Rear engine fuel drains

[n86121]

Looked up parts diagram and list
-40 check valve pump to manifold.
Will check that out.

Makes sense.

From the drawing
the check valve appears near / under the elec boost pump
In Engine compartment or inside firewall?
Hard to tell.

Will find it tomorrow.

Thanks!

[Kim Geyer]

On our T337H’s the check valve is under the headliner above the baggage door.

[n86121]

Found mine
Little red devil in front of rear oil cooler, oriented vertically
arrow down, into airframe (and I assume back to manifold and tanks)
Same?

Pulled, cleaned,
did a light sun n blow test.
Seemed OK
Re-installed.
No change.

That said, it relies on its internal spring to stay UP and closed, and spring is very weak.
So IN airplane might still drool?
So maybe replace anyway?
Later models they mount horizontally. Probably for that reason.

QAA.com says with mixture in idle cutoff,
light pressure in the flow divider and its check valve shouldn't really matter.
cutoff is cutoff.

Other ideas?

[wslade2]

crack the line going from fuel pump to "throttle" / flow control with mixture in off position, tank valve open. See if there is dripping. My expectation is there should be no flow (ie-cutting off the engine is achieved through no flow through the pump).

What I understand the purpose of diaphragm in the flow divider is, is to provide an "abrupt" cut off of fuel flow as the pressure drops from cutting fuel pressure via the mixture on the control on the pump. But it is not your "stop" of fuel flow. It just provides a clean break. Your pump should be the control that alters fuel line pressure or stops fuel flow.

[wslade2]

Having some work done so I went and checked my aircraft, and surprised myself.

I have no drips. With mixture off and tank open, cracking fuel line between pump and flow control/throttle resulted in quite a trickle of fuel flow. Same when cracking line between throttle and flow divider. So good trickle is the norm there. Norm pressure appears to be low enough that flow divider IS the final cork in the system.

This makes me wonder if your fuel drip is from some other source than primary fuel supply as you have new flow divider.

You checked check valve. Try cracking line on engine side of check valve and see if leak there. (I would think if it was problem though you may have seen fuel flow while you were servicing valve before.)

But I would be very suspicious of the primer. Primer injects fuel directly into the manifold at the "U-bends" near prop end of engine. You will see two small stainless steel lines that tie into the "U-bends" one for left and other for right bank of cylinders. Try loosening the flare nut and disconnecting those and see if there is a drip from there with tank open.

[wslade2]

Also, sometimes the o-rings in the throttle control can shrink/set/deteriorate and there can be leakage around the shaft into intake. You would have to loosen the clamps to pull back the flexible intake tubing at the "Y" of the intake to detect that.

[n86121]

Interesting...

I bought an OVERHAULED flow divider from QAA.COM ($450 as I recall).

So assume it was done correctly. But you never know.

I still have the flow divider came out. I think it is newer, circa 2008 when engine was OH.

Maybe I should have it checked for pressure?
If the pressure on the old one okay, then the old/new OH divider not likely the problem.

Yes, check primer line next.

And hadn't thought of the throttle leakage possibility.

Probably good to check before pulling and send fuel pump (and $800+) to be 'overhauled.'

Any place one can suggest to more reasonably just get them 'pressure checked?'