Clogged diesel tank vent

[Wxx3]

Thanks guys. I'll try all of the above. I suspect it's blocked due to "burping" of fuel near top off and no "weepage" at vent. Also, the port side always takes less fuel so I figure a blocked vent is causing a slight vacuum as fuel is used making the fuel flow from the starboard tank easier by comparison.
Thoughts?

Now that you mention the real issue, it's possible it's not blocked at all.

My tanks do exactly as you describe and the vents are not blocked.

I'd also try the shop vac blowing into your diesel fill (close valves to fuel lines etc)

 

[Wxx3]

#2 diesel has a minimum flash point of 125.6°F. In open air conditions, shouldn't be a problem. However, and as many industrial tank cleaners have discovered the hard way, it's not that hard to hit 130°F in a hot environment in a confined space. Think south Florida in August, 85-90°F injection temp, and an engine room after a several hour pull. Might get you there.

As with all activities, the devil is in the details. Way too many people treat diesel like it's water.

yeah, they do.

I've put out plenty of matches in diesel trying to start a heater. You should try it some time.

by the way, if you hinkt flash point is pertinent to this discussion, then with that line of thinking, all I would have to do is heat diesel to 130F and I don't even need compression anymore.

I wonder why nobody else thought of that first

 

[sbu22]

Just a guess, but I imagine you were trying to light the heater because the temp was less than 125-130F ?

The statement was regarding pulling vapor through a diesel tank vent line with non-rated equipment.

 

[stubones99]

Do a little research and you'll find that the first diesel engines had no injectors, but instead used a cloth soaked in fuel to atomize the fuel. Fire takes fuel + oxidizer + heat (spark). Anyone running a vacuum at night can see sparks in the motor of a vacuum.

now you know, do with the knowledge as you wish.

 

[Chrisjs]

Surely if the tank vent is really blocked the engine will eventually suffer fuel starvation?
I one saw a vessel with a seriously beer-canned water tank after being partly evacuated by the water pump while the vent was closed. Perhaps there is no need for the vacuum anyway??

 

[Bacchus]

I've had success w/ wet dry vac sucking on diesel vent to free it up.
I resisted blowing as it would push whatever is blocking it into the tank

I'm now sorry I even posted this...
If you are a gasser certainly don't do this.
If diesel and you are concerned also don't do it.
I will try to refrain from posting such controversial recommendations...however I will continue to use fixes that worked for me and didn't result in catastrophies

 

[Bacchus]

I would be careful vacuuming a fuel line, since that might pass fuel vapor past the motor with sparks from the brushes... kaboom!

#2 diesel has a minimum flash point of 125.6°F. In open air conditions, shouldn't be a problem. However, and as many industrial tank cleaners have discovered the hard way, it's not that hard to hit 130°F in a hot environment in a confined space. Think south Florida in August, 85-90°F injection temp, and an engine room after a several hour pull. Might get you there.

As with all activities, the devil is in the details. Way too many people treat diesel like it's water.

So I'm thinking that you guys should pass this info on to ABYC and convince them that ignition protected engine room equipment really is required for diesel powered boats / gennies...

 

[sbu22]

OK - #2 diesel is mother's milk. Ignore the caveats I stated. I frankly don't care what ABYC's positions on ER protections are. It does not alter the physical characteristics of the material. I suppose, in your eyes, that ABYC's opinion negates several instances that I have personally observed involving #2 diesel igniting in vessels, rail cars, and storage tanks. Guess it didn't happen and I didn't fight the fires. Must be getting old. Better, why don't you ask ABYC for an opinion of placing a diesel vent under a vacuum that potentially streams vapor through unrated electrical equipment? I'm not telling anyone to do anything. I am suggesting a thoughtful evaluation of site conditions in the context of planned activities. Sheesh!

 

[Conrad]

Don't forget that as the pressure is reduced via the vacuum that the flash point of the diesel will also be reduced.

 

[Robvald]

I've had success w/ wet dry vac sucking on diesel vent to free it up.

