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Fluctuating Fuel Pressure

Hi. Warrior -161, 160 HP D3G engine, 300 hrs on engine, 1000 miles from home, fluctuating fuel pressure, what to do?

Pressure falls from 5 to about 2.5 psi for a few minutes, and then appears to recover of own accord. Electric pump restores pressure to normal. After two excursions in 3 Hr flight, last our was normal.

Is this an immediate repair before next flight situation? Could it fail altogether?

Will call engineer in morning but hoping for answer on here due time difference. At Kjeller, Norway.

Thanks

EGBW / KPRC, United Kingdom

I don't know the fuel system on this one but if it was me I would not fly it at all.

It could be a failing engine driven fuel pump, but the intermittent nature of it is bizzare, for a mechanical system. Could it be that something has come loose?

Or there might be debris in the fuel system somewhere?

Administrator
Shoreham EGKA, United Kingdom

OAT when it happened? Were the tanks drained before the flight?

EGTK Oxford

Is 2.5psi still in the green range? If so, I'd continue the trip. You have two fuel pumps after all.

A group member reported this on our Jodel (O200) about 6 hours after maintenance. We flew it in the circuit, but it didn't show.The group consensus (no engineer available) was it was O.K. I flew it on the rear tank, in the climb, slow, near the airport until the engine died, then picked up as I dropped the nose, electric pump on, and changed tanks. I returned immediately. It was an air leak at the carburettor gasket, which had been off at the Star Annual. You could also have something in the fuel system. Unfortunately our present Jodel has no fuel pressure guage.

Maoraigh
EGPE, United Kingdom

The symptoms don't sound like a fuel pump problem. Any number of issues in the tanks, lines, filter, gauge, tank selector etc could cause those fluctuations.

I would not fly that plane until the whole fuel system has been stripped down and inspected - as a minimum.

If nothing is found then I would replace all possible causes of a fuel flow restriction.

I know this sounds drastic but this is not an area where it is safe to play around.

Hopefully some obstruction will be found when it is stripped down.

Administrator
Shoreham EGKA, United Kingdom

It was an air leak at the carburettor gasket, >

Mistake - it was the mechanical fuel pump gasket. (My post #5)

Maoraigh
EGPE, United Kingdom

Thanks for all the responses. My engineer said "indicator problem". Local engineer concurred. I'd notice any actual loss of pressure in the engine performance straight away and that hadn't missed a beat. Made a long overland flight yesterday with no problems and not a suggestion of any pressure loss. Tomorrow it's the sea (but plenty of Islands).

EGBW / KPRC, United Kingdom

I'd notice any actual loss of pressure in the engine performance straight away and that hadn't missed a beat

That assumption is hugely implementation dependent.

If you have a fuel system with a bit of "storage" then fluctuating input will not affect the engine - until it fails totally.

I could have all kinds of stuff like this on my fuel injected engine and it would run fine.

A suggestion: take the local engineer on the flight

Administrator
Shoreham EGKA, United Kingdom
19 Posts
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