out of fuel when still 1/3 tank

[PatAndEuan]

Recently experienced a problem with my fuel.

Was just heading out to cross the Strait of Georgia when the engine began to sputter. At full throttle could only manage 2000RPM. Occasional the engine would race then settle back to 2000RPM.

Tank indicator was showing 1/3 tank.. and this seems to have been reliable up until now.

Note that the Espar heater and Northern Lights gen set both seemed to be running fine, but I didn't run them for a long time.

Decided it was a fuel issue and when under sail proceeded to check the fuel system. Bled Racor filter bowl (seemed to be watery diesel) then the filter right at the engine. Fuel at the Racor looked better after the bleeding... so pressurized the system - note that there still seemed to be some bubbles at the engine filter when pumping... couldn't get steady fuel. Decided to start her up .. ran smoothly all of 30 second and then she died. Tried to pressurize the fuel system again, but no luck.

Removed the bowl from the bottom of the Racor again.. then opened the fuel tank stop cock to see if fuel was freely running to filter... after about 100ml of fuel the flow stopped. I removed the IN line to the Racor and blew the line to see if I could push fuel back to the tank... was a bit hard at first, but I could clearly feel I was blowing into the tank after a few hard puffs. ... and still no fuel flowing back down the line to the filer.

Became suspicious about the tank indicator so tapped on the poly fuel tank to get some idea whether there was fuel in there or not.. seem to be quite low (very hollow sound).. but very hard to tell near the bottom of the tank where it is curved. Being daylight I was unable to see where the fuel line was in the tank by shining a light on the top of the tank and looking at the side of the tank in the transom locker.

Wound up putting the zodiac in the water with my 9.9 merc and once we reach the other side (late because the wind was slackening) used it as a tug to get us to the slip in the marina. My guests were impressed by this manoeuvre, but I was pi%$ed off.

Next morning, convinced that the tank WAS empty I proceeded to fill the tank, but was surprised to find that it was topped up at 225litres!!! that's about 150litres short of a full tank. BTW, I always HATE filling the tank on the Hunter 466 because the tank vent and fill port are on the outside sloped part of the hull. I guess this means water can't pool around them (a good thing), but it also means any misjudgement in your fueling and the diesel foams all over the place.. including into our pristine BC waters!!! I visually verified that the tank was full when that evening I shone a light into the top of the tank and I could see the top of the fuel just below the top of the tank.

The next morning I pressurized the fuel lines as I've always done before (got fuel only - not foam - at the engine filter bleed nut by pretty much pumping the RAcor only) and started her up. Engine ran like a charm all the way home... 300PRM and 8 kts motor sailing the whole way with not so much as a hiccup.

So what is going on?

I do not know the mechanics of the fuel pickup in the Hunter 466's 100 gal tank. Is it on some kind of float system that rides on top of any water that might be in the tank, suggesting I have 150 litres of water or crappy dense diesel in the tank?

Note that a similar thing happened last fall, but when I bled the system after draining some water from the filters (changed fuel filters as well as they had not been changed sine I bought the boat in early 2006) all ran fine until this weekend.

Have been trying to find info about this on the net..no luck so far.

 

[Sailgunner]

You didn't mention changing the fuel filters.

 

[PatAndEuan]

I didn't change the fuel filters this time... they were new last fall... and the fuel wasn't flowing when there were no filters in line.. so what has me perplexed is why there was no fuel flow when the tank still had 150 litres of something in it...

 

[Benny17441]

Ok you may have determined that the gauge was not lying and that there was something left in the tank. What the gauge cannot determine is if that was good fuel or a water mix. You did not mention having replaced the filters so I will start with that. It has been my experience that whenever I find an undue amount of water in the separator the filter element also seems to get water logged and can easily clog causing the fuel flow to slow down until the engine sputters. At this point replacing the filter element is an easy but perhaps only a temporary fix. Make sure you use 30 microm filters at the Racor as the 2 or 10 microm may prove to be overly restrictive. The secondary filter at the engine is around a 15 microm and will catch any smaller particles. You are right, fuel should have flowed down the line by gravity alone. Perhaps you also had some obstruction at the pickup tube. A mixture of bacteria and water sometimes create globs that can clog any of the lines. I think you may need to clean the tank or at the very least polish the fuel. AS you probably know the fuel capacity as listed for your tank is not all usable fuel. There are always a few gallons that cannot be accessed by the pick up tube before sucking in air and this amount may vary as the boat moves more in disturbed seas. I also do not find gauges to be very accurate, they serve well as an indicator but would not rely on them to tell me how many gallons of usable fuel I still had on board. I use the hour meter, a fuel log and a tried and true burn rate for the engine to tell me that. cannot say for certain whether you have a good portion of contaminated fuel or you just exceeded your usable fuel capacity but I will bet you will find your answer in one of these two causes.

 

[Don Lucas]

Maybe a leak in the fuel suction line inside the tank.

 

[PatAndEuan]

I understand your questions and suggestions, so I'll try to elaborate:

Fuel filters
I did not change the fuel filters. How could it be an issue with the filters since now that I have topped up the tank the engine runs flawlessly. It did so for a full 6 hours yesterday afternoon on the way home. This would seem to rule out another blockage in the fuel line as well.

