G'day all,
I have had an ongoing issue with a fuel tank in my boat. This has been going on for a fair while, albeit intermittently, but it has finally done my head in and I am going to do something about it and just want to put it out there to see if anyone can think of something less drastic or think of a different reason for the symptoms I am experiencing. Also, I am not going down the path of 'warranty' or 'fit for purpose' talks, I am at a stage that I have had enough and will just fix it myself as I dont want to draw it out and am not in the game of slagging people who installed it.
Approximately 18 months ago I had one of my fuel tanks replaced as I had an electrolysis issue that caused a small leak. Rather than muck around repairing the tank, I opted to replace it as the effort involved in cutting the sealed deck, removal of the tank and refit/ relay of the deck seemed too much to replace with anything but a brand new tank.
From the outset I had an issue. From time to time the motor being fed from the new tank starves of fuel periodically, getting worse and worse until such a time I turn that motor off and get home on the other one. At the start I replaced all filters, fuel lines and fittings from that tank and found a small part of the line that had minor delamination. Bingo!! Problem solved!! But it wasn't to be..... after a period of time ( a couple of months later and any number of tanks of fuel) it happened again. Followed the same process, problem disappeared for a while. At this stage I changed the tanks over with a cross feed and had my starboard motor running off the port tank, and vice versa. I did this to work out if it may have been an infrequent motor issue, basically if I could get the other motor to behave the same way, I would know it was tank related. After a while I gave up on it, I was sick of the fuel lines on the deck, but nothing happened until I changed them back then the original problem came back, and after changing them over again I finally made the other motor starve of fuel so knew it was the tank and not the motor.
Now when the problem occurs (as I stated there can be months between occurences), if it happens once, it will invariably get worse and worse and it doesnt take long before that motor is useless. In between occurences the motor runs fine with no hassles. Last time it happened off the Breaksea, we were ready for it, waited until it was unworkable, then cut the fuel line and ran it out of jerries for the trip home. We went from Roonies to Urangan with out any hassles at all running out of the jerries.
This is what I believe to be the problem. I think there is something non dissolvable floating around in the tank. How it got there, or was left there, is anyones guess but I think it floats around for a random length of time, and eventually gets caught in the pick up, and once it is there, it stays there until the boat gets refuelled or it moves around while travelling or something, boat goes good for a length of time until it finds its way back to the pick up.
The breathers are clear and not blocked. There is no air getting into the system, I have checked but not replaced the lines laid into the hull channel, but I would think that if it was entraining air the problem would be more ongoing and no way you could go months at a time without it arising again. Its not the motor, as I said we can make both motors do the same thing when running off that tank and it will run perfectly out of a separate jerry after being unusable when the problem starts.
This is what I am going to do. I have a guy with a big petrol sucky thing coming around next week. I have made up a spear that can go to the bottom of the tank thats much bigger than the pick up to quickly drain the tank and hopefully pull something out of it. He is happy to drain it and fill it up a few times in the hope of dislodging something and we will run it through a sieve so we know if we catch it. If that doesnt work I am going to drain the tank, 'defume' it so to speak and cut through the deck and cut a hole in the tank to physically inspect it. This is obviously a worst case scenario, as it does bring with it a job to fix the boat and some risk (although I will mitigate that). I will then reseal the tank with a sender unit. Should I find something in the tank I will remove it, but with the size of the baffles I would have to be lucky do cut in the right compartment of the tank, if I find nothing, I plan to drill holes in the pick up, that way if the object does block the pick up, fuel can still be drawn through the holes.
Sorry for the long winded post, but in this one I feel all the information is relevant.
Am I right in suspecting something is in the tank?? If not, what do you think is the problem??
Are my methods for addressing the problem right, wrong, or plain silly? I am very open to any ideas at this stage.
It is a very random problem, and very annoying. It can happen on a full tank, half full tank or a near empty tank. There is no vacuum lock or anything involved, if there was I would assume there would be a hissing noise when I crack the fuel cap when the problem happens, also I have checked and rechecked the breather and it is fine. It is a 340 litre tank, but I dont think this is a problem to do with size.
