Rear engine fuel drains

[n86121]

1. Can anyone identify the various drain lines as below?

When topped off I have a steady drip from #2, at least.

If I can find some time will follow the lines up to wherever they go, but I thought others may also find this info useful.

From research, the fuel divider apparently has a 4 psi cut off that may not be cutting off, thus draining into and then from cylinders out the drains?

2. An A&P years ago routed my oil breather (fire sleeved etc) down and out as number 7 in the photo, to reduce breather drool onto rear elevator. After a long descent / flight I sometimes find drool on the cowl, apparently slimed up the passenger side by airflow.

When filled to only 6 quarts everything stays nice and dry. I filled to 8 for this weekend of 7 hours flying and noticed the drool. It is still at 8 qts, so maybe the answer is to leave it at 6 and only bring up to 6-7 when down to 5 qts?

a. Would I be better off with the breather NOT in the airstream,
as it may possibly be sucking out air/oil in its present position?

b. Any other recommendations?

Thanks

[patrolpilot]

Thanks for posting, very interesting. My airplane is in the shop now, will stop out of my patrol tomorrow and see if the cowlings are still off my aircraft.

[n86121]

1=
2 = pilot side cylinder drain
3 = pssgr side cylinder drain
4 = eng fuel pump drain
5 = elec fuel pump drain
6 =
7 = oil breather - relocated

[wslade2]

on mine, 1970 E model
#1 and #2 are the intake drains
so, yes most likely fuel probably from flow divider not cutting off. As the fuel pressure drops during shut down a spring loaded diaphragm is supposed to positively cut off the fuel.
do you "diesel" on shut down (fuel continuing to run into a hot cylinder, lack of positive shut off)?
does it drip with fuel overhead valves in the off position?
have you felt/smelled the drip (positively identified as fuel)?
Crankcase vent will blow oil out definition....(many variables on how much)
oil is lifeblood of engine. fly with what is recommended, not less. My manual says minimum of 7 quarts. As far as more than 7, I would rather wipe some off than run out.
If the "drool" has increased, be aware of causes increased crankcase pressure.

[hharney]

Could be fuel divider but also check your fuel strainer, identified by pulling the strainer and noting the drain it flows from. Those fuel strainer require some maintenance periodically

My engines settle in at about 7 quarts in the sump and one in the filter. My dipsticks read 6 when I have 7 in the sump. So it's important that you calibrate the dipstick too. Any more than the 7 and it's time to wipe it off

[wslade2]

Agreed about the fuel strainer. I recently had a pesky drip that required replacement of the plunger.

[n86121]

I think I have them all traced correctly now.
Believe it or not, many transition to firesleeved hoses so it is a bit confusing!
Retracing a bowl of red spaghetti backwards from each end.

When mixture in detent. Cleanly shuts idle.
Is definitely in full idle against the stop.

Doesn't drip immediately on shut down, takes a while before ...drip drip drip.

Drip from LR cylinders definitely stops w fuel closed overhead.

Still drops with newly overhauled flow divider from QAA.COM.
Still drips after a while, and then endlessly.
Flow divider spec only supposed to hold 1 PSI for 2 mins.

Thinking what else could be seeping fuel into cylinders, ...I thought of hand primers...?

Noted from your comments,
I discovered (after 25 years) that hand primers have a lock position.
I have used them so rarely, I never noted the actual detent position before.
Generally I'd just push them in and twist, but apparently not locked.

Fuel back on.
We will see if drip resumes with primer in detent.

[Kim Geyer]

There is a check Valve in the engine driven fuel pump return line it could be faulty and allowing fuel back up thru the system. I’ve seen it twice on our planes