Fuel gauge
I completely agree that the one cannot rely on the fuel gauge, but in this case the tank was 150/378 litres full when I topped it up. The meter can't be that inaccurate. In the past, its estimate of how much fuel was left in the tank was pretty close.. for example, if it read I had 1/2 a tank, it would be full (backing up all over the deck) when I put 190 litres in there (50% of 378 litres).

So does the pickup float on the water at the bottom of good diesel in this kind of tank? So that if all that remains int he tanks is (150litres) of water, the tank appears empty at the fuel pickup?

Thanks for all your suggestions in advance.

 

[splax]

Don's suggestion that you may have a problem in the fuel pick-up 2/3 the way down the tank sounds insightful. I suggest removing and testing the pick-up for leak or degradation. The inside of the hose may have "bubbled" and blocks the intake by collapsing under suction without enough supporting pressure from the fuel level.

 

[PatAndEuan]

I'll pull the intake hose up and take a look at it tomorrow.. will let you know what I find out.

Thanks guys!

 

[Capt jgw]

And if there's a screen or filter on the end of the pick up tube, remove it. Let the Racor do the filtering, not the pick up screen in the tank where you can't get to it. It is possible that this screen is already plugged, and with the tank full and gravity assisting, the fuel will flow. As fuel is used, there's less weight pushing down, and flow stops. If that's the case, it won't be long before the fuel won't flow at all.
Also if you're getting water in the filter bowl, there's water in the tank, and there shouldn't be. Check the o ring under the filler cap, you can get a new one at any hardware store. It's very common for those to leak.

 

[Mikem]

This identical issue happened to a friend of mine who owned a 2001 generator equipped H460. The culprit was the depth of the engine pick up tube. It seems as though the pick up tube for the engine was set at the generator pick up tube level and vice versa. The engine pick up is supposed to be the deeper of the two tubes. The theory being that the engine should be the last to be starved of fuel. So check the depth of the two tubes. On my friend's boat they were reversed.

 

[waternwaves]

tank level indicator- or the acute lack therof

2008 Beneteau had a Yanmar 3YM30 with fue gage.

Gage read 1/4 tank, at rest in slip in Roche Harbor

53 minutes later at 3000 RPM fuel starvation. empty tank.

Time to sail into the gas dock at Deer Harbor. (I am sure it was more exciting for the powerboats at dock than it was for me)

SO, moral of the story
1. Don't trust fuel gages after someone else uses the boat or heater
2. Don't trust fuel gages to be accurate

 

[PatAndEuan]

This identical issue happened to a friend of mine who owned a 2001 generator equipped H460. The culprit was the depth of the engine pick up tube. It seems as though the pick up tube for the engine was set at the generator pick up tube level and vice versa. The engine pick up is supposed to be the deeper of the two tubes. The theory being that the engine should be the last to be starved of fuel. So check the depth of the two tubes. On my friend's boat they were reversed.

That's exactly the kind of thing I wanted to check... because I figured that the deepest intake should be the engine and not the gen set or diesel heater.

 

[PatAndEuan]

2008 Beneteau had a Yanmar 3YM30 with fue gage.

Gage read 1/4 tank, at rest in slip in Roche Harbor

53 minutes later at 3000 RPM fuel starvation. empty tank.

Time to sail into the gas dock at Deer Harbor. (I am sure it was more exciting for the powerboats at dock than it was for me)

SO, moral of the story
1. Don't trust fuel gages after someone else uses the boat or heater
2. Don't trust fuel gages to be accurate

I haven't been relying heavily on the fuel gauges .. the same system monitors my 5 fresh water and 2 holding tanks.. 2 of those sensors have failed. Some people have suggested I track fuel usage by engine hours... great idea when the engine or even the engine/generator are involved, but up here in the pacific Northwest we have diesel heaters on board (which probably use more fuel / year than the engine) and it is impossible to estimate fuel consumption of these heaters. So it is a strong light on the top of the tank at night to get a true measure of the fuel on board. I was so busy the night I arrived that I didn't do that check.. and I HAD to fuel up first thing in the morning.

Thanks again everyone... will let you know what I come up with.

 

[Stu Jackson]

Benny and Capt jgw's advice is spot on.

You wrote: it is impossible to estimate fuel consumption of these heaters.

No it isn't, and you should learn how to figure that out.

You could do a test by running each one for an hour and see how much fuel you need to replace (say from a 2 - 5 gallon jug you take along). You NEED to know these things. You could also install hour meters in their circuits.

Good luck. Fuel gauges are the devil's workshop, use your engine hours.

 

[Mikem]

As far as engine fuel burn goes on a recent 13 hour run I did a fuel check. Running at a constant 3000rpm the consumption was 2.08 gph. The heater is hard to gage...I have a Webasto and so did my buddy with the 2001 H460. As my buddy was a liveaboard in Bremerton, Washington he had his heater on 24/7 and figured on a gallon per day.

Also, the fuel consumption curves supplied by Yanmar I have found to be very accurate. 2000 rpm about 1gph at 6 kts, 3000rpm 2 gph at 8kts, and 3600rpm the curve says 3.6gph. Truly a severe penalty for maybe another 1/2 kt.

 

[Bill Roosa]

You might want to check the tank vent. Everything you describe could be caused by a tank not being vented to the atmosphere and making a suction lock. then you bang around the filler cap while fueling and push a lot of air through the vent and the problem magically goes away.