I resisted blowing as it would push whatever is blocking it into the tank

I've had good success as Bacchus and even better when you put the vac hose on the vent and remove the fill cap. A zip tie or wire to free up debris helps too. Good luck

 

[Moonfish]

I resisted blowing as it would push whatever is blocking it into the tank

^^This! ^^

 

[Al]

How do you measure your fuel tanks? Said to those who do not have sight gauges built in to the tankage. Often it is with a stick. Is our case, we discovered that the vent line was plugged to the point of no return. We have a specific 3/8th plug designed to allow measuring during filling. With the plug out, there is no vent issue. With it in, what ever, there is no vacuum created to stop fuel flowing.Assuming there is enough vent to allow for escaping air The suggestion is a separate access such as described.

Al-Ketchikan

 

[olegreg]

I discovered that that I had a clogged vent with a blowback during fueling. Geyser went 10' in the air. Diesel every where. Cleaned up the teak with a 100 lbs. of cat litter.
Yard had to replace the vent, though.

 

[SKS]

Hi guys,
Somehow this thread I started last Fall came back to life. Interesting discussion though. I ended up using the shop vac and SS wire methods.
I'm not 100% sure that was even my issue. I was thinking it was a possibility due to having a fuel imbalance at refill time. It might just be that my diesel return goes to the port tank only. I still don't know for sure.
Either way thanks to everyone. I really enjoy and learn from the "back and forth".
Steve

 

[Chrisjs]

Be very careful if you are not sure where your return flow goes to!!

Depending on engine type there could be a significant volume of fuel flowing back that might overfill a tank if feeding from one or more to only one (the wrong) tank.

I would get up close and familiar with your fuel valves. Do not ask how I know this!!

 

[SKS]

Thanks Chrisjs,
Thanks for the advice the you seem to have acquired the hard way. My single Cummins doesn't return enough fuel to cause a problem. It's just that I have observed that the port tank always takes less fuel to top off than the starboard tank. Also, it tends to "burb". Still learning the boat which we acquired Mid Summer last year. Thanks again to you and all those sharing their knowledge.

 

[Chrisjs]

Hi SKS
Not sure what Cummins engine you have, but unless I misunderstand something it looks like our 6BTA5.9 returned about 70gph to the tank!! Flow rate to engine (73gph) vs consumption of 2.5gph. See Cummins specs below. That is a lot of fuel over the course of a couple of hours!! Perhaps your engine is different. My over sight occurred with an early morning start to meet the tide in the Delaware Bay, and resulted in several gallons of diesel spilled. Most of it was recovered, filtered and re-used.
https://www.sbmar.com/docs/performance-curves/6BTA%20%5B330,2800,1975,HO,Nov%2000,M-90208%5D.pdf

 

[SKS]

Hi Chrisjs,
Very interesting. We have a 6BT, so probably similar.
I am not a diesel expert but if over 95% of the fuel flow to the engine goes back into the tanks, our set up surely allows return to both tanks and my imbalance issue is either vent related or the return favors the port tank slightly.
Thanks
p.s. If you would care to elaborate, am I to understand that you started out with full tanks and the return overflowed somewhere? Bilge, overboard? How did you "recover" the fuel?

 

[dhays]

Hi Chrisjs,
Very interesting. We have a 6BT, so probably similar.
I am not a diesel expert but if over 95% of the fuel flow to the engine goes back into the tanks, our set up surely allows return to both tanks and my imbalance issue is either vent related or the return favors the port tank slightly.

It could also be that you draw favors the starboard tank slightly? My water tanks mimic the fuel tanks, i.e. I have a tank on either side of the boat. Normally I have both water tanks open, but there is asymmetric use of the water. The port tank always gets drawn down more than the starboard. The same could be true for you fuel tanks.

 

[SKS]

dhays,
I like that thought alot. Means I have not problem to deal with. Clearly a "half full" analysis.
Cheers!
Steve