Fuel selector Valve Locking

[pcesar2]

[MV Case Jr]

[pcesar2]

[Kristin Winter]

[Matt Kurke]

[Matt Kurke]

[Dave Fitzgerald]

Copied from other forum

Yes, but the 400 uses an Airborne valve so not a legit comparison. I installed a new valve several years ago and it too eventually got difficult to rotate. Believe it or not, there is no service procedure listed for the 400 valve other than cleaning the filter section; I replaced the gaskets and o-rings and lubricated it with "Fuel Lube"; problem solved.

No, the SCSM's only mention is "binding or leakage" as cause for service. Even searching the "Inspection Report" I find nothing other than the "drain and clean" mentioned.

If you load a CD of the parts catalog and service manuals onto your computer hard drive you also will have easy access to the data. Call me for a copy.

As per Tom; in my previous post I listed the sections where the lubrication is mentioned in the Single Comanche Service Manual, "In the SCSM section 8-15 engine oil is specified as the lubricant for the o-rings. Likewise in the SCSM mentioned in Table II-VIII - SPECIAL INSTRUCTIONS, "Petrolatum" Pure Oil Co code 5603 is specified."

Back to the Hoof valve and lubricant. I think engine oil is not a good choice, why would it not be washed away by the fuel, thus increasing the rotational force required and occluding the detent feel? The SCSM gives 2 choices - the oil is probably an error. And as I mentioned "Fuel Lube" makes for excessive turning force required in this style valve and no detent feel [although a good choice for the Airborne].

If you Google "petrolatum" you can find this reference http://www.chemindustry.com/chemicals/16752.html but I have not been able to locate a specific alternative for that specified "Pure Oil Co's code 5603 Petrolatum". Parker O-Lube is a petroleum grease; sounds kind of like "Petrolatum" to me. I got mine from Spruce.



Matt
http://www.comanchegear.com

[pcesar2]

Thank you for all contributions. They were the north to my observations.
Before I used the indicated grease to lubricate the o-rings, I have tried to understand the fact that the fuel selector valve was locking and after lubrication it worked properly but became hard again after avgas washed the lube, just to avoid masking the cause of the problem.

Looking carefully the surface of the valve plate, I observed a slight bending, indication that the plate was not rectified , probably caused by the angle made by the hand forcing the shaft through successive rotations.

The bending is the cause of the stiffness and sometimes locking of the valve, when it compresses the bottom site of the plate to the top of the fuel selector. I made a mistake thinking the o-rings were the cause of the problem, changing them.

Lubricating the o-rings solved the problem, but just to make the fuel selector safe to use, I uncompressed 1/4 of turn the 3 screws that locks the fuel valve. This keeps the valve plate uncompressed. No leak was found, after having checked the valve.

Regards,

Paulo