thanks guys. Lydia, I'm not aware of not fitting it properly if that's what you are alluding to, it's all air tight and ship shape.
Scrubby. I only have a small tank ( 40 ltrs ) with no inspection hatch, so if there's something in it I wouldn't know, However,
you're experience suggests I might need some medicine for it, so what was the additive you used ?.
Sam, I use a Pela oil extractor which i use to pull samples of fuel from non accessible tanks. Some tanks you can easily get all the muck out with one
I was getting some gunk and staining in my filter. I'd previously used FTC 'shock' and maintenance treatment, and thought my tank should be ok. I pulled the tank out and took it to a tank fabricator for steam cleaning. Result = lower third and base of the tank was covered in 2-3mm of degrading brown gel. It had a baffle in it and he'd never be able to steam clean it properly. I opted for a Diablo plastic tank. You can see fuel level, and there's a good size cover for cleaning access if needed. No more fuel contamination.
Right.....I'm not liking the sound of this. My tank is accessable albeit an awkward job to remove. If I do remove it, what's the
best course of action ??.
Select to expand quotesamsturdy said..
Right.....I'm not liking the sound of this. My tank is accessable albeit an awkward job to remove. If I do remove it, what's the
best course of action ??.
Sam, I was in a similar situation a few fears ago, the only direct access to the tanks was via a fill fitting installed directly to the tank tops, (not the deck fill ) and I ended up making up a high volume fuel polisher that I have used regularly with great success, no more gunk to fill fuel lines and filters. 
Wasn't cheap but oh so worthwhile.
SAM
Don't panic, go to Repco and buy a carton of CAV filters, there are very cheap by the box.
Give it a chemical dose with fresh fuel and just change the filters every say 3 hours then 5 hours.
Then keep the tank very full over periods of high humidity.
As for the CAV. Filters they are not marine filters and so the water trap is after filtration so old timers often reverse the flow so the water comes out first so nothing for the bug to grow in in the bowl.
You do this by reversing the inlet for the outlet
Select to expand quotelydia said..
... so old timers often reverse the flow so the water comes out first so nothing for the bug to grow in in the bowl.
You do this by reversing the inlet for the outlet
What a pointed comment, never knew that thanks Lydia.
With fuel flowing in reverse through the folds of the filter element, do you know whether that appreciably increases the flow resistance ?
For 100HP engines it would not matter, but for 1/2 cyl diesels, is that an issue at all (asking out of ignorance) ?
Don't Panic.
Oh well. Lydia beat me to it.
You have gunk (Bug) in the bowl of your fuel filter,
That DOESN'T mean you need to remove the tank and buy a new one.
It means the filter is doing its job.
For information about the gunk.
en.wikipedia.org/wiki/Microbial_contamination_of_diesel_fuel
Get a 12 volt self priming pump. This pump is what I use to pull the engine oil out when I do a change.
www.aliexpress.com/item/32831034001.html?spm=a2g0o.productlist.0.0.21c636179hy2AV&algo_pvid=9a8c1844-c711-49ef-a595-a82f4b0af741&algo_expid=9a8c1844-c711-49ef-a595-a82f4b0af741-0&btsid=93512471-24f6-4b15-b7f7-5ec97fb3b024&ws_ab_test=searchweb0_0,searchweb201602_4,searchweb201603_52
Turn off fuel cock if it comes from the bottom of the tank
Fit a hose that goes to the bottom of your tank.
Pump out from the bottom into old 2 litre coke bottles until you get all of the water and gunk out.
Hopefully there is not much.
Now you have no water in the tank.
Remove all of the fuel in to Plastic 18 litre jerry cans.
Now you have an empty tank with a small coating of gunk on the walls of the bottom most section.
Leave it that way for as long as you can. You are trying to kill the bug by altering the environment in the tank.
Add 10 litres (or so) of fuel and load up with you favorite treatment.
Leave for as long as you can ( a week or so)
Pump out or drain the fuel and you should be back in business.
I have never heard of Lydia's reverse flow fix, but it sounds like the way to go to ensure a clean fuel future.
Now, if initially when you pump out the tank and end up with (pretty) clean fuel, it will be as Lydia suggested.
You only have bug in the water bowl to deal with and that is simple.
All the best
Gary
Select to expand quotegarymalmgren said..
Don't Panic.
Oh well. Lydia beat me to it.
You have gunk (Bug) in the bowl of your fuel filter,
That DOESN'T mean you need to remove the tank and buy a new one.
