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Engine driven fuel pump cooling shroud... necessary? Original?

Immelman

By Immelman
in Vintage Mooneys (pre-J models)

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Immelman Mentor

Immelman

Posted
Posted

1966 M20E, IO-360-A1A.

There was an old thread on Mooneyspace on the topic but it didn't seem like a definitive resolution: is the cooling shroud necessary?

I had one on my airplane. It broke and was rattling around. Options: Replace, or mount the scat tube that fed it to blow air on the pump.

Looking at the Mooney parts manual, there is no explicit mention of the shroud. An 'adapter' is listed, but with an o-ring right after that can't be it, right? Looking at the Lycoming overhaul manual, no mention of the shroud is made.

I'm not sure what other literature to consult? IA signing the annual seemed happy to remove it and aim the scat tube at it.

carusoam Grand Master

carusoam

Posted
Posted

Cooling and insulating fuel system parts is always a good idea... nothing has changed with regards to 100LL evaporating and causing challenges with hot starts...

As far as what is supposed to be there for a cooling shroud... let’s check with the doc... @M20Doc

It appears that history may have changed the requirements over time... and some fuel pumps may have lost their cooling shrouds...

PP thoughts only, I have no recollection of any fuel pump cooling shrouds....

Best regards,

-a-

Immelman Mentor

Immelman

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Posted (edited)

I saw the spruce shroud, yes. Looks like a PITA to put that on, something to be done at overhaul. But what I am after is if I am "missing" anything important by doing the SCAT tube blast air.

- Not in the parts manual (unless I missed it elsewhere??)

- Not in the lycoming OH manual (is there another lycoming manual to consult?)

- At least one IA ok with it, that is but a single set of eyes and collective wisdom though!

- On the other hand maybe I missing an AD, SB, etc?? Perhaps more dirt digging needs to be done on my part.

I can think of a reason I'd like it OFF: to see the fuel pump! I'm correcting several oil leaks in the vicinity. The fuel pump is much more easily seen without the blasted can over it.

Edited by Immelman
Culver LFA Proficient

Culver LFA

Posted
Posted
5 hours ago, M20Doc said:

I’ve seen them with and without a cooling shroud, but believe that they were factory installed.  Aiming and securing the Scat duct at the pump is better than not at all.  In the absence of the Mooney shroud, you could put on one of these.

https://www.aircraftspruce.ca/catalog/eppages/fuelpumps.php?clickkey=6450

Clarence

 

That is the RV pump shroud sold on Spruce. This is the one I used to replace my worn out Mooney original. A couple minutes work with a few cuts here and there. Shorten the skirt so nothing rubs and elongate the holes so you can slide the cover over the top of the pump (instead of trying to fit the lines through the holes into the pump).

Highly recommended.

  • Like 2
Immelman Mentor

Immelman

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12 hours ago, Nukemzzz said:

My 66 E has what’s left of a fiber cloth cylinder with an aluminum lid on it with a port for scat tubing. It’s a very drafty old thing. Might be asbestos.  Lol

Sounds awfully similar..... the thing was rattling around loose. Not good in an area with parts vibrating to the tune of 4 IO-360 cylinders.

  • 1 year later...
outermarker Rising Star

outermarker

Posted
Posted (edited)

I too, have a beat up old fiber type fuel pump shroud that needs a major overhaul or replacement if I could find one. Mine doesn't have any attachment points which I find odd. It seems like it just sits there relying on the scat tube to hold it in place and not rattle around too much. The one Spruce sells looks like it uses the fuel pump bolts as the attachment points. I don't like the idea of having to remove the fuel pump bolts to remove the shroud so I can inspect the pump. Could the fiber material be baffling material? I also asked Lycoming about it and they said it was a Mooney part. However, as mentioned above the Mooney Parts Manual is no roadmap to success. 

Any thoughts on using high temp silicone? I can buy an 1/8" thick sheet and cut it to fit. 

