Diesel smell from fuel tank

[Sputnik]

Thank you for your suggestions so far.
Getting to the fuel filler is a SOAB, so have not got that far up the filler pipe. I have ordered new filler hose (already replaced the breather hose, which was not blocked, even fitted a charcoal filter to remove diesel smell from the breather outlet) so will address that end when I replace it.
Yes, original fuel tank, boat is 3 yrs new to us, but always had this issue.
About to change all the waste hose for the same smell issue. Pushed the boat out and ordered the V expensive Vetus waste hose......hopefully worth the long term investment.
I installed an extractor fan for the engine bay as per a Hunter Mod' which runs all the time the engine is on, now thinking of fitting a 12v computer fan to run all the time we are on the boat to remove the smells, but that is not addressing the origin of the fault.
BTW, the fuel smell is not after refueling, it is after running the engine for some time.
Neil

[grahamb]

Hi.....believe that diesel fuel will fluoresce(glow) if an ultra violet lamp /torch is used.....cheap on the web....

[GeneM]

Some diesel engines leak at the injectors when cold under low pressure. Check if it's wet around the injectors.

[DeepFrz]

It sounds like you may have a very small high pressure leak as mentioned above. Could be around the HP pump or any of the HP fuel lines. Be careful though that you don't get fuel injected through the skin or in your eyes. The blue paper shop towels are good at showing where the wet spots are.

[Sputnik]

BINGO!

The new filler hose received, went to fit it to find that the aperture in the rear bulkhead behind the fuel tank for the hose to pass through is not in the correct place. I imagine that the filler hose was fitted to the tank, then the tank inserted into its bay & bolted down. Because of the miss-match it placed tremendous pressure on the side (bottom) of the filler hose. This stress has caused deterioration of the hose to the point that it leaches smell.
Very annoyingly the new hose was about 4" too short, so in desperation I cut off the damaged end and refitted it......no more diesel smell.

Neil

[Sputnik]

Oh dear, still got a smell.....
When I changed the fuel hose I also installed a computer fan on a 4" vent discharging air via a swan neck to the cockpit rear, this is doing a good job & has masked the fact that the smell is still there. I believe it's not as bad, but I am determined to stop it even if it means replacing the tank....
Catalina owners had posted a similar problem but the thread has dried up.
Neil

[Sputnik]

Further to my last post.....I think the smell I am getting is not diesel, but the rubber smell of the hose, which is quite strong and similar. It is genuine marine grade diesel hose.

I had a message from another 356 owner (similar age boat) with the same problem, so here is my response which may offer some more info':


Quote:
Renewing the filler hose has cured the problem, and I am finding I don't need the extractor fan on all the time now. BUT, the hose does smell very rubbery, which is a similar smell to the diesel, so we do the same with the cabinette holes & cover them with drink mats.

If you replace the hose you will need 2.5m of:

38Mm Rubber Marine Fuel & Oil Hose Iso7840 1 Metre | eBay

Getting the hose off of the neck of the tank is a PITA, you will need to lever it off with a long strong flat end screwdriver.


Use a hole cutter to relocate the hole such as:

ROLSON Hole Saw Set Cutter Down Light Holesaw Installation 51 60 65 72 75 85mm | eBay

For the extractor fan (you will need to grind/cut the corners off so it fits inside the duct adaptor ):

computer fan: Corsair 12CM 120mm Black Grey Fins Fan Cooler Case PC Computer Cooling 3 Pin | eBay

Hose adaptor: Ducting Tube Step Fan Hydroponics Reducer 3" 80mm 4" 100mm 5" 125mm 6" 150mm | eBay

Outlet vent: 3 INCH BOAT BILGE BLOWER PIPE 90 DEGREE BEND WITH STAINLESS VENT COVER | eBay

Hose: PU Flexible Ducting Hose - Premium quality - Ventilation, Fume&dust, Woodworking | eBay


I fitted the duct adaptor to a piece of ply which is screwed to the underside of the deck under the steering quadrant on the rudder stock, but it can be anywhere.

The outlet vent exits in the transom above the cockpit shower unit. (my engine vent is the same place on the other side) I have the vent elbow pointing upwards so it creates a swan neck. 1m of hose should be all you need.
Unquote.

I will post some pic's when I can get them.

[Sputnik]

Just tidying up some of my posts......
The fuel filler hose from the inlet on the stb rear to the tank was badly deformed during installation. I think the hose must have been fitted to the tank, and then the tank finally screwed down, the hole in the bulkhead did not align very well with the tank connector, this was putting a lot of stress on the hose. I re-cut the hole in the bulkhead to align better, and replaced the hose.
Since I replaced the fuel filler hose the smell reduced, and to a degree was replaced by the smell of the new hose which had a rubbery sort of smell that seemed similar to diesel......however, after about 18 months now I am very pleased to say that the hose smell has reduced, and I do not have any diesel smell.
Thank you to all who posted suggestions and comments.
Neil

[billknny]

Just a thought,

Are ALL the hoses (new and old) properly rated non-permeable fuel hoses? For inside a boat you should be using type "A-1" rated hose. It is expensive. The rating should be printed on the side of the hose. Type B-1 or B-2 will smell in an enclosed space. Regular "rubber" hose is NOT suitable at all. And if you used clear vinyl hose, shame on you!

The "wet rag" test is for sewage lines, and isn't reliable for finding smelly fuel lines.

[Sputnik]

The clear vinyl hoses are an abomination, and really don't have a long term home anywhere. No, all my hoses are high quality fuel resistant armoured.
The damp rag test does work on fuel hose, but it is difficult to tell the difference between the rubber smell and diesel.