Any ideas, solutions or general musings to help fix this issue would be greatly appreciated before I wield my holesaw.
Cheers.
Maybe not relevant, but on my smaller boat I got a related problem where my donk would die at high revs but was OK at low speeds.
In my case turned out that when I fitted the fuel filter I made one hose too long and it kinked under way.
Enough fuel got past the kink for low speed work but not for full bore.
Hope you sort it out.
My other fuel problems were caused by the "servicer" not changing the fuel filter under the cowl, that ruined my original motor.
Shane, to prove if something is blocking the fuel pick up, try and stick some stainless wire (Tig rod etc) so that it is protruding into the tank and reconnect your fuel line with the wire still inside. Make sure the wire has enough length to not come back out up inside the pick up pipe and negate the test. This should prevent anything from completely blocking off the fuel pick up whilst testing.
one of those flexible inspection cameras might be able to help to look inside the tank?
Hi littlejim, that thought crossed my mind too so I went and bought some 90 degree elbows and put them in the lines instead of having any curves. Wardy I like that idea, that could even potentially work in as a more permanent solution as long as the object is not a rag or something that can cover the lot. I like the way you think, its not something I thought of. I still have the old tank thats exactly the same so can work everything out using it and get rid of it as scrap...
Hi PROS, we thought of that too and its an option once the tank is empty. Nobody could tell me if they are intrinsically safe but I would assume they are since they use them in sewers. Just not sure if one that was long enough would fit between the baffles and the sides of the tank but its certainly an option.
Shane I would be careful too with the I.S issue. the only one i'd use would be with a fibre optic extension. But it would be the only way to know for sure.
Mate it might be more trouble than it's worth but see if someone in your are will do a Bore a scope inspection for you.........They are I.S as we use the offshore frequently to do valve and pipework inspection........Maybe a longshot but it could be worth a try.
Dan
Confidence.......the feeling you get before you fully understand the situation.
Is the primer bulb getting sucked flat?
Yes it is mate. But I have replaced it five times in an effort to make sure the solution is not the most simple one. I did get a dud primer bulb, thought I had it sussed, but it happened again
Can you blow back through the line and see if there is any restriction?
Shane,Originally Posted by ShaneC
The dramas live on!!.
When you say checked the lines laid in the hull, what exactly do you mean? Can you connect a new line to the tank itself or is there absolutely no access. If these are original lines, are you sure that is not where the problem remains, like if they were slowly delaminating internally or something.
When it does happen, what do you do to make the problem go away? Just give it time before the next trip out?? Have you ever solved it in the water, as in after some time, it has run ok later in the same trip, without redeveloping the problem?
When you simulated the problem on the other motor how much of the problem tank setup and plumbing remained in use, (ie. just the tank and the original line in the hull, or was it fed form that complete system, filter etc)?
Exactly which bits remained in use when connected to the opposite motor?
If it was an airlock, you would expect it to be solved (temporarily) as soon as you crack the filler, so you would have to assume not that issue and thus nothing related to the breather.
You never had these issues before you changed to the new tank did you (from what I recalled)?
A flat bulb indicates a fuel restriction so you are on the right track.
Hey Perko. Yep can blow back into the tank with a lung full of air and blow bubbles with no hassles. Darren, mate I have pressurised the tank without any air leak so I am confident thats not it. When we cross fed the tanks.. my set up goes from tank to filter to motor. I made up some cross feeds (I actually had them in case a motor went on the last day of a big trip so we could draw fuel from both tanks in an emergency) that gave fuel the same way just on the other motor. Its not a dangerous problem now that I know how to get around it but I feel its something I certainly dont need, especially if I make the effort to drive to Agnes or Bowen and it happens on the way out......
And the inlaid fuel lines are not rubber
Posting Permissions
Reply With Quote