The dreaded fuel leak

kwaltersmi · June 04, 2015, 06:17:16 AM

I went to the boat yesterday to check on her and refinish the exterior teak. I did my usual bilge inspection and was very surprised to see the bilge filled with about 3-5” of diesel (maybe 2+ gallons?). Yikes! The oil rag/pad I keep in the pan under the engine was also saturated with fuel. I did a quick look around and didn’t notice any obvious sources for the leak. I looked at/felt the fuel filters, bottom of the engine, most of the fuel lines and the bilge area under the head sink. Nothing noticeable. Maybe the leak only occurs while the engine is running?

The boat has been sitting in the slip for the last 2.5 weeks since I’ve been busy with life. The last time I was out (2.5 weeks ago) I changed the fuel filters and went out for a 3 hour sail. I peeked at the filters while sailing and didn’t notice any leaking at the time. However, I did see a clear wet streak on the inside of the hull coming down from behind the fuel tank shelf. I didn’t think much of it at the time and figured it might actually be a water leak from a stanchion or the hull/deck joint since we had had a lot of rain. The streak was gone and/or dried when I looked at that area after discovering fuel in the bilge yesterday. Now I plan to pull the panel in the aft cabin and closely inspect the fuel tank, shelf and fill/vent lines. I wonder if the tank itself could be leaking or perhaps one of the hoses going to the deck/transom.

Per my research here, I’ll do a more methodical search and inspection on Friday including looking at all fittings, fuels lines, fuel pump, fuel filters, etc. I also might try to unscrew the fuel filters and put them back on to be certain I have a good seal and proper fit. Just to be clear – Is it ok to start the engine to look for the leak? I noticed several threads on here suggesting an inspection with the engine running, but this wasn’t intuitive for me.

I soaked up as much of the fuel as I could with oil rags and then pumped the remaining leaked fuel and water out of the bilge with my manual dinghy pump and put it in a container for proper disposal later. I also shut off the fuel via the petcock on top of the fuel tank. I’m not sure what to make of it if there’s more fuel in the bilge when I return on Friday. I suppose it means either something on the engine is leaking or the tank itself is leaking since the petcock is closed.

I realize y’all can’t diagnose a leak from my description above, but I thought I’d post anyway to see if there’s anything obvious I missed or should do as a next step. Thanks!

Stu Jackson · June 04, 2015, 09:18:23 AM

Sounds like a methodical approach. From what you've described, the fuel tank seems the most likely culprit. Good luck tomorrow.

chuck53 · June 04, 2015, 09:30:17 AM

I know a guy with a C36 and his tank did leak and it leaked into the aft cabin. He really had a mess on his hands. If I recall, he had to replace his mattress.

Stu Jackson · June 04, 2015, 09:38:41 AM

www.pureayre.com is great for getting rid of any smells.

kwaltersmi · June 04, 2015, 09:46:18 AM

Quote from: Stu Jackson on June 04, 2015, 09:18:23 AM
From what you've described, the fuel tank seems the most likely culprit.

That's my number one bet too because of the streak I saw on the aft port hull side while looking in from under the head sink. However, I'm hoping it's something really easy and simple like a misfit fuel filter or loose hose clamp. I really don't want to deal with a project the size of replacing the fuel tank.

If it is the fuel tank, I'm not sure how the leaked fuel reached the pan under the engine since it's basically closed on the sides and rear and only open to the bilge via a small drain whole forward.

Stu Jackson · June 04, 2015, 10:24:22 AM

Quote from: kwaltersmi on June 04, 2015, 09:46:18 AM

If it is the fuel tank, I'm not sure how the leaked fuel reached the pan under the engine since it's basically closed on the sides and rear and only open to the bilge via a small drain whole forward.

Coulda run down a hose or a wire.

Good luck, still.

KWKloeber · June 04, 2015, 10:58:59 AM

Chuck,

Shouldn't be an issue running the engine and looking - first get some paper towels or absorbent pads or flat container under the suspected leak spots, could even tape something in place to catch runs. I hate to ask - was your bilge pump working!?!?

ken

kwaltersmi · June 04, 2015, 12:09:50 PM

Quote from: KWKloeber on June 04, 2015, 10:58:59 AMI hate to ask - was your bilge pump working!?!?

The float switch was up and the pump was switched on on the fuse panel, but it was not pumping when I arrived. I'm assuming the pump automatically shut off because of the diesel. Or it was ruined because of the diesel. I don't know how long the fuel was in the bilge since it had been 2.5 weeks since I had been at the boat.

I turned it off when I was pumping the fuel out of the bilge but then turned it back on afterwards and it made the normal sound but didn't pump much of the water I put in to try it out so I hand pumped the water into a bucket. I'll have to assess the pump more after I've got the fuel leak figured out.