Silicone Sheet, 70A Durometer, Smooth Finish, No Backing, 0.125" Thickness, 12" Width, 12" Length, Red 

Temp rating is 500F

 

Edited by outermarker
Immelman Mentor

Immelman

Posted
  • Author
Posted

I ended up removing it and rigging scat tube to point at the pump.

The darned shroud was shaking around doing damage to (cutting) the an AN fitting coming out of the pump. Screw that.

Raymond J1 Rising Star

Raymond J1

Posted
Posted (edited)
17 hours ago, outermarker said:

@Raymond. you drilled out the rivets, soaked some canvas with high temp silicone sealant and then riveted it back onto the top?

Not exactly.
yes, for disassembly I just had to drill the rivets.
On the aluminum part which is in Al.Mg 5 welded, there was a bit of boilermaking because the part was forced during an earlier disassembly and the upper part was pressed in.
For the "gummed canvas" (this is the general name given in France to these technical fabrics impregnated with rubber or similar).
In fact, originally, it is a fiberglass canvas impregnated with a mixed butyl-nitrile rubber, capable of withstanding 200 degrees and whose texture to the touch is "greasy", the rigidity of this 3 mm thick canvas is higher than that of silicone canvas.
The temperature limit is sufficient in this area of the motor and as it is written above, this gummed canvas construction and its rigidity / flexibility is important for the behavior of this part to vibration.
This speaker has been mounted on the engine since 1966, it has a little more than 5500 hrs of operation and I have not noticed any traces of particular wear on the crankcase, the fittings or even the part itself. The motivation for the reconstruction is only the hardening of the gummed canvas with time and temperature.
It is important that the ventilation "scat" sheath does not constrain the mechanical pump cover.
If you want to rebuild this part I can put here diagrams of the developed parts, with dimensions in inch or mm and photos.

Edited by Raymond J
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outermarker Rising Star

outermarker

Posted
Posted

Hi Raymond. Thank you for the offer and the insight to refurbishing this part. I feel many here would be interested in what you have done. If you can post with the dimensions in inches, that would be great! thank you!

Guest

Guest

Posted
Posted

Why not use an aluminum cooling shroud like Piper used in many airframes?  They’re available at Spruce.

Clarence

9FA92446-728D-4D8B-A1B9-BC3CE0DC10EB.jpeg

ArtVandelay Grand Master

ArtVandelay

Posted
Posted
I ended up removing it and rigging scat tube to point at the pump.
The darned shroud was shaking around doing damage to (cutting) the an AN fitting coming out of the pump. Screw that.

Where’s the inlet side of the scat tube?

Is this just an E model problem?
BobbyH Community Regular

BobbyH

Posted
Posted
On 4/11/2022 at 8:27 PM, Raymond J said:

It is important that the ventilation "scat" sheath does not constrain the mechanical pump cover.
If you want to rebuild this part I can put here diagrams of the developed parts, with dimensions in inch or mm and photos.

Raymond, that would be great, thanks for doing the ground work. 

Bob

Best to learn from others mistakes, you won't live long enough to do them all yourself. 

Raymond J1 Rising Star

Raymond J1

Posted
Posted

Ok, I'll post here the plans of the parts for make the same. I would put some details pictures too. I request just asking to all to wait a few days, I'm on the move for the job.

  • Like 1
Guest

Guest

Posted
Posted
40 minutes ago, outermarker said:

2m20doc...spruce doesn't have them in stock when I checked last week and not sure when they will have them.

 

Spruce Canada, shows one.

Clarence

Immelman Mentor

Immelman

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Posted
On 4/13/2022 at 5:59 AM, ArtVandelay said:


Where’s the inlet side of the scat tube?

Is this just an E model problem?

I do have an E, not familiar with what is under the cowl of other models.

On mine, there is a hole (as I recall), in the left rear side of the 'doghouse' baffling. A ~1" scat tube is clamped to that and was routed to the fuel pump cooling shroud.

  • Like 2

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