It means the filter is doing its job.
For information about the gunk.
en.wikipedia.org/wiki/Microbial_contamination_of_diesel_fuel
Get a 12 volt self priming pump. This pump is what I use to pull the engine oil out when I do a change.
www.aliexpress.com/item/32831034001.html?spm=a2g0o.productlist.0.0.21c636179hy2AV&algo_pvid=9a8c1844-c711-49ef-a595-a82f4b0af741&algo_expid=9a8c1844-c711-49ef-a595-a82f4b0af741-0&btsid=93512471-24f6-4b15-b7f7-5ec97fb3b024&ws_ab_test=searchweb0_0,searchweb201602_4,searchweb201603_52
Turn off fuel cock if it comes from the bottom of the tank
Fit a hose that goes to the bottom of your tank.
Pump out from the bottom into old 2 litre coke bottles until you get all of the water and gunk out.
Hopefully there is not much.
Now you have no water in the tank.
Remove all of the fuel in to Plastic 18 litre jerry cans.
Now you have an empty tank with a small coating of gunk on the walls of the bottom most section.
Leave it that way for as long as you can. You are trying to kill the bug by altering the environment in the tank.
Add 10 litres (or so) of fuel and load up with you favorite treatment.
Leave for as long as you can ( a week or so)
Pump out or drain the fuel and you should be back in business.
I have never heard of Lydia's reverse flow fix, but it sounds like the way to go to ensure a clean fuel future.
Now, if initially when you pump out the tank and end up with (pretty) clean fuel, it will be as Lydia suggested.
You only have bug in the water bowl to deal with and that is simple.
All the best
Gary
I bought one of those pumps for oil extraction. I ran the engine for maybe 10 minutes to warm the oil up but the oil was still too tjjck for the pump to easily suck it out.
How long do you run your engine before changing the oil, do you get the oil nicecand hot?
Select to expand quoteKarsten said..lydia said..
... so old timers often reverse the flow so the water comes out first so nothing for the bug to grow in in the bowl.
You do this by reversing the inlet for the outlet
What a pointed comment, never knew that thanks Lydia.
With fuel flowing in reverse through the folds of the filter element, do you know whether that appreciably increases the flow resistance ?
For 100HP engines it would not matter, but for 1/2 cyl diesels, is that an issue at all (asking out of ignorance) ?
Dont do it, reversing the flow stops the way the filter is designed to stop water particles flowing on to the pump. Best to install a separate water trap if needed.
HI MB.
I can do an oil change in 30 minutes or so. I usually do it after a day out and take the oil home with me.
So maybe 45 minutes, but I have an old YSE 12 and they don't run hot at all.
The oil pumps out slowly (and it takes maybe 5 minutes for 2 litres) because the hose is a small diameter but I get nearly all of it.
gary
The fuel tank pick up will not usually be right at the bottom so that sediment is not sucked into the fuel system. Water will always accumulate there. If you have access to the top of the tank use an oil extraction pump fitted with some plastic hose and a length of copper pipe so that you can poke it into the corners of the tank and suck it up. I use one of these.
www.ebay.com.au/itm/12V-Oil-Extractor-Pump-Diesel-Fuel-Transfer-Suction-For-Car-Boat-Engine-Electric/173920839120?hash=item287e7d65d0:g:lXMAAOSwcw9c82Dd
I removed my Cav filters and made a fuel polishing system but with only a maximum of 40 litres it's probably not worth messing with. Just dump the old fuel. Change both primary and secondary fuel filters once a year and drain off the water from the clear bowl when it accumilates.
Select to expand quote
Ramona, I suppose bad things will happen if you try to use this pump to push diesel through a coarse CAV filter at the same time as transferring - throughput rate too high ?
What will happen - pump just grind to a halt, or just keep spinning but overheat ?
Select to expand quotesamsturdy said..
Thanks guys. Lydia, I'm not aware of not fitting it properly if that's what you are alluding to, it's all air tight and ship shape.
Scrubby. I only have a small tank ( 40 ltrs ) with no inspection hatch, so if there's something in it I wouldn't know, However,
you're experience suggests I might need some medicine for it, so what was the additive you used ?.
Sam
The additive is from Wildcat Chemicals but the type is immaterial. There are two types of additive which would take too long to go into here. The point is that you need a higher dose to kill the initial bug then reduce it to a maintenance dose.
