Running Diesel tank empty?

[dennismenace111]

Unless you have a burning desire to be cleaning your fuel filters on a regular basis, I wouldnt do that unless it was an emergency. I try never to let my tank get down below 1/4 full.. No matter how hard you try...no matter how many different fuel additives you put in your tank, there will always be gunk in the bottom... No need to go looking for trouble. It will find you all by itself given the opportunity.

Fuel burn per hour really doesnt change unless you change the horsepower you are using... ie..the higher the RPM, the more fuel you use. Regardless of how the wind is blowing or where the waves are hitting you. So think of fuel burn as gallons per hour at a particular RPM. You actually may find the information on line from your engine manufacturer.

[Squanderbucks]

Consider getting a Hart mechanical fuel gauge. No wiring or electrical hookup required. Works on air pressure. I have one as backup to others that connect to Nmea 2000 network - they are for convince. The Hart is backup.

[JPA Cate]

Hello, txg,

Because it can be impossible in some rough seaways to transfer 20 liters of fuel, it would be better to put it in while the wx is mild, and after there's room for it. The poster above who suggested you average all your combined fuel consumption is on the right track with that. Say 20 liters gives you 10 hrs. Then, keep track of the engine hours, and aver you've run it 15 hrs., there's going to be room for your final, emergency tank, any time after that. You want to make the transfer when it's calm and controllable, for instance if you took a berth in a marina, or spent a night at anchor.

Keep records. Install an engine hour meter if you don't have one. You could consider a reading of a 1/2 tank of fuel on your existing gauge to be the sign to add your extra 20 liters. By keeping track of the hours run, you should be able to work out when you will run out, and plan to fuel up well before. There is no need to run the engine out of fuel for any of this.

For what it's worth, you can often make a dipstick for your tank, it is how we check ours. Pumped all the fuel out into containers, and put it back in, filtering it as we went. Dead simple, cheap, but a fair wee bit of work, and you wind up borrowing a lot of 20 l. jugs. We can also (with another dipstick, of course) dip our water tanks.

The dipstick serves as backup to keeping track of engine hours and fuel input.

Ann

[Simi 60]

Originally Posted by dennismenace111

Unless you have a burning desire to be cleaning your fuel filters on a regular basis, I wouldnt do that unless it was an emergency. I try never to let my tank get down below 1/4 full.. No matter how hard you try...no matter how many different fuel additives you put in your tank, there will always be gunk in the bottom... No need to go looking for trouble. It will find you all by itself given the opportunity.
.

Sounds like you have a tank, filler point and supply issue.

* We use zero additives
* Tanks are rarely over half full
* We have zero crud in our tanks (we have a crud sump with drainage port at the lowest point of the tank which we sample 4x a year)
* Our fillers are 2 feet above the deck and never see water and O-rings are replaced at the first sign of degradation.

[Marc1]

Isn't a second fuel tank a good idea?

[jacktheflyer]

Originally Posted by Stu Jackson

I LOG all my refueling figures and stick 'em in my spreadsheet which calculates fuel consumption and how much I need to completely refill next stop, based on engine hours only.

This is rather simple.

I do this not only on my boat but on my cars as well. As in aviation you always need to have a secondary source of information and you take the worst one as true. I did however have an issue on my catamaran where I ran out on the stbd engine a couple of times as it was using half as much fuel again as the port engine. Found the pulleys on the alternators (tachos) were different sizes and so one engine was running much harder than the other.

I also have some gauges which are not very reliable. I ran donw both tanks to minimum and then pumped out each tank to get an empty reading on the gauges. They still aren't very reliable but that's beside the point.
scrubby

[Scotty Kiwi]

Originally Posted by S D Sailor

Please excuse my ignorance, but is it possible to shine a light into the inspection plate of a fuel tank and see debris or impurities? My tanks have a drain "tap" at the bottom (in a most inconvenient location under two bunk boards) and I've often drained a few cups to check for water. I've never had particles work their way to that drain....so how do I find if I have debris?
Also, I think there are baffles to keep fuel from sloshing (46 gallon tank)....which I'm sure impede debris "travel"....
Sorry if this is hijacking this thread....suggestions are welcome (even sarcastic ;-)

The fella that runs the fuel tanks dry on piston engine aircraft might wanna use a candle to inspect his fuel tanks. His kids might enjoy spending the life insurance sooner rather than later. If the bill was paid that is. haha.

[FlyingScot]

I'm with most here. I see no benefit and only harm, however minimum.

We installed poly tanks and marked every 20 liters as we filled them.
We removed the original fuel gauges to make room for a larger chartplotter.
We have bought, but not yet installed two N2K Maretron ultrasonic ones that should display on the CP when complete.
With only two 3YM30 Yanmars, we don't burn fuel very fast. We also keep 120 liters in fuel jugs above and beyond the two 170 liter fuel tanks.

