PA34 Owners Organization Forum Forums Aviation Interests Maintenance Fuel Selector Leak

Has anyone had their fuel selector valve overhauled? Mine is fine in normal position but has a slight leak in the crossfeed position. I assume its just a bad o-ring or the like but cannot seem to find which o-rings are used or any overhaul kits specified.

Interesting question. I will have to admit I almost "never" switch to crossfeed. My thinking is the "only" time I'd use crossfeed is in a single engine emergency. Right? Or are there other appropriate times to use.

In my three previous aircraft, all Cessna singles, I've always lived in somewhat trepidation of the fuel selector. Not wanting to have it malfunction I've never liked to play with them much. So that's carried over now to the Seneca.

However, I can appreciate that I should probably "exercise" it more often than I do so the capability is available to me in case of a single engine failure.

Where/how does yours leak?

I had been running on cross feed for a bit during run up, partially to not have the fuel in the cross feed lines be ancient stagnant fuel as you correctly pointed out the only real time you would do it is for extended single engine operations (i.e., already up shit creek). The leak occurs when the selector is in anything other than the normal position, the leaking fuel came around the inspection plate that gives access to the selector valve in the wing (just outboard of the gear).

The seller of the plane that I bought, as a technique, puts the valve positions to crossfeed during taxi out for a couple of minutes - both of them at the same time. I did not see that in the checklist, but it seems like a reasonable thing to do .......... is it in the checklist for some models?

Not on my checklist. Not that I’ve seen. I guess it’s a good idea to “exercise” this (as previously discussed).

I’m still leery, though, of playing with fuel selectors prior to flight. I’m more inclined to do the exercise post flight, perhaps while taxiing in or for fuel, etc. That would give the after-shutdown-inspection and pre-start inspection (next use) a chance to spot any leaks or abnormalities.

I don't switch prior to takeoff due to concern for fuel contamination etc. But I have heard the valve needs regular exercising to stay working. So I changed my checklist to switch after landing when I'm taxiing to the hangar- also makes sense since I am looking down there anyway to turn the heater to fan.

I think that the lack of exercise is that caused the issue with my valve. Smart to make it part of the post flight checklist to mitigate the contamination issue.

When you say "switch after landing," does that specifically mean you engage the crossfeed functionality for some period during taxi, then return the two fuel levers to their "normal" non-crossfeed position prior to shutdown?

Mine doesn't leak...yet. But it sat for a long time.

Does anybody have a recommendation for a shop that does good overhauls?

from what i understand its just a few o-rings that need replacement. What I think the bigger pain here is having to drain all the fuel tanks when the valve is removed

As a follow-up to the Crossfeed discussion,

Have any of you used Crossfeed on 1 engine while in flight to "balance out" one side?

Scenario:
Left tank: Down to 10 gallons
Right tank: 20 gallons.

(Why they might be unbalanced isn't relevant to the question, so don't worry about that).

With :30 mins of flight still to go, the 10 gallons on the left starts to get worrisome.
I considered switching to Crossfeed on the left only. But didn't do it because my confidence in the procedure was less than 100%.

Have any of you done this? What procedure did you use to do it in flight?

I had a complete top overhaul at one engine which results in a fuel flow of approx. 2 gal. per hour more on that engine the first 50 hours to keep the CHT in limit.

So I did that regularly during that time period to keep in balance.

Did you simply slide the fuel lever from "Full" to "Crossfeed" in one motion without stopping? Any risk of engine starvation in this procedure?

Just as!

To shut off, it takes some seconds (maybe nearly half a minute) to rest the fuel selector in the off position to shut down the engine - you may test that on ground.

I did “test” moving the cross feed levers on the ground while taxiing. All worked fine.

Ended up getting my valve overhauled during annual, mechanic said the old o-ring was so brittle it fell apart in his hands.