The two common fuel additives I know of Fuel Doctor and Diesel Power. Both are good products but Diesel Power will absorb water in suspension if you overdose and make the diesel cloudy. Not sure if it adversely affects the engine but I'm told this is good. Fuel Doctor on the other hand makes some claims which don't make sense to me but at the least it is an effective biocide.
I see in a later post a recommendation to reverse the flow direction of the CAV filter. Doesn't gel with me as the CAV filter is an agglomerating filter. Won't work properly in reverse.
Finally i run a small fuel pump from ebay see below. Normally turned off I run it to prime the system after changing filters and also to polish the fuel when I worry about water in the tanks.
Its a pretty involved subject. I've learnt by trial and error. Best thing is to keep water out of your fuel and have a clear bowl that you can see the condition of your fuel.
regards
Scrubby
www.ebay.com.au/itm/AU-Electric-Fuel-Pump-12-volt-Solid-State-4-to-6psi-130-LPH-Petrol-Universal-Car/251958325212?epid=726717192&_trkparms=ispr%3D1&hash=item3aa9e2efdc:g:3~8AAOSweu1cwmBE&enc=AQAEAAACMBPxNw%2BVj6nta7CKEs3N0qVXN%2FQXStSv%2B95%2BUVFmROrTNRBKUwSsdB0Ihi2p2oA78QzGZZuDPlaIse3MNhRb0bATqHpmjFeoO%2BissZS4x3XV6rx8vKnlxkTngZ2cbMVTVvMIqzC1akHhxBlMAHlq53okey37iyXkD3eF5hxD%2B08BmEsyZ1xVimAJ%2BaDJ9My%2F%2B00dRSoDOE7sbVlKk4ulOu0wmwILGH%2FZw0PbNs%2F6w2wO06arYHkkhdUe22miOwUX21j%2FDBkSFb97%2BRc04nASdBwX%2FqnbyAxiOFUUU%2FG252fEqVBMbfvunlDPJ32aix19tDuJ82xgiY%2BWLTjWDLkRjZxBvUDGWfptFk1YBBg4hsj0n1V4H4Zlo0Cr576E2txy7y7LN50YMK0U2CfKekIAlDVuyJVM2xRcxiNupzgkQoE5jra1lL6B2Viacm1txU%2FXAZh%2BGSX1Tz3UKPEHqaJGbF00%2FaFjQMkVvKxWAX33Ea4URDBm5goCY87UgW%2FGkyFHVniy8diBZCN5gu6F5wFStWYPwS3dkXFetgmMls2LECTp0s61WZH0jsZE%2FglJ83JgUZBC3TE%2Fq5uPvbvvZe26b6MVTWClyaFJ75KHHMm8niDfbSDY7yh5jPC4mjTMpkh5HrMxhRDzL%2BTzUCmgVp9RMe2Rl8eHbq89v%2BNTJwP7PnLS%2FDXQAic96UelJ1EWOOmuCvUWOHbq1Rx9pB6S3EQCIKhzNyyWLSG7%2BsGVR3dS48MR&checksum=251958325212bc24f54e14c647f7a24e65219623ef35
And while this thread is adrift, I've been using an eBay version of the Pela vacuum to change engine oils in the family cars ( hot or cold ) ( diesel and petrol) transmission on the little ship as well as suck up bilge water/spills. Have used it to clean a yachts keel moulded fuel tank. It's a great bit of kit.
Sam, for my two bobs worth, install a dedicated water trap and change the cav filter regularly, and use the vessel as much as possible. Big problems happen in systems that are left idle for long periods.
Thanks fellas.
I use my boat regularly, It's never left for more than two weeks and I try to get down every week.
I also endeavour to keep the fuel tank pressed and fill it when it gets to half empty. This is the first
time there has been an indication that there is a problem and I want to get on top of it. An additive
seems to be the easy way to go, maybe Diesel Power that Scrubby has suggested, I guess all the
instructions are included so I should be OK.
Select to expand quotesamsturdy said..
Thanks fellas.
I use my boat regularly, It's never left for more than two weeks and I try to get down every week.
I also endeavour to keep the fuel tank pressed and fill it when it gets to half empty. This is the first
time there has been an indication that there is a problem and I want to get on top of it. An additive
seems to be the easy way to go, maybe Diesel Power that Scrubby has suggested, I guess all the
instructions are included so I should be OK.
The FTC you are using does the same job as Diesel Power.
