Mailing List lml@lancaironline.net Message #34939
From: Gene Martin <genemartin@enid.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] Fuel Drains
Date: Fri, 17 Mar 2006 12:05:21 -0500
To: <lml@lancaironline.net>
Charlie.......O SO RITE.  there are 2 TCM SB's out on seal leaks. SB00-10 about coated seals pushing out and oversize housings. CSB01-1 about leak tests for installed pumps. One more thing to remember is that on the altitude compensating (auto leaning) IO-550 pumps the OLD drain is the sensing port for the compensating section of the pump.
Happy Trails
Gene Martin
----- Original Message -----
Sent: Wednesday, March 15, 2006 11:45 PM
Subject: [LML] Fuel Drains

Twice in a the last few weeks , I have found engine driven fuel pump drains with shipping caps installed.

 

It appears that mechanics/builders are not aware of the importance of installing a drain in the dry bay between the engine driven fuel pump and the accessory section of the engine.

 

Here is what is involved. If the seal were to fail in the engine driven fuel pump--raw fuel would go into the dry bay, and if the drain is capped, fuel will blow out the engine seal and go into the crank case.

 

Imagine with me. There you are at 24,000 feet, you may notice a slight drop in fuel flow, not much. Engine driven fuel pump pressure will be directed toward the engine seal / blow it out and go directly into the engine crank case. And oil will be diluted as it is contaminated with fuel.

After two or 3 gallons get into the crank case, how much lubrication do you think that will be?

What if,-- it just happened to ignite as the crank case overflows out into the turbos? Scary huh?

 

Here's a test. On your next preflight take two pieces of masking tape, and write "manifold drain" on one and "engine driven fuel pump" on the other. Get underneath your cowling and put the tape against the drain line that you believe to match the name on the tape.

Take the cowling off. Make sure that these two critical lines are properly identified--and installed--and DRY.

 

ANY fuel and out of either of these lines and you should not fly under any circumstances.

If fuel leaks through the manifold valve diaphragm, the engine may continue, repeat MAY, continue to run for several minutes with electric fuel pump on high. But if the diaphragm is split--eventually even high boost will not hold the valve open in the engine will stop.

 

We are so used to seeing fuel drain from the bottom of the cowling from the sniffle valve--that we ignore these other two drains which are critical.

 

Charlie K.

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