Fuel somehow siphoning from Tip Tank to Aux Tank in flight?

[William Flood]

Most every other little thing with my aeroplane I can get my head around. The PA30 was up for a solid 1 hour yesterday and flew great. All the TLC has paid off.

One niggle that I cannot figure out. I used the tip tanks for approx 5 mins to check their operation in cruise. I used 1usg from the right tip. Some how 6usg were burned from he left tip, but 5usg had siphoned into the left aux tank! So the extra 5usg went from the left tip into the left aux.

Sounds a bit mad but I'm sure mine isn't the first PA30 to demonstrate this problem. Does any one here know why this might have happened?

William

[Kristin Winter]

William,

I would bet that the solenoid valve is leaking, allowing the tip tank to flow into the aux as the tip tank is higher than the aux tank. Hopefully the seat of the valve is not corroded and you just need to blow some junk out of it.

Have you been getting my emails on the alcohol hoses?

[bernard nowlen]

What emails on alcohol hoses ? bernie

[William Flood]

Kristin was helping me out with some emailed images of the firewall forward alcohol hoses Bernie. If you want anymore info come back to me in a week, as I should have them figured out and operational by then.

[William Flood]

From reading the Tips on the fuel section it would confirm the theory that the solenoid is sticking on the left side due dirt or damage to the o ring. When you go to the trouble of draining the tip & aux for removing the solenoid it would be nice to put a new O ring in there? Anyone know what the O ring I've is? If I knew that I could have it bought and fit it when the mechanic goes to do the job.

William

[William Flood]

I wonder how you differentiate between a leaking tip tank solenoid, and a leaking fuel selector? I guess all you can do is to fix the solenoid and if it still leaks then it's the fuel selector.....

It's like owning a giant rubix cube this comanche business.


William

[N3322G]

William,

I suspect owning any aircraft is like having a giant rubic's cube - all designed to fly ... so far, none that I know of that are designed to be easy to maintain or diagnose problems.

FWIW, my guess would be the selector unless it has been attended to recently. I'll watch the outcome with interest as my twin also has tips.

[md11flyer]

Actually, it will not be the selector. The reason being there are 2 lines going into the solenoid, the Aux tank and the Tip tank lines and only one line going out, that line going to the selector.
If the solenoid is deenergized then the tip tank should be isolated completely from the fuel selector. But if the solenoid doesn't close completely then fuel can flow from the tip tank into the aux tank without going to the selector. The only time where you can get fuel leaking between tanks from a bad selector is between the Mains and the Aux and if selected the crossfeed.
You need to drain the aux and tip tanks and disconnect the lines to the solenoid and clean any debris in the solenoid. You can check the operation by blowing into the tip/aux ports and switching the selector from aux to tip. If you can blow air through the selector from the tip side when the switch is to Aux then you need to service the solenoid as it is not closing completely.

Hope this helps,
Gary

[William Flood]

Good man Gary,
You've just halved my problem. In the last few weeks I took the solenoids out and free'd them up as they were not used in this airplane in a long time. I got them working, and filled the tip tanks then drained a good bit of fuel through the lines to make sure there was no air in there. Then after I air tested it, I noticed the fuel vanished from the tip and gone to the aux. It must be some dirt I picked up in the system from draining it through so extensively. I'll go again and get the left solenoid out and try get a new O ring in there to see if it helps.

Glad it's not the fuel selectors, that would very $$$ intensive to fix.

Thanks folks