Fuel Starvation

Rocksteadee

Rocksteadee

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25 Jul 2011
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Fairline Turbo 36' Volvo TAMD61As
It would seem that I have a fuel starvation which required the air bleeding out
At 15 knots 2000rpm with half tanks lots of big air bubbles seen in Sepa filter causing engine to drop to tickover speed, no air bubbles for a few mins then engine picks up again, then air bubbles and slows again
Switched to both engines off one tank and ran ok

My thoughts are a hole in the tank pick up pipe halfway down or tank baffles broken away
Bugger to get to as floor has to come up
Assuming it is not a pipe leak as would occur with full tanks
Most grateful for any experiences of this or offers or someone give me another boat
 
sound like you have hit the nail on the head as you said i would say that it is the pipe from the tank to the fuel filter that is sucking in air under load. It has been know to be a just a simple as tightening the jubilee clips on the pipe end fixings stop air being sucked it.
 
Check the joints and tighten where necessary.

It could also be your pickups in the tank are blocked? Debris accumulates in a tank, swarf, hair, diesel bug slime etc and can block a pickup you could blow the wrong way down the fuel line ie the joint on the bpre filter back down to the tank with an airline or a dinghy pump and then re prime it.

I had exactly the same problem a few year ago on a pair of Volvo Penta 63's you were running at cruising RPM then the rev's would drop down by 500 to 800rpm then back up.

I had pair of these magnetic in line magnets for breaking up diesel bug fitted by the original owner , a series of ring magnets in a tube held in place with a spring and the whole thing was blocked up with crud.
 
A similar problem of air getting in , on boats with spin on fuel filters, can be caused by the filter not being seated correctly.
 
We had this problem last year in our Phantom 38 with same engines.
Removed stand pipe and found crud in the right angle connection,might have been there for years.
Hope this helps.
 
Stripped down relevant pipe work, not one piece of dirt was found
However I did find a compression fitting (compression nut over pipe with an olive) had sealant on the thread, which does nothing to seal the joint, just makes the thread tight and would possibly stop the nut from clamping the olive sufficiently. This could have been letting in air

Another thought could have been the castled bottom of the stand pipe may have been below the sediment in bottom of tank as the clearance was only a couple of mm. So have drilled a few holes 3 mm or so higher and stirred around in bottom of tank to clear sediment
 
Any offers on the best way to remove sediment from the bottom of the tank
Removal of the tank would be the last option as from what I can understand it involves taking the boat apart
 
Rocksteadee said:
Any offers on the best way to remove sediment from the bottom of the tank
Removal of the tank would be the last option as from what I can understand it involves taking the boat apart
Click to expand...

If you want to take a look at my set up and borrow my polishing pump feel free. Will be aboard OB Friday evening.
 
To remove crud, slime and bug.

The best is to open the tank up drain it and wash it out by hand,

Second best is to have it filtered and returned clean to the tank.
 
Spot on Bandit. It should be a criminal offence to sell a fuel tank without a/, a drain tap, b/. a removable plate big enough to get your arm in so it can be inspected and cleaned properly. I drain and clean mine every fourth year. All suppliers tell you their fuel is clean, but just maybe the tanks are not cleaned as often as they perhaps need. Unfortunately there are loads of boats with neither facility.
 
Rocksteadee said:
Being a turbo 36 I have heard that it would have been easier to have taken the engine out to get the tank out
Click to expand...

From what I've heard the tanks on Turbo and the Sedan can be removed with engines in situ BUT it involves a lot of dismantling of the woodwork sides etc. Not a job I would relish doing, and of course for maintenance purposes the original tanks won't have tank access panels or sumps fitted unfortunately.
Hope your problem turns out to be an easyish fix.
 
I used to have a Sedan 36 vintage 1983 with steel tanks.

I repo wavered her while the engines were out I replaced the tanks with larger ones 850 L each

The original tanks were steel and almost rusted through on the top

New ones were fitted with a one litre sump and a drain valve.
 
Floating Preferably said:
Spot on Bandit. It should be a criminal offence to sell a fuel tank without a/, a drain tap, b/. a removable plate big enough to get your arm in so it can be inspected and cleaned properly. I drain and clean mine every fourth year. All suppliers tell you their fuel is clean, but just maybe the tanks are not cleaned as often as they perhaps need. Unfortunately there are loads of boats with neither facility.
Click to expand...
Better place Fairline's Bernard Olesinski under arrest then !!!
 
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