OT - Need to diagnose fuel tank problem.

[NJ-JOHN]

Thanks in advance for any advice. I presented my problem here because I've gotten solid information from the Grady members and dont know where else to go.

My parents have picked up and moved to FL. to be near my sister, with them is a 17" Cape craft with an ongoing fuel system problem. I am flying down tommorow to hopefully get to the bottom of things. The dealer in NJ where the boat was purchased insists the water in the fuel is from the pump. They have made several attemts at convincing my mom that there is no problem with the boat, but rather the fuel. From what I gather the problem is on the boat.

I've assembled a fuel pump with fittings and alligator clips that I will use to remove the water from the fuel tank. After that I will need to locate the leak, which I believe to be topside of the fuel tank. I am bringing some tools, but will need to improvise others upon arrival.

What is the easiest way to presurize the tank? I think that will be my first step in determining where the water is coming in.

 

[richie rich]

first of all, describe this fuel pump with alligator clips...sounds like you can cause yourself a spark somehow which is really not a good thing to do around fuel....the clips and battery source better be far away from the open tank if thats how you are doing it. Secondly, how did a water problem become a fuel leak problem? If you have a hole in the tank, that means it either rubbed somewhere or it corroded over time....in either case, the tank should be emptied, flushed with a water solution and removed for either a welded repair, or complete replacement.......you can try doing an epoxy repair, but its not a long term fix and if you're having fuel/engine problems, you are probably getting bits of debris from a failing tank that will clog your carbs or injectors and it will keep clogging if that tank remains after a quickie repair. Pressurizing a fuel tank isn't very safe if there are any fumes or fuel remaining, so it should be thoroughly flushed, plus you'll have to plug every inlet, vent, fuel line etc to do it. With a proper exterior clean up, you should be able to spot a hole in the tank without the need to pressurize it. If the boat is only 17 feet long...its a relatively small tank to go through.

 

[Amigo]

First question. Does this boat have a fuel filter??? If not, one should be installed. It should be the fuel/water separator type.

In my mind it would be very unlikely that water would be leaking INTO the tank without lots of gas leaking OUT. You would certainly smell the leaking gas.

With what you have told us I would agree that you have some bad gas. I would buy a length of clear plastic hose and syphon rather than use a pump. Less chance of going BOOM.

 

[BobP]

If he knows what he's doing , he can pressurize the tank to 1-2 psig and hold it, to see if it leaks down. That's presuming the tank was manufactured to 4 psig by spec.

Have to plug the vent and fill lines, can add pressure via fuel pickup.

As far as water getting into fuel, most likely bad fuel dump from station or leak at fill fitting.

However, water can also enter via bad gasket at level sender flange and you won't smell it, when water can collect and sit on top of tank around flange.

 

[richie rich]

Well, thats the $64,000 question....but if you think about it...why bother pressurizing a gas filled tank that will pump explosive fumes into the bilge area, when you can really inspect the rub areas, fuel fill areas and plain old corrosion areas with out the need for fuel sniffification (is that word worth a trademark ......I just don't think you need to go that far to determine a leaking problem......pay attention and use common sense and you won't have to do that...