KWKloeber · June 04, 2015, 12:15:14 PM

Quote from: kwaltersmi on June 04, 2015, 12:09:50 PM
Quote from: KWKloeber on June 04, 2015, 10:58:59 AMI hate to ask - was your bilge pump working!?!?

The float switch was up and the pump was switched on on the fuse panel, but it was not pumping when I arrived. I'm assuming the pump automatically shut off because of the diesel. Or it was ruined because of the diesel. I don't know how long the fuel was in the bilge since it had been 2.5 weeks since I had been at the boat.

I see no reason why it would shut off. Was just hoping you had it "off" for some reason, and it hadn't pumped a bunch of diesel overboard! The CG frowns on that.

kk

kwaltersmi · June 04, 2015, 01:10:23 PM

Quote from: KWKloeber on June 04, 2015, 12:15:14 PM

I see no reason why it would shut off.

I think some bilge pumps will not pump oil/diesel to prevent toxic dumps. This is from Rule on some of their pumps: "The pump and solid state water sensing switch are in a single, compact housing. The sophisticated switch senses the dielectric properties of water but will not pump oil."

KWKloeber · June 04, 2015, 01:56:06 PM

Quote from: kwaltersmi on June 04, 2015, 01:10:23 PM
Quote from: KWKloeber on June 04, 2015, 12:15:14 PM
I see no reason why it would shut off.

I think some bilge pumps will not pump oil/diesel to prevent toxic dumps. This is from Rule on some of their pumps: "The pump and solid state water sensing switch are in a single, compact housing. The sophisticated switch senses the dielectric properties of water but will not pump oil."

Yes, that's true - but it's the switch that "senses" oil present (i.e., doesn't make contact) on the solid state switches, not the pump itself, and not float switches. If the float-type was "up," I don't see why the pump would shut down.

kk

Ron Hill · June 04, 2015, 07:07:03 PM

kwalt : Sounds as though you have a fuel tank leak!
Take off the port side aft cabin panel and inspect the fuel tank and its plywood platform it sets on. Everything should be dry, but I suspect you'll have a wet platform.

Lift the float switch and see how high it must be to have it kick ON the bilge pump. Probably higher than you would think!!

You can run the engine with a fuel leak, but I think you have a static pin hole in the fuel tank.

You might want to recheck for a filter leak. Easy, just wipe a clean paper towel on the bottom and the on the top where the filter should seal. If it's stained you've found it.

You can do the same thing by rubbing a clean paper towel along a fuel line.

A few thoughts

Exodus · June 05, 2015, 08:16:07 AM

I recently had a leak also. It was one of the fuel lines on the engine. It also leaked under the engine and into the bilge.

Clay Greene · June 05, 2015, 08:40:51 AM

I will defer to the far greater wisdom here but if this was my boat, I would think the large volume of diesel all the way forward in the bilge combined with the recent replacement of the filters suggests that the filters are a more likely source of the leak than the fuel tank. A leak of that magnitude suggests to me that the fuel was under pressure; if so, the leak would be forward of the fuel pump. I would think that a pinhole leak in the tank itself would appear more slowly and would have been noticed by smell and/or seen under the engine bilge before it got to the main bilge. But that should be relatively easy to determine once you get the port wall panel off in the aft cabin and pull up the board looking down at the prop shaft/stuffing box. There is either going to be diesel there or not.

Very sorry to hear you are facing this problem. The smell has to be pretty bad.

kwaltersmi · June 07, 2015, 05:41:45 PM

Turns out the tank was the culprit. My wife and I ended up pumping the tank via the engine fuel pump and five gallon buckets (see pic below) until 2am to keep the bilge from filling with fuel (again!).

The next morning I disconnected and removed the fuel tank, which was much easier than I anticipated. I suspect the leak was coming from a rusty looking half-dollar sized spot on the port aft bottom section of the tank. There was also a pile of gooey/rusty looking debris and puddled fuel on the tank shelf directly beneath this spot.

So...Any advice on purchasing and installing a new tank? From my research here I've gathered that buying direct from Catalina (~$350?) is probably my best bet since the tank is the same size and the fittings are included (sending unit, pick-up tube, etc.). I understand that I may have to add a longer vent line and longer wiring for the sending unit.

My biggest concern is getting the engine started again after I install the new tank. I'm sure I induced air into the fuel system at some point in this process. I've never had to bleed my engine for fuel filter changes etc. since my M25XPB is self-priming just like the M35. Do you think I'll need to do a full bleed of the injectors, etc.? Any other re-starting advice?