At last, fuel starvation problem solved

Wiggo

Wiggo

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After suffering from what appeared to be intermittent fuel starvation on the port engine for some while, I finally located the fuel pickup pipe on the tank and extracted it this afternoon. And what came out? Several big wads of plastic swarf:
2010-05-02140636.jpg
 
Lazy boat building/ers...drill the holes for the pickup(s) and not hoovering out the tank before fitting all the pipes! Its quite common....!
 
Years ago, when I used to drive to the Middle East, my truck would stop, every few 100yards. I cant remember how many times I took the pipes apart, even drained the fuel tank on a garage forecourt. Pulling pipes to bits 500 miles down a desert in a sand storm was not fun. The thought of losing something, or breaking anything, did not bare thinking about.

Eventually I found it. A little twig kept going up the pick up pipe and blocking it at the elbow. Each time I undid a nut, it dropped back down to the bottom again, and so it went on for thousands of miles.
 
When I used to fly for BA, one of our 707s came out of a major check, and soon afterwwards began to suffer a flame out on No 4 engine every few hours into the cruise. No reson could be identified. Fuel control unit changed, all ground checks OK, but it would still occasionally flame out in the cruise.

What was the problem they eventually found? When the engineer was inspecting the inside of the fuel tanks during the major check, he'd taken a small carpet to lie on. Not removing the carpet meant there was, in efect, a big flannel loose in the tank. Eventually it would find its way to the the fuel outlet and block it (like a flannel in a bath). When the fuel pumps were turned off and the outflow flow stopped it woulf float away, ready for another day....
 
Ah good old Sealine, when they went with plastic tanks on the F37 they knew about this early on and had several boats back to sort it out, obviously yours choose to take a long time and naturally when out of warranty to manifest!! Grrr - That's boating!!
 
When I worked in the power station at the local steelworks,they bought some 3Mwatt gas turbine generators based on the same engine that powered the Britannia aircraft.We used these for peak lopping,they would pick up 3mwatts almost instantaneously.One of them would pick the load up then drop it instantaneously,quite embarrasing at the time,just when you wanted the power ! It was traced to a foreign body being picked up.They used to clean the turbine blades by throwing in walnut shells,is this still done?
 
Bu99er! Spoke too soon, the problem's still there. Looking at the lift pump next. Can anyone confirm: on a KAMD43, if I open the bled screw on the fuel filter while the engine is ticking over, it should spew fuel out, shouldn't it?
 
Wiggo, When you say the problem is still there, what are the symptoms? I really mean when does it show most - at steady cruise you lose power and the revs drop or when under acceleration?
 
Wiggo said:
Bu99er! Spoke too soon, the problem's still there. Looking at the lift pump next. Can anyone confirm: on a KAMD43, if I open the bled screw on the fuel filter while the engine is ticking over, it should spew fuel out, shouldn't it?
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I would expect it to suck air in as that is how a cracked pipe acts and then produces engine surges among other things but I dont know.

You have clearly identified a source of blockage and cleared some big debris from the pick up, I would assume smaller debris headed into your fuel pipes first and some would get lodged higher up than the pick ups.
Have you tried to connect a dinghy foot-pump to the fuel line (fuel filter end) and blow it back into the tank or preferably take the pick up out again and blast it into a bucket.
 
I cleared the pickup on Sunday but didn't have time to test her. When we took her out for a test run on Monday, the port engine will still only reliably rev to 3200 rpm. She will pull to 3400, but hunts about randomly between 3200-3400.

I removed the fuel lines between the pickup and the water separator/primary filter and there was no more debris to be found. They've all been thoroughly blown through.

I then thought it was worth bleeding the system, so I cracked open the bleed screw on the port engine filter and pumped with the handle under the lift pump. This produced a froth of bubbles, but no fuel. I removed the screw and pumped, and there was no fuel coming out at all, so I replaced the screw and fired up the engine. She idled OK (but she would have been running on the fuel in the filter), but again cracking the bleed screw oipen produced nothing. Shut down, pump by hand, nothing. There is obviously some flow from the lit pump, as we can cruise all day at 3200rpm...

Is it possible the pump has been damaged by trying to draw against the obstruction for too long? No sign of fuel leaking from under the lift pump, either, FWIW.
 
Wiggo said:
Bu99er! Spoke too soon, the problem's still there. Looking at the lift pump next. Can anyone confirm: on a KAMD43, if I open the bled screw on the fuel filter while the engine is ticking over, it should spew fuel out, shouldn't it?
Click to expand...

I had the same problem on an F37 I used to own. The port engine would not achieve full revs. It was the Fuel supply pipe from the port tank. Replaced the pipe and fine as the rubber inside the pipe had started to "flap". As said on here - try and blow this pipe back and into a bucket and then try and blow the pipe the other way in the direction of the flow.
 
Would it be feasible to swap port and stbd pumps and filters and see if that narrows the problem down? Probably a real PITA but apart from buying new bits and just trying stuff, maybe one way of identifying where the problem may lie?
 
nedmin said:
When I worked in the power station at the local steelworks,they bought some 3Mwatt gas turbine generators based on the same engine that powered the Britannia aircraft.We used these for peak lopping,they would pick up 3mwatts almost instantaneously.One of them would pick the load up then drop it instantaneously,quite embarrasing at the time,just when you wanted the power ! It was traced to a foreign body being picked up.They used to clean the turbine blades by throwing in walnut shells,is this still done?
Click to expand...
We used to do it roughly like that in 1992
Stu
 
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