C205 Fuel Problems

C205 Fuel Problems

Hi

I'm one of the new owners of a C205 which is used for skydiving. On the first day of operations, we had the engine sputter in the landing pattern, and the pilot turned on the boost pump and switched tanks, after which everything was fine for that landing.  There was plenty of fuel in both tanks when this happened. 

On the next flight, the throttle was firewalled for takeoff, and the power climbed and then went immediately to idle.  We did not lift that load and took the plane to the mechanic. 

We did find some contamination of the fuel system and had the system flushed (it has previously been operated at a grass field with an older fuel bowser).  We also had the fuel manifold removed and inspected by an engine overhaul shop, and it was found to be in good shape with no problems.  Insualtion was added to fuel lines to help prevent vapour lock.  However, after these fixes and inspections, a subsequent full power runup on the ground saw the engine go to full power, then immediately drop to idle.

When we were looking at this aircraft, we had the previous owner come in and fly some loads for us, along with one of our seasoned pilots (an airline pilot by day).  The engine did quit at about 10,000 feet, but restarted with the boost pump and a tank switch. We attributed this to the fact that this operator liked to fly with very small amounts of fuel (<12 gal) on board, and we thought the tanks might be unporting in flight.  However, we usually operate with alot more fuel and thought this would not affect us.

The other interesting issue is that this previous owner had two bent cotter pins stuck into the vents of the fuel caps, and he told me they had to be there.  However, our mechanics removed these pins once we bought the aircraft, saying they were not an authorized mod. Our fuel system problems started soon after (admittedly this may be a coincidence).


We have operated C182s up to this point and have not run into a similar problem. Obviously we want this fixed, and don't want to take jumpers until we are sure we have found the cause of the problem.

Clearly the previous owner did have fuel problems as well, but convincd himself, or at least convinced us, that this was due to flying with very low fuel.

Would any expert out there care to speculate on this behaviour?  Could there be a fuel venting problem?  Is the 205 susceptible to any other fuel system issues?


Thanks in advance for any help you folks can provide!

Rod Berek
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Re: C205 Fuel Problems

I itnhk you're on the right track suspecting a fuel vent problem.  Maybe that's why he had the bent cotter pins in there!

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Re: C205 Fuel Problems

I agree with Walter.
When checking the fuel bladders, check the position of the vents.
How old are the fuel bladders?
Are you getting little black flecks in your fuel sumps?
Check the caps and make sure they are the proper caps for  your C-205.
Check for a flattened or kinked fuel line.
What is the condition of the float in  the carb?

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Re: C205 Fuel Problems

The in flight problem you describe does sound more like a venting problem as Walter and Clay suggest, however your ground run is what concerns me, and don't believe that to be a vent problem.

< "However, after these fixes and inspections, a subsequent full power runup on the ground saw the engine go to full power, then immediately drop to idle.">

I would check out the fuel line between the aux (electric) fuel pump and engine driven pump. It could be breaking down internally. They can have little pieces that fold away from the inside and act like a valve, partially blocking flow. The aux pump may be just enough to help blow it on open.

You have to visualize. Just and idea. Your problem warrants a thorough investigation.
Del

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Re: C205 Fuel Problems

Clay,
The 205 has the IO470 and I just thought of something else. Sometimes the diaphram in the flow divider can cause wierd problems.

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Re: C205 Fuel Problems

HI

Thanks for the replies. 

In answer to some of your questions:

*I'm not sure how old the fuel bladders are, and we did see some contamination of the fuel, but it was brownish flecks.

*The fuel caps are almost certainly not the correct ones, and this something I'm trying to fix immediately. 

*The aircraft is fuel injected.

You folks have given me some excellent leads on this problem.  I'll go back to the mechanic with these and we can begin to diagnose them.

You've made my membership pay for itself already!  Its greatly appreciated.

Rod

 

Rod Berek
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Re: C205 Fuel Problems

I must have had a momentary loss of mental function.  I knew the C-205 has an injected IO-470S Cont. engine.  No carburator.  BOY DO I LOOK SILLY!

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Re: C205 Fuel Problems

You don't look silly at all.  We all forget things.

As an update, we replaced and/or heat-shielded most of the fuel lines, then took it up for a 3 hour shakedown cruise.  It didn't miss a beat.  We are reviewing all of the info posted here (it has been given to the mechanic) as well as other research, and we'll make any remaining changes required.

Thanks again!

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Re: C205 Fuel Problems

You may also want to make sure the connections to the injectors are not leaking.
I had forgotten about the time it happened to me.

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