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Fuel Starvation in rough water

3K views 16 replies 14 participants last post by  sailingdog 
#1 ·
I have a Jeanneau 43 DS with a Yanmar JH series diesel engine. The model is 4JH3(C)E 56 HP and it has run for only 600 hours.
I have had a recurring fuel starvation problem with the motor for the past 9 months.

In smooth water she runs like a dream.

In rough water the engine coughs, sputters and dies. It will start again and runs for a while but dies again. The engine runs for shorter and shorter periods between stall.
I have cleaned out the plastic 200L tank which had some sediment but no stickey gooey material. It is now clean as a whistle.

I changed the primary Racor filter which had some contamination but no water before setting out today, and during the time the motor was misbehaving. There was a slight improvement after the filter change but starvation and failure soon occurred again.
There was no water or other contaminants visible in the bowl.
I also changed the secondary filter on the motor.
This problem has me flummoxed. Everything is clean. So why the problem? The motor is "self bleeding" and has never been a problem before.
What should I do.
Cheers
Chris Morris
SV More Magic:confused:
 
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#2 ·
Maybe the rough weather heel is causing an airspot in your fuel tank or there may be sediment or something blocking the intake on the tank when you are at certain angles.
 
#4 ·
Another possible solution might be to have a fuel line running from the main tank to a small day tank. This might also be a good trouble shooting measure, since it would tell you if the problem is related to the existing fuel tank or not. If you don't want to go through the complications of installing a day tank, then I'd second Rockter's idea...since it's a pretty good one, and not that uncommon on diesel fueled boats. :)
 
#5 ·
Another risk of a pressurized fuel system is a run away engine. If your mechanical pump develops an internal leak (such as a hole in the diaphragm) the crank case can fill with diesel. This can cause the engine to run away at max RPM with no way to shut it down other than removing the air source (with a plug, or shooting a CO2 fire extinguisher in to the air intake).

I'm not saying a pressurized system is a bad idea, but I would have a CO2 extinguisher on hand and know how to use it to shut the engine down.
 
#7 ·
Will the engine run at full power when it is calm? If not then I would guess there might be a screen at the end of the pick up tube that is still clogged. If it does run fine in calm water I'm stumped. I would bleed the engine (completely) in any case.

John
 
#8 ·
A wee temporary gravity-feed supply... even an upside-down bottle or something would show you if there was a fuel problem. Just pull the line off the filter and rig a temporary feed. Even at the dockside it could be tested. Just have a friend replenish the temporary feed every few minutes while you load the motor in gear when tied up. If it runs OK, then it's a tank problem.
Perhaps try the pressurised fuel idea for $80.
 
#9 ·
A wee temporary gravity-feed supply... even an upside-down bottle or something would show you if there was a fuel problem. Just pull the line off the filter and rig a temporary feed. Even at the dockside it could be tested. Just have a friend replenish the temporary feed every few minutes while you load the motor in gear when tied up. If it runs OK, then it's a tank problem.
Problem is - if she "runs like a dream" in smooth water, she'll probably run like a dream alongside in the marina.

I have run from a canister directly to the fuel filters when I had a contaminated fuel tank and it runs perfectly well. Perhaps a properly secured jerry can while the water is rough will isolate the problem? And it doesn't have to be gravity fed - the lift pump will pull the fuel through. If it doesn't, that may be the place to look.:)

Andre
 
#10 ·
If the fuel pickup is rubber on the pickup end and if things are just right - copper, in rough weather - could be sucking itself to the bottom of the tank when healed. My first instinct is to say sediment from the bottom is mixing with good fuel but I have experainced a fuel pickup sucking itself to the bottom of the tank in a non-marine enviorment. A garden sprayer filled halfway with diesel fuel, pumped up and attached to the lift-pump would confirm if all went well, that the problem is in the tank. I like gravity feed and a day tank.
 
#11 ·
Facts

Fuel under pressure leaks and makes a mess and is easy to locate and most of the time is consistant.

An air leak is a hard thing to find. It will only show up with simptions or "I have tried everything else".

First you should check all fittings from the fuel tank to the lift pump, a loose fitting could be the cause.

Didn't find a loose fitting?

Take a clean white rag and wipe every fitting for any trace of fuel, give it sniff just to be sure.

No fuel?

Wipe the entire fuel line. What you are looking for is just a little seepage that may happen after you shut the motor down.

When there are no answers replace the fuel line from tank to the pump.

Rick:cool:

I have a Jeanneau 43 DS with a Yanmar JH series diesel engine. The model is 4JH3(C)E 56 HP and it has run for only 600 hours.
I have had a recurring fuel starvation problem with the motor for the past 9 months.

In smooth water she runs like a dream.

In rough water the engine coughs, sputters and dies. It will start again and runs for a while but dies again. The engine runs for shorter and shorter periods between stall.
I have cleaned out the plastic 200L tank which had some sediment but no stickey gooey material. It is now clean as a whistle.

I changed the primary Racor filter which had some contamination but no water before setting out today, and during the time the motor was misbehaving. There was a slight improvement after the filter change but starvation and failure soon occurred again.
There was no water or other contaminants visible in the bowl.
I also changed the secondary filter on the motor.
This problem has me flummoxed. Everything is clean. So why the problem? The motor is "self bleeding" and has never been a problem before.
What should I do.
Cheers
Chris Morris
SV More Magic:confused:
 
#12 ·
For what it's worth, my brother had the same type of issue on a new install his Yamar.

Turned out when they repowered they incorrectly ran the fuel return line (to the tank) from the filter instead of the end of the injector supply.

Hope this helps...
 
#13 ·
Chris-
"When you hear hoofbeats, think horses not zebras." Well, at least in most of the world.

But since your system seems to be OK in each piece, and just not right in rough wx, I'm wondering if something has been mounted in such a way (i.e. fuel lines bolted to the bulkhead) that when the boat and the engine move and shift in rough wx, that shifting is applying pressure on the fuel line, which is flexing some fitting just enough to allow it to suck in air.

Creating an engine stumble, with no signs of a leak and no problems when things aren't bouncing around.

It's a zebra, I know, but zebras seem to be making their way around. Maybe try running the engine at the dock, and getting a bit physical with all the fuel system and fuel lines, TRY to create that kind of an air leak. If there are any crush washers that haven't been religiously replaced--they could be the culprits. Or any other fitting that just isn't quite to spec.
 
#14 ·
i think an electric fuel pump is a good thing to have. i have one for the yanmar 2GM20F in my nimble 30 Express. it is between the tank & the racor & makes bleeding air out the system easy. i was delivering a 50ft shannon ketch from SW harbor main to the virgins in november. we had a lot of water in the fuel tanks & it was blowing 40kn gusting to 57kn. when the water alarm for the racor went off i went back to the engine compartment & hung a bucket under the racor . i turned on the electric pump & cracked open the drain to keep bleeding out the water. if we didn't have the electric pump we would have been in trouble
 
#15 ·
You dont have to always run the electric pump either..I have one and my mechanical will pull fuel right through it..But as mentioned above they sure can come in handy when needed.
 
#16 ·
Thanks for the suggestions. The pickup is open copper about 1/2 inch from the bottom of the tank. The suggestion of 2 pickups is a good one given that the existing one is at the extreme end of the tank. I will check all lines from the tank for air leaks then fill the Racor filter and bleed the entire system before having another go in rough water.
 
#17 ·
Another place to check for air leaks is the banjo bolts on the engine. If the banjo bolts were overtightened or not tightened enough, the crush washers may be leaking air. They may also leak air if the mechanic removed the bolts and replaced them without replacing the crush washers.
 
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