[a64pilot]

Originally Posted by Scotty Kiwi

The fella that runs the fuel tanks dry on piston engine aircraft might wanna use a candle to inspect his fuel tanks. His kids might enjoy spending the life insurance sooner rather than later. If the bill was paid that is. haha.

Why do you say this?
Why would you think it unsafe?
Explain please.

[Frank999]

I vote with those who think the addition al wear and tear would be trivial.


However, you could solve the problem with a fuel management system. If you already have networked electronics, you might need only to add fuel flow sensors. I have a motorboat with such a system. It is incredibly accurate, and I can read fuel on board on my networked Garmin displays, which inherently know how to use the data.

[a64pilot]

Most modern gas engines actually calculate fuel flow, and they are very accurate to, they know engine rpm and injector pulse width and can calculate fuel flow.
To actually measure fuel flow on an old pre common rail Diesel requires two fuel flow measuring devices, as the return fuel has to be subtracted to get actual fuel burn.
Flow scan is a good brand, but they aren’t cheap. They can be very accurate though, especially if calibrated.
They can often be connected to a GPS and give very accurate mileage and range too.
Way more money than most of us want to spend and most of us don’t need absolute accuracy.

[Mithril Bham]

I may have missed something but you might get a stick. I never trust fuel gages. Second on the sludge.

[a64pilot]

Any fuel tank that has a dip tube to draw fuel from like I’m sure all of our boats do, running a tank low or out of fuel will not pick up any extra trash, that’s a myth.
The reason it won’t is the dip tube is always at the same place in the tank, and unless you have floating trash in your fuel the dropping level won’t cause any trash to be picked up.

[a64pilot]

And in case anyone was wondering what happens in a single engine piston airplane if the tank is run dry or the fuel switched off, the answer is not much.
If your cruising along at say 120 kts and the engine runs out of fuel, and you take no action at all, the nose of the airplane will drop a little so that the airplane hold approximately 120 kts, the engine will continue to spin as the wind is windmilling the engine. If you turn the fuel back on, the engine begins to run and the airplane will level out and fly at 120 kts.

Even if you intentionally slow the airplane way down so that the engine stops, simply putting the nose down will cause the engine to turn again as the wind drives the propellor, when it gets fuel again, it will run all by itself, you don’t even have to start it.
https://vimeo.com/268448424

Any pilot has hopefully been demonstrated the vast difference in glide ratio with a stopped prop as opposed to one windmilling. like spins and spin recovery isn’t required anymore but should be. The first time you see a spin shouldn’t be when you have inadvertently gotten yourself into one and are now trying to save your life.

[boat driver]

Originally Posted by txg

Like most boats we have a rather inaccurate fuel gauge and carry extra fuel in jerry cans. We did several trips >1000nm this year and when it was lighter winds it was kind of hard to plan on our fuel consumption. We know that our fuel consumption averages about 2L/hour, but there are big differences between motorsailing down wind and waves or motoring into a swell without any wind. So we tend to stay on the safe side and stop the engine as soon as we believe we could be down to an emergency reserve.



Our Vetus diesel has a factory-installed electric fuel pump, so bleeding the engine is done by simply switching it on and waiting for a minute while listening to the alarm sound. No hand pumps or bleed screws. The engine is a Mitsubishi S4L, so a standard old-school diesel without fancy common rail or turbocharger stuff.



For the future, i would like to know if there is anything wrong about just using up all the fuel in the tank till the engine stalls and then refill with one last leftover jerry can (20L ~ 50nm range for emergencies and docking).



When i tried to google this problem, only car-related answers came up. There it said that the injectors can be damaged and fuel filters clogged when the tank is run empty completely because of debris in the tank. I know that our tank is absolutely clean as it gets a regular inspection and we used a lot of fuel this year so far compared to the size of the tank. In the last 6 months, the engine ran for 330 hours which equals to about 5.5 full tanks used.



Is there anything i am missing regarding engine damage? The process of refilling and bleeding the engine would take about a minute on our boat and we are talking about being far offshore on the open ocean, so there are no traffic problems or anything like that.

Interesting question and the commentary response.
For most diesels, the shut off valve essentially runs the pump out of fuel. So without seeing the actual pump design- I am reluctant to suggest it is harmful or not- It does add wear to the starter and if it was running hard it probably does not have sufficient opportunity for engine cool down prior to shut down.

How do you know when it runs out of fuel that it is not a clogged filter or pump failure or trash in the pickup but actually an empty tank.

From your statements though I have seamanship concerns- If you have the miles mentioned, then the average of motor use should be fairly consistent permitting you to get to the last twenty minutes before starvation.


This timing permits you to fuel at safe times vs bad weather.
This disciplines awareness of engine maintenance.
This assures that engine shutdown/battery charges/ etc are full as per expectation. Then when it does start coughing the recognition will be not normal.

In conclusion- if you are concerned about the practice (asking the question) but cannot assure the tank is empty- then what is the practical purpose?