Manifold Pressure Gauge PA_30

[George Kretschmann]

I just had the gauge rebuilt due to contamination in the right bellow in the gauge, the right needle was slow to move and would hang. So I got the gauge back me and the A&P installed it blew the line out for several minutes before hooking up the line and nothing came out so we assumed the line is clear. I made several flights and the gauge worked correctly and then the needle on the right engine started to move slowly and hang again. Air Parts says the bellow is contaminated again with fuel. My question is why all of a sudden is this happening? I hate to install it again without some kind of fix. Any suggestions? George

[Hank Spellman]

On the PA24's there is a tiny hole in the low spot of the manifold line. The purpose of this hole is to provide a tiny bit of airflow in the line so that any gunk that gets into the line is sucked into the engine rather than being pushed into the manifold pressure gauge. I assume that the twins have a similar hole for each engine. My bet is that it is blocked.

Hank
Henry A. Spellman

[George Kretschmann]

[George Kretschmann]

Here is what I found out about my issue with 100LL in the bellows of the Manifold Pressure Gauge. Apparently the metal line coming off the engine is a home made line. I called Webco and asked the question, why is there fuel in the gauge? I was told that the metal line, Manifold Pressure Line" should leave the head have a dip and then route up by the valve cover then over the valve cover to the rear of the engine where it is connected to the rubber hose going to the firewall. Also, that 4 inches from the head there should be a hole, .075" to be exact, to purge the line of any fluids collected in the dip. Long story short...I did not have the dip and I did not have the hole, both engines are the same. Thanks also to "AirPArts" for repairing the gauge for the 2nd time under warranty work. Thanks George

[N3322G]

Thanks for reporting back on the fix. Hats off to Hank for mentioning